Enhanced optical absorption via cation doping hybrid lead iodine perovskites

Solar-Powered AEM Electrolyzer via PGM-Free (Oxy)hydