1
|
Tan X, Dou D, Chua LL, Png RQ, Congrave DG, Bronstein H, Baumgarten M, Li Y, Blom PWM, Wetzelaer GJAH. Inverted device architecture for high efficiency single-layer organic light-emitting diodes with imbalanced charge transport. Nat Commun 2024; 15:4107. [PMID: 38750042 PMCID: PMC11096390 DOI: 10.1038/s41467-024-48553-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/04/2024] [Indexed: 05/18/2024] Open
Abstract
Many wide-gap organic semiconductors exhibit imbalanced electron and hole transport, therefore efficient organic light-emitting diodes require a multilayer architecture of electron- and hole-transport materials to confine charge recombination to the emissive layer. Here, we show that even for emitters with imbalanced charge transport, it is possible to obtain highly efficient single-layer organic light emitting diodes (OLEDs), without the need for additional charge-transport and blocking layers. For hole-dominated emitters, an inverted single-layer device architecture with ohmic bottom-electron and top-hole contacts moves the emission zone away from the metal top electrode, thereby more than doubling the optical outcoupling efficiency. Finally, a blue-emitting inverted single-layer OLED based on thermally activated delayed fluorescence is achieved, exhibiting a high external quantum efficiency of 19% with little roll-off at high brightness, demonstrating that balanced charge transport is not a prerequisite for highly efficient single-layer OLEDs.
Collapse
Affiliation(s)
- Xiao Tan
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Dehai Dou
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Lay-Lay Chua
- Department of Physics, National University of Singapore, Singapore, Singapore
- National University of Singapore, Department of Chemistry, Singapore, Singapore
| | - Rui-Qi Png
- Department of Physics, National University of Singapore, Singapore, Singapore
| | | | - Hugo Bronstein
- Department of Chemistry, University of Cambridge, Cambridge, UK
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - Yungui Li
- Max Planck Institute for Polymer Research, Mainz, Germany.
| | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | |
Collapse
|
2
|
Sachnik O, Ie Y, Ando N, Tan X, Blom PWM, Wetzelaer GJAH. Single-Layer Organic Light-Emitting Diode with Trap-Free Host Beats Power Efficiency and Lifetime of Multilayer Devices. Adv Mater 2024; 36:e2311892. [PMID: 38214416 DOI: 10.1002/adma.202311892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Indexed: 01/13/2024]
Abstract
Organic light-emitting diodes (OLEDs) employing a single active layer potentially offer a number of benefits compared to multilayer devices; reduced number of materials and deposition steps, potential for solution processing, and reduced operating voltage due to the absence of heterojunctions. However, for single-layer OLEDs to achieve efficiencies approaching those of multilayer devices, balanced charge transport is a prerequisite. This requirement excludes many efficient emitters based on thermally activated delayed fluorescence (TADF) that exhibit electron trapping, such as the green-emitting bis(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)methanone (DMAC-BP). By employing a recently developed trap-free large band gap material as a host for DMAC-BP, nearly balanced charge transport is achieved. The single-layer OLED reaches an external quantum efficiency (EQE) of 19.6%, which is comparable to the reported EQEs of 18.9-21% for multilayer devices, but achieves a record power efficiency for DMAC-BP OLEDs of 82 lm W-1, clearly surpassing the reported multilayer power efficiencies of 52.9-59 lm W-1. In addition, the operational stability is greatly improved compared to multilayer devices and the use of conventional host materials in combination with DMAC-BP as an emitter. Next to the obvious reduction in production costs, single-layer OLEDs therefore also offer the advantage of reduced energy consumption and enhanced stability.
Collapse
Affiliation(s)
- Oskar Sachnik
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Yutaka Ie
- Department of Soft Nanomaterials, Nanoscience and Nanotechnology Center, The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Osaka, Ibaraki, 567-0047, Japan
| | - Naoki Ando
- Department of Soft Nanomaterials, Nanoscience and Nanotechnology Center, The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Osaka, Ibaraki, 567-0047, Japan
| | - Xiao Tan
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | | |
Collapse
|
3
|
Sachnik O, Tan X, Dou D, Haese C, Kinaret N, Lin KH, Andrienko D, Baumgarten M, Graf R, Wetzelaer GJAH, Michels JJ, Blom PWM. Elimination of charge-carrier trapping by molecular design. Nat Mater 2023; 22:1114-1120. [PMID: 37386064 PMCID: PMC10465354 DOI: 10.1038/s41563-023-01592-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 05/25/2023] [Indexed: 07/01/2023]
Abstract
A common obstacle of many organic semiconductors is that they show highly unipolar charge transport. This unipolarity is caused by trapping of either electrons or holes by extrinsic impurities, such as water or oxygen. For devices that benefit from balanced transport, such as organic light-emitting diodes, organic solar cells and organic ambipolar transistors, the energy levels of the organic semiconductors are ideally situated within an energetic window with a width of 2.5 eV where charge trapping is strongly suppressed. However, for semiconductors with a band gap larger than this window, as used in blue-emitting organic light-emitting diodes, the removal or disabling of charge traps poses a longstanding challenge. Here we demonstrate a molecular strategy where the highest occupied molecular orbital and lowest unoccupied molecular orbital are spatially separated on different parts of the molecules. By tuning their stacking by modification of the chemical structure, the lowest unoccupied molecular orbitals can be spatially protected from impurities that cause electron trapping, increasing the electron current by orders of magnitude. In this way, the trap-free window can be substantially broadened, opening a path towards large band gap organic semiconductors with balanced and trap-free transport.
Collapse
Affiliation(s)
- Oskar Sachnik
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Xiao Tan
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Dehai Dou
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | - Naomi Kinaret
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Kun-Han Lin
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | | | - Robert Graf
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany.
| |
Collapse
|
4
|
Li Y, Van der Zee B, Tan X, Zhou X, Wetzelaer GJAH, Blom PWM. Enhanced Operational Stability by Cavity Control of Single-Layer Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence. Adv Mater 2023:e2304728. [PMID: 37586746 DOI: 10.1002/adma.202304728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 08/11/2023] [Indexed: 08/18/2023]
Abstract
Highly efficient organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters are realized in recent years, but the device lifetime needs further improvement for practical display or lighting applications. In this work, a device design principle is presented by tuning the optical cavity of single-layer undoped devices, to realize efficient and long-lived TADF OLEDs. Extending the cavity length to the second-order interference maximum by increasing the emissive layer thickness broadens the recombination zone, while the optical outcoupling efficiency remains close to that of the thinner first-order devices. Such a device design leads to efficient and stable single-layer undoped OLEDs with a maximum external quantum efficiency of 16%, an LT90 of 452 h, and an LT50 of 3693 h at an initial luminance of 1000 cd m-2 , which is doubled compared to the first-order counterparts. It is further demonstrated that the widely-used empirical relation between OLED lifetime and light intensity originates from triplet-polaron annihilation, resulting in an extrapolated LT50 at 100 cd m-2 of close to 90 000 h, approaching the demands for practical backlight applications.
Collapse
Affiliation(s)
- Yungui Li
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Bas Van der Zee
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Xiao Tan
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Xin Zhou
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| |
Collapse
|
5
|
Wu Y, Li Y, van der Zee B, Liu W, Markina A, Fan H, Yang H, Cui C, Li Y, Blom PWM, Andrienko D, Wetzelaer GJAH. Reduced bimolecular charge recombination in efficient organic solar cells comprising non-fullerene acceptors. Sci Rep 2023; 13:4717. [PMID: 36949087 PMCID: PMC10033508 DOI: 10.1038/s41598-023-31929-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/20/2023] [Indexed: 03/24/2023] Open
Abstract
Bimolecular charge recombination is one of the most important loss processes in organic solar cells. However, the bimolecular recombination rate in solar cells based on novel non-fullerene acceptors is mostly unclear. Moreover, the origin of the reduced-Langevin recombination rate in bulk heterojunction solar cells in general is still poorly understood. Here, we investigate the bimolecular recombination rate and charge transport in a series of high-performance organic solar cells based on non-fullerene acceptors. From steady-state dark injection measurements and drift-diffusion simulations of the current-voltage characteristics under illumination, Langevin reduction factors of up to over two orders of magnitude are observed. The reduced recombination is essential for the high fill factors of these solar cells. The Langevin reduction factors are observed to correlate with the quadrupole moment of the acceptors, which is responsible for band bending at the donor-acceptor interface, forming a barrier for charge recombination. Overall these results therefore show that suppressed bimolecular recombination is essential for the performance of organic solar cells and provide design rules for novel materials.
Collapse
Affiliation(s)
- Yue Wu
- Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Yungui Li
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Bas van der Zee
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Wenlan Liu
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Anastasia Markina
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Hongyu Fan
- Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Hang Yang
- Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Chaohua Cui
- Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China.
| | - Yongfang Li
- Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China
| | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Denis Andrienko
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | | |
Collapse
|
6
|
Sachnik O, Li Y, Tan X, Michels JJ, Blom PWM, Wetzelaer GJAH. Single-Layer Blue Organic Light-Emitting Diodes With Near-Unity Internal Quantum Efficiency. Adv Mater 2023:e2300574. [PMID: 36914566 DOI: 10.1002/adma.202300574] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 03/09/2023] [Indexed: 05/09/2023]
Abstract
Efficient organic light-emitting diodes (OLEDs) commonly comprise a multilayer stack including charge-transport and charge- and exciton-blocking layers, to confine charge recombination to the emissive layer. Here, a highly simplified single-layer blue-emitting OLED is demonstrated based on thermally activated delayed fluorescence with the emitting layer simply sandwiched between ohmic contacts consisting of a polymeric conducting anode and a metal cathode. The single-layer OLED exhibits an external quantum efficiency of 27.7% with minor roll-off at high brightness. The internal quantum efficiency approaches unity, demonstrating that highly simplified single-layer OLEDs without confinement layers can achieve state-of-the-art performance, while greatly reducing the complexity of the design, fabrication, and device analysis.
Collapse
Affiliation(s)
- Oskar Sachnik
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Yungui Li
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Xiao Tan
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Jasper J Michels
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | | |
Collapse
|
7
|
Van der Zee B, Li Y, Wetzelaer GJAH, Blom PWM. Efficiency of Polymer Light-Emitting Diodes: A Perspective. Adv Mater 2022; 34:e2108887. [PMID: 34786784 DOI: 10.1002/adma.202108887] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Indexed: 06/13/2023]
Abstract
The various contributions to the external quantum efficiency (EQE) of polymer light-emitting diodes (PLEDs) are discussed. The EQE of an organic light-emitting diode is governed by a number of parameters, such as the electrical efficiency, the photoluminescence quantum yield (PLQY), the optical outcoupling efficiency and the spin statistics for singlet exciton generation. In the last decade, the electrical efficiency has been determined from a numerical PLED device model. More recently, an optical model to simulate the fraction of photons outcoupled to air for PLEDs with a broad recombination zone has been developed. Together with the directly measured PLQY, the EQE of a PLED can then be estimated. However, it has been observed that the measured EQEs of fluorescent PLEDs, including the model system super-yellow poly(p-phenylene vinylene) (SY-PPV) often exceed the expected values. To solve this discrepancy, it is demonstrate that the electrical PLED model has to be expanded by the inclusion of triplet-triplet annihilation (TTA), which is shown to be responsible for a substantial EQE enhancement. Experimentally, it is obtained that TTA contributes to a singlet-exciton generation efficiency of ≈40% in SY-PPV PLEDs, giving rise to an EQE of ≈4% instead of the expected value of 2.5%.
Collapse
Affiliation(s)
- Bas Van der Zee
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
| | - Yungui Li
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
| |
Collapse
|
8
|
Wetzelaer GJAH, Blom PWM. Comment on "Enhanced Charge Selectivity via Anodic-C 60 Layer Reduces Nonradiative Losses in Organic Solar Cells". ACS Appl Mater Interfaces 2022; 14:7523-7526. [PMID: 35112566 PMCID: PMC8855338 DOI: 10.1021/acsami.1c05333] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Understanding interface-related phenomena is important for improving the performance of thin-film solar cells. In ACS Appl. Mater. Interfaces 2021, 13, 12603-12609, Pranav et al. report that incorporating a thin C60 interlayer at the MoO3 anode results in reduced surface recombination of electrons, which is ascribed to a decreased electron accumulation near the anode on account of an increased built-in voltage. Here, we offer an alternative explanation: the introduction of a C60 interlayer renders the MoO3 contact Ohmic. The reduced anode barrier simultaneously increases the built-in voltage, minimizes nonradiative voltage losses upon the extraction of majority carriers (holes), and suppresses minority-carrier (electron) surface recombination, the latter being the result of hole accumulation and associated band bending near the Ohmic hole contact. We therefore argue that Ohmic contact formation suppresses both majority- and minority-carrier surface recombination losses, whereas the built-in voltage per se does not play a major role in this respect.
