Fluoro- and Amino-Functionalized Conjugated Polymers as Electron Transport Materials for Perovskite Solar Cells with Improved Efficiency and Stability

Non-Fullerene Organic Electron Transport Materials toward Stable and Efficient Inverted Perovskite Photovoltaics

Inverted perovskite solar cells (PSCs) attract continuing interest due to their low processing temperature, suppressed hysteresis, and compatibility with tandem cells. Considerable progress has been made with reported power conversion efficiency (PCE) surpassing 26%. Electron transport Materials (ETMs) play a critical role in achieving high-performance PSCs because they not only govern electron extraction and transport from the perovskite layer to the cathode, but also protect the perovskite from contact with ambient environment. On the other hand, the non-radiative recombination losses at the perovskite/ETM interface also limits the future development of PSCs. Compared with fullerene derivatives, non-fullerene n-type organic semiconductors feature advantages like molecular structure diversity, adjustable energy level, and easy modification. Herein, the non-fullerene ETM is systematically summarized based on the molecular functionalization strategy. Various types of molecular design approaches for producing non-fullerene ETM are presented, and the insight on relationship of chemical structure and device performance is discussed. Meantime, the future trend of non-fullerene ETM is analyzed. It is hoped that this review provides insightful perspective for the innovation of new non-fullerene ETMs toward more efficient and stable PSCs.

Potassium stearate doped PEDOT:PSS improves the performance of inverted perovskite solar cells

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) suffers from lower conductivity and surface defects, which hinders the extraction and transport of effective charges, thereby reducing the Power conversion efficiency (PCE) and long-term stability of PSCs. Therefore, this study introduces potassium stearate (KSt) doping in PEDOT:PSS to regulate its conductivity and interface charge transfer. As a result, KSt-doped PEDOT:PSS increase the PCE of the device from 16.35% to 18.35%. Moreover, the PCE of PSCs with KSt-doped PEDOT:PSS can maintain 87% of its initial value after being stored in a glove box for over 700 hours. This work provides a simple and effective method for designing high-performance and stable PSCs.

Application of conjugated materials in sports training

In recent years, with the rapid development of the sports industry, the quality of sports training products on the market is uneven. Problems such as inaccurate detection of athletes' physical indicators, low comfort of sportswear, and reduced satisfaction with sports equipment often occur. To this end, this article proposes to apply conjugated materials with excellent optical, electrical, thermal and other properties to sports training and sports products, by summarizing the properties of conjugated materials and their applications in sports training, explores the potential of conjugated materials in improving athletes' training effects, monitoring sports status, and improving sports equipment. This article rates the application of conjugated materials in sports training products in terms of comfort, waterproofness, portability, lightness, aesthetics and breathability. The results showed that the average scores of the 20 sports participants on sportswear were 9.0475, 9.0075, 9.01, 9.025, 9.0325 and 9.04 respectively; the average scores on sports shoes were 9.035, 9.055, 9.02, 9.085, 9.0175 and 8.9975 respectively. Research shows that applying conjugated materials to sports training can improve athletes' performance and contribute to the better development of sports.

First-Principles Insights into Structural, Optoelectronic, and Elastic Properties of Fluoro-Perovskites KXF3 (X = Ru, Os)

The need for new and better semiconductor materials for use in renewable energy devices motivates us to study KRuF3 and KOsF3 fluoride materials. In the present work, we computationally studied these materials and elaborate their varied properties comprehensively with the assistance of density functional theory-based techniques. To find the structural stability of these under-consideration materials, we employed the Birch-Murnaghan fit, while their electronic characteristics were determined with the usage of modified potential of Becke-Johnson. During the study, it became evident from the band-structure results of the KRuF3 and KOsF3 materials that both present an indirect semiconductor nature having the band gap values of 2.1 and 1.7 eV, respectively. For both the studied materials, the three essential elastic constants were determined first, which were further used to evaluate all the mechanical parameters of the studied materials. From the calculated values of Pugh's ratio and Poisson's ratio for the KRuF3 and KOsF3 materials, both were verified to procure the nature of ductility. During the study, we concluded from the results of absorption coefficient and optical conduction in the UV energy range that both the studied materials proved their ability for utilization in the numerous future optoelectronic devices.

Detail computational study about the structural, electronic, optical, and mechanical properties of RbVX3 (Cl, Br, I) halide perovskite materials

The non-toxic nature of lead-free materials with cubic perovskite structure has attracted the researcher's attention, and huge work is ongoing for the search of such materials. Furthermore, due to demand for their utilization in diverse applications, such as photovoltaic and optoelectronics, these inorganic-halide materials have become more enchanting for engineers. In the present work, all the key properties, including structural, electronic, optical, and mechanical, of rubidium based RbVX₃ (where X is chlorine, bromine, and iodine) materials were extensively studied via first-principle density functional theory (DFT). The study reveals the half-metallic nature of the currently studied materials. For the mechanical stability of RbVX₃ compounds, all three independent elastic coefficients (C_ij) were determined, from which it was concluded that these materials are mechanically stable. Moreover, from the Poison and Pugh's ratios, it was found that the RbVCl₃ and RbVBr₃ materials have ductile nature, while RbVI₃ has brittle nature upon the applied stress.

Structural, Electronic and Optical Properties of Titanium Based Fluoro-Perovskites MTiF3 (M = Rb and Cs) via Density Functional Theory Computation

This study reports the theoretical investigations on the structural, electronic, and optical properties of titanium-based fluoro-perovskites MTiF₃ (M = Cs and Rb) using density functional theory. The impact of on-site Coulomb interactions is considered, and calculations are performed in generalized gradient approximation with the Hubbard U term (GGA + U). The ground state parameters, such as lattice constants, bulk modulus, and pressure derivatives of bulk modulus, were found. These compounds are found stable in cubic perovskite structures having lattice constants of 4.30 and 4.38 Å for RbTiF₃ and CsTiF₃, respectively. Analysis of elastic properties shows that both of the compounds are ductile in nature. According to the band structure profile, the examined compounds have a half-metallic character, exhibiting conducting behavior in the spin-up configuration and nonconducting behavior in the spin-down configuration. The ferromagnetic nature is conformed from the study of its magnetic moments. The optical behaviors such as reflectivity, absorption, refraction, and conductivity of the cubic phase of MTiF₃ (M = Rb and Cs) are studied in the energy range of 0-40 eV.

Insight into the Structural, Electronic, Elastic, Optical, and Magnetic Properties of Cubic Fluoroperovskites ABF3 (A = Tl, B = Nb, V) Compounds: Probed by DFT

This work displays the structural, electronic, elastic, optical, and magnetic properties in spin-polarized configurations for cubic fluoroperovskite ABF3 (A = Tl, B = Nb, V) compounds studied by density functional theory (DFT) by means of the Tran-Blaha-modified Becke-Johnson (TB-mBJ) approach. The ground state characteristics of these compounds, i.e., the lattice parameters a0, bulk modulus (B), and its pressure derivative B' are investigated. The structural properties depict that the selected compounds retain a cubic crystalline structure and have stable ground state energy. Electronic-band structures and DOS (density of states) in spin-polarized cases are studied which reports the semiconducting nature of both materials. The TDOS (total density of states) and PDOS (partial density of states) studies in both spin configurations show that the maximum contributions of states to the different bands is due to the B-site (p-states) atoms as well as F (p-states) atoms. Elastic properties including anisotropy factor (A), elastic constants, i.e., C₁₁, C₁₂, and C₄₄, Poisson's ratio (υ), shear modulus and (G), Young's modulus (E) are computed. In terms of elastic properties, the higher (bulk modulus) "B" and ratio of "B/G" yield that these materials exhibit a ductile character. Magnetic properties indicate that both the compounds are ferromagnetic. In addition, investigations of the optical spectra including the real (ε1ω) and imaginary (ε2ω) component of the dielectric function, refractive index nω, optical reflectivity Rω, optical conductivity σω, absorption coefficient αω, energy loss function Lω, and electron extinction coefficient kω are carried out which shows the transparent nature of TlVF3 and TlNbF3. Based on the reported research work on these selected materials, their applications can be predicted in many modern electronic gadgets.

Polymers in High-Efficiency Solar Cells: The Latest Reports

Third-generation solar cells, including dye-sensitized solar cells, bulk-heterojunction solar cells, and perovskite solar cells, are being intensively researched to obtain high efficiencies in converting solar energy into electricity. However, it is also important to note their stability over time and the devices' thermal or operating temperature range. Today's widely used polymeric materials are also used at various stages of the preparation of the complete device-it is worth mentioning that in dye-sensitized solar cells, suitable polymers can be used as flexible substrates counter-electrodes, gel electrolytes, and even dyes. In the case of bulk-heterojunction solar cells, they are used primarily as donor materials; however, there are reports in the literature of their use as acceptors. In perovskite devices, they are used as additives to improve the morphology of the perovskite, mainly as hole transport materials and also as additives to electron transport layers. Polymers, thanks to their numerous advantages, such as the possibility of practically any modification of their chemical structure and thus their physical and chemical properties, are increasingly used in devices that convert solar radiation into electrical energy, which is presented in this paper.