Collapse
|
9
|
Abstract
Thermally-activated delayed fluorescence (TADF) is a concept which helps to harvest triplet excitations, boosting the efficiency of an organic light-emitting diode. TADF can be observed in molecules with spatially separated donor and acceptor groups with a reduced triplet-singlet energy level splitting. TADF materials with balanced electron and hole transport are attractive for realizing efficient single-layer organic light emitting diodes, greatly simplifying their manufacturing and improving their stability. Our goal here is to computationally screen such materials and provide a comprehensive database of compounds with a range of emission wavelengths, ionization energies, and electron affinities.
Collapse
Affiliation(s)
- Kun-Han Lin
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | |
Collapse
|
10
|
Kaiser S, Kotadiya NB, Rohloff R, Fediai A, Symalla F, Neumann T, Wetzelaer GJAH, Blom PWM, Wenzel W. De Novo Simulation of Charge Transport through Organic Single-Carrier Devices. J Chem Theory Comput 2021; 17:6416-6422. [PMID: 34590481 DOI: 10.1021/acs.jctc.1c00584] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In amorphous organic semiconductor devices, electrons and holes are transported through layers of small organic molecules or polymers. The overall performance of the device depends both on the material and the device configuration. Measuring a single device configuration requires a large effort of synthesizing the molecules and fabricating the device, rendering the search for promising materials in the vast molecular space both nontrivial and time-consuming. This effort could be greatly reduced by computing the device characteristics from the first principles. Here, we compute transport characteristics of unipolar single-layer devices of prototypical hole- and electron-transporting materials, N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (α-NPD) and 2,2',2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) using a first-principles multiscale approach that requires only the molecular constituents and the device geometry. This approach of generating a digital twin of the entire device can be extended to multilayer stacks and enables the computer design of materials and devices to facilitate systematic improvement of organic light-emitting diode (OLED) devices.
Collapse
Affiliation(s)
- Simon Kaiser
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Naresh B Kotadiya
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Roland Rohloff
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Artem Fediai
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Franz Symalla
- Nanomatch GmbH, Griesbachstr. 5, 76185 Karlsruhe, Germany
| | - Tobias Neumann
- Nanomatch GmbH, Griesbachstr. 5, 76185 Karlsruhe, Germany
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Wolfgang Wenzel
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| |
Collapse
|
11
|
Sajedi Alvar M, Blom PWM, Wetzelaer GJAH. Space-charge-limited electron and hole currents in hybrid organic-inorganic perovskites. Nat Commun 2020; 11:4023. [PMID: 32782256 PMCID: PMC7419305 DOI: 10.1038/s41467-020-17868-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 07/21/2020] [Indexed: 11/29/2022] Open
Abstract
Hybrid organic-inorganic perovskites are promising materials for the application in solar cells and light-emitting diodes. However, the basic current-voltage behavior for electrons and holes is still poorly understood in these semiconductors due to their mixed electronic-ionic character. Here, we present the analysis of space-charge-limited electron and hole currents in the archetypical perovskite methyl ammonium lead iodide (MAPbI3). We demonstrate that the frequency dependence of the permittivity plays a crucial role in the analysis of space-charge-limited currents and their dependence on voltage scan rate and temperature. Using a mixed electronic-ionic device model based on experimentally determined parameters, the current-voltage characteristics of single-carrier devices are accurately reproduced. Our results reveal that in our solution processed MAPbI3 thin films transport of electrons dominates over holes. Furthermore, we show that the direction of the hysteresis in the current-voltage characteristics provides a fingerprint for the sign of the dominant moving ionic species.
Collapse
Affiliation(s)
| | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | | |
Collapse
|
12
|
Kotadiya NB, Mondal A, Blom PWM, Andrienko D, Wetzelaer GJAH. A window to trap-free charge transport in organic semiconducting thin films. Nat Mater 2019; 18:1182-1186. [PMID: 31548633 DOI: 10.1038/s41563-019-0473-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/31/2019] [Indexed: 06/10/2023]
Abstract
Organic semiconductors, which serve as the active component in devices, such as solar cells, light-emitting diodes and field-effect transistors1, often exhibit highly unipolar charge transport, meaning that they predominantly conduct either electrons or holes. Here, we identify an energy window inside which organic semiconductors do not experience charge trapping for device-relevant thicknesses in the range of 100 to 300 nm, leading to trap-free charge transport of both carriers. When the ionization energy of a material surpasses 6 eV, hole trapping will limit the hole transport, whereas an electron affinity lower than 3.6 eV will give rise to trap-limited electron transport. When both energy levels are within this window, trap-free bipolar charge transport occurs. Based on simulations, water clusters are proposed to be the source of hole trapping. Organic semiconductors with energy levels situated within this energy window may lead to optoelectronic devices with enhanced performance. However, for blue-emitting light-emitting diodes, which require an energy gap of 3 eV, removing or disabling charge traps will remain a challenge.
Collapse
Affiliation(s)
| | - Anirban Mondal
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | | |
Collapse
|
13
|
Kotadiya NB, Lu H, Mondal A, Ie Y, Andrienko D, Blom PWM, Wetzelaer GJAH. Publisher Correction: Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies. Nat Mater 2018; 17:563. [PMID: 29511322 DOI: 10.1038/s41563-018-0043-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the html version of this Article originally published, Paul W. M. Blom and Gert-Jan A. H. Wetzelaer were incorrectly listed as Paul M. W. Blom and Gert-Jan H. A. Wetzelaer, respectively, due to a technical error. This has now been amended in all online versions of the Article.
Collapse
Affiliation(s)
| | - Hao Lu
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Anirban Mondal
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Yutaka Ie
- Max Planck Institute for Polymer Research, Mainz, Germany
- The Institute of Scientific and Industrial Research (ISIR), Osaka University, Ibaraki, Japan
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | |
Collapse
|
14
|
Niu Q, Rohloff R, Wetzelaer GJAH, Blom PWM, Crăciun NI. Hole trap formation in polymer light-emitting diodes under current stress. Nat Mater 2018; 17:557-562. [PMID: 29662159 DOI: 10.1038/s41563-018-0057-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 03/13/2018] [Indexed: 06/08/2023]
Abstract
Polymer light-emitting diodes (PLEDs) are attractive for use in large-area displays and lighting panels, but their limited stability under current stress impedes commercialization. In spite of large efforts over the last two decades a fundamental understanding of the degradation mechanisms has not been accomplished. Here we demonstrate that the voltage drift of a PLED driven at constant current is caused by the formation of hole traps, which leads to additional non-radiative recombination between free electrons and trapped holes. The observed trap formation rate is consistent with exciton-free hole interactions as the main mechanism behind PLED degradation, enabling us to unify the degradation behaviour of various poly(p-phenylene) derivatives. The knowledge that hole trap formation is the cause of PLED degradation means that we can suppress the negative effect of hole traps on voltage and efficiency by blending the light-emitting polymer with a large-bandgap semiconductor. Owing to trap-dilution these blended PLEDs show unprecedented stability.
Collapse
Affiliation(s)
- Quan Niu
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Roland Rohloff
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | |
Collapse
|
15
|
Kotadiya NB, Lu H, Mondal A, Ie Y, Andrienko D, Blom PWM, Wetzelaer GJAH. Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies. Nat Mater 2018; 17:329-334. [PMID: 29459747 DOI: 10.1038/s41563-018-0022-8] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 01/15/2018] [Indexed: 06/08/2023]
Abstract
Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor. Insertion of the interlayer results in electrostatic decoupling of the electrode from the semiconductor and realignment of the Fermi level with the IE of the organic semiconductor. The Ohmic-contact formation is illustrated for a number of material combinations and solves the problem of hole injection into organic semiconductors with a high IE of up to 6 eV.