Enhanced Thermal Stability of Planar Perovskite Solar Cells Through Triphenylphosphine Interface Passivation

While extensive research has driven the rapid efficiency trajectory noted to date for organic-inorganic perovskite solar cells (PSCs), their thermal stability remains one of the key issues hindering their commercialization. Herein, a significant reduction in surface defects (a precursor to perovskite instability) could be attained by introducing triphenylphosphine (TPP), an effective Lewis base passivator, to the vulnerable perovskite/spiro-OMeTAD interface. Not only did TPP passivation enable a high power conversion efficiency (PCE) of 20.22 % to be achieved, these devices also exhibited superior ambient and thermal stability. Unlike the pristine device, which exhibited a sharp descend to 16 % of its initial PCE on storing in relative humidity of 10 %, at 85 °C for more than 720 h, the TPP-passivated devices retained 71 % of its initial PCE. Hence, this study presents a facile yet excellent approach to attain high-performing yet thermally stable PSCs.

Increasing Stability of SnO2-Based Perovskite Solar Cells by Introducing an Anionic Conjugated Polyelectrolyte for Interfacial Adjustment

Despite the fact that power conversion efficiency (PCE) has been greatly improved in recent years, perovskite solar cells (PSCs) need to overcome some challenges, like stability, for the commercial application. Herein, an anionic conjugated polyelectrolyte, sulfonic-containing polyfluorene (abbreviated to SPF), has been developed to modify the interface between the electron-transporting layer (ETL) SnO₂ and the optoelectronic active layer MAPbI₃ in the n-i-p cells. After 40 days of storage in atmospheric environment in the dark with exposure to a controlled humidity of about 10%, PCE of the SPF-modified cells with the structure of ITO/SnO₂/SPF/MAPbI₃/spiro-OMeTAD/Au still remained 94% of the initial value. In contrast, the control cell without SPF only remained 31.1% of its initial efficiency after 29 days. The main reason for the stability enhancement is the adjustment of interfacial energy level, the crystallinity enhancement, and the removal of the interfacial defect of the perovskite layer by introducing the hydrophobic and smooth SPF interfacial layer. Deep electrical study on the PSCs discloses that the cell has low carrier transfer resistance, low leakage current density, and minor interfacial charge accumulation. What's more, the short-circuit current density is improved, and PCE of 20.47% is achieved.

Long-range donor-acceptor electron transport mediated by α helices

We study the long-range electron and energy transfer mediated by a polaron on an α-helix polypeptide chain coupled to donor and acceptor molecules at opposite ends of the chain. We show that for specific parameters of the system, an electron initially located on the donor can tunnel onto the α helix, forming a polaron, which then travels to the other extremity of the polypeptide chain, where it is captured by the acceptor. We consider three families of couplings between the donor, the acceptor, and the chain and show that one of them can lead to a 90% efficiency of the electron transport from donor to acceptor. We also show that this process remains stable at physiological temperatures in the presence of thermal fluctuations in the system.

Existence of Ligands within Sol-Gel-Derived ZnO Films and Their Effect on Perovskite Solar Cells

The sol-gel (SG) method has been well-documented as one useful way to produce ZnO films as an excellent electron transport material (ETM) for efficient perovskite solar cells (PSCs). Generally, the precursor films containing zinc acetate dihydrate and a stabilizing ligand monoethanolamine (EA) were annealed to obtain ZnO films. A noteworthy issue is the commonly reported annealing temperature (T_a) in a wide range of 150-600 °C. In this work, we investigated the effect of the annealing temperature on the film composition and first confirmed the co-existence of acetate and EA species when T_a is below 380 °C. EA still survived within the ZnO films when T_a was between 380 and 450 °C. When T_a was over 450 °C, pure ZnO films can be obtained. The presence of ligands also remarkably altered the work function of the corresponding ZnO samples, thereby resulting in the remarkably different effects on the efficiency and stability of PSCs with the ZnO samples as ETMs. This work affords a clearer understanding of ZnO films prepared by the SG method at molecular insights, promoting their application in photoelectric fields.