Collapse
Affiliation(s)
| | - Hao Lu
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Anirban Mondal
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Yutaka Ie
- Max Planck Institute for Polymer Research, Mainz, Germany
- The Institute of Scientific and Industrial Research (ISIR), Osaka University, Ibaraki, Japan
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Mainz, Germany
| | | |
Collapse
|
16
|
Niu Q, Crăciun NI, Wetzelaer GJAH, Blom PWM. Origin of Negative Capacitance in Bipolar Organic Diodes. Phys Rev Lett 2018; 120:116602. [PMID: 29601741 DOI: 10.1103/physrevlett.120.116602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Indexed: 06/08/2023]
Abstract
Negative differential capacitance (NC) occurring at low frequencies in organic light-emitting diodes (OLEDs) is a poorly understood phenomenon. We study the origin of the NC effect by systematically varying the number of electron traps in OLEDs based on the polymeric semiconductor poly(p-phenylene vinylene). Increasing the electron trap density enhances the NC effect. The magnitude and observed decrease of the relaxation time is consistent with the (inverse) rate of trap-assisted recombination. The absence of NC in a nearly trap-free light-emitting diode unambiguously shows that trap-assisted recombination is the responsible mechanism for the negative contribution to the capacitance in bipolar organic diodes. Our results reveal that the NC effect can be exploited to quantitatively determine the number of traps in organic semiconductors in a nondestructive fashion.
Collapse
Affiliation(s)
- Quan Niu
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - N Irina Crăciun
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | | | - Paul W M Blom
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| |
Collapse
|
17
|
Skrypnychuk V, Wetzelaer GJAH, Gordiichuk PI, Mannsfeld SCB, Herrmann A, Toney MF, Barbero DR. Ultrahigh Mobility in an Organic Semiconductor by Vertical Chain Alignment. Adv Mater 2016; 28:2359-2366. [PMID: 26813586 DOI: 10.1002/adma.201503422] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 11/04/2015] [Indexed: 06/05/2023]
Abstract
A method to produce highly efficient and long-range vertical charge transport is demonstrated in an undoped polythiophene thin film, with average mobilities above 3.1 cm(2) V(-1) s(-1) . These record high mobilities are achieved by controlled orientation of the polymer crystallites enabling the most efficient and fastest charge transport along the chain backbones and across multiple chains. The significant increase in mobility shown here may present a new route to producing faster and more efficient optoelectronic devices based on organic materials.
Collapse
Affiliation(s)
- Vasyl Skrypnychuk
- Nano-Engineered Materials & Organic Electronics Laboratory, Umeå University, Umeå, 90187, Sweden
| | - Gert-Jan A H Wetzelaer
- Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Pavlo I Gordiichuk
- Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Stefan C B Mannsfeld
- Materials Science Division, Stanford Synchrotron Radiation Lightsource, Menlo Park, CA, 94025, USA
| | - Andreas Herrmann
- Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Michael F Toney
- Materials Science Division, Stanford Synchrotron Radiation Lightsource, Menlo Park, CA, 94025, USA
| | - David R Barbero
- Nano-Engineered Materials & Organic Electronics Laboratory, Umeå University, Umeå, 90187, Sweden
| |
Collapse
|
18
|
Gordiichuk PI, Rimmerman D, Paul A, Gautier DA, Gruszka A, Saller M, de Vries JW, Wetzelaer GJAH, Manca M, Gomulya W, Matmor M, Gloukhikh E, Loznik M, Ashkenasy N, Blom PWM, Rögner M, Loi MA, Richter S, Herrmann A. Filling the Green Gap of a Megadalton Photosystem I Complex by Conjugation of Organic Dyes. Bioconjug Chem 2015; 27:36-41. [DOI: 10.1021/acs.bioconjchem.5b00583] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Dolev Rimmerman
- The
Bio and Molecular Electronics Group, Department of Materials Science
and Engineering, Faculty of Engineering and University Center for
Nano Science and Nanotechnology, Tel Aviv University, Tel-Aviv, 69978, Israel
| | | | | | | | | | | | | | | | | | - Maayan Matmor
- Department
of Materials Engineering and the Ilze Katz Institute for Nanoscale
Science and Technology, Ben Gurion University of the Negev, Beer-Sheva, Israel
| | - Ekaterina Gloukhikh
- The
Bio and Molecular Electronics Group, Department of Materials Science
and Engineering, Faculty of Engineering and University Center for
Nano Science and Nanotechnology, Tel Aviv University, Tel-Aviv, 69978, Israel
| | | | - Nurit Ashkenasy
- Department
of Materials Engineering and the Ilze Katz Institute for Nanoscale
Science and Technology, Ben Gurion University of the Negev, Beer-Sheva, Israel
| | - Paul W. M. Blom
- Molecular
Electronics Group, Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Matthias Rögner
- Plant Biochemistry, Ruhr University Bochum, D-44780 Bochum, Germany
| | | | - Shachar Richter
- The
Bio and Molecular Electronics Group, Department of Materials Science
and Engineering, Faculty of Engineering and University Center for
Nano Science and Nanotechnology, Tel Aviv University, Tel-Aviv, 69978, Israel
| | | |
Collapse
|
19
|
Wetzelaer GJAH, Scheepers M, Sempere AM, Momblona C, Ávila J, Bolink HJ. Trap-assisted non-radiative recombination in organic-inorganic perovskite solar cells. Adv Mater 2015; 27:1837-1841. [PMID: 25648930 DOI: 10.1002/adma.201405372] [Citation(s) in RCA: 217] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 12/23/2014] [Indexed: 05/28/2023]
Affiliation(s)
- Gert-Jan A H Wetzelaer
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | | | | | | | | | | |
Collapse
|
20
|
Gordiichuk PI, Wetzelaer GJAH, Rimmerman D, Gruszka A, de Vries JW, Saller M, Gautier DA, Catarci S, Pesce D, Richter S, Blom PWM, Herrmann A. Solid-state biophotovoltaic cells containing photosystem I. Adv Mater 2014; 26:4863-9. [PMID: 24862686 DOI: 10.1002/adma.201401135] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 04/17/2014] [Indexed: 05/20/2023]
Abstract
The large multiprotein complex, photosystem I (PSI), which is at the heart of light-dependent reactions in photosynthesis, is integrated as the active component in a solid-state organic photovoltaic cell. These experiments demonstrate that photoactive megadalton protein complexes are compatible with solution processing of organic-semiconductor materials and operate in a dry non-natural environment that is very different from the biological membrane.
Collapse
Affiliation(s)
- Pavlo I Gordiichuk
- Polymer Chemistry and Bioengineering Group, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Kuik M, Wetzelaer GJAH, Nicolai HT, Craciun NI, De Leeuw DM, Blom PWM. 25th anniversary article: charge transport and recombination in polymer light-emitting diodes. Adv Mater 2014; 26:512-531. [PMID: 24458577 DOI: 10.1002/adma.201303393] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/18/2013] [Indexed: 06/03/2023]
Abstract
This article reviews the basic physical processes of charge transport and recombination in organic semiconductors. As a workhorse, LEDs based on a single layer of poly(p-phenylene vinylene) (PPV) derivatives are used. The hole transport in these PPV derivatives is governed by trap-free space-charge-limited conduction, with the mobility depending on the electric field and charge-carrier density. These dependencies are generally described in the framework of hopping transport in a Gaussian density of states distribution. The electron transport on the other hand is orders of magnitude lower than the hole transport. The reason is that electron transport is hindered by the presence of a universal electron trap, located at 3.6 eV below vacuum with a typical density of ca. 3 × 10¹⁷ cm⁻³. The trapped electrons recombine with free holes via a non-radiative trap-assisted recombination process, which is a competing loss process with respect to the emissive bimolecular Langevin recombination. The trap-assisted recombination in disordered organic semiconductors is governed by the diffusion of the free carrier (hole) towards the trapped carrier (electron), similar to the Langevin recombination of free carriers where both carriers are mobile. As a result, with the charge-carrier mobilities and amount of trapping centers known from charge-transport measurements, the radiative recombination as well as loss processes in disordered organic semiconductors can be fully predicted. Evidently, future work should focus on the identification and removing of electron traps. This will not only eliminate the non-radiative trap-assisted recombination, but, in addition, will shift the recombination zone towards the center of the device, leading to an efficiency improvement of more than a factor of two in single-layer polymer LEDs.
Collapse
Affiliation(s)
- Martijn Kuik
- Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | | | | | | | | | | |
Collapse
|
22
|
Bouwer RKM, Wetzelaer GJAH, Blom PWM, Hummelen JC. Influence of the isomeric composition of the acceptor on the performance of organic bulk heterojunction P3HT:bis-PCBM solar cells. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm32993j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
23
|
Lu M, Nicolai HT, Wetzelaer GJAH, Blom PWM. Effect of n-type doping on the hole transport in poly(p-phenylene vinylene). ACTA ACUST UNITED AC 2011. [DOI: 10.1002/polb.22372] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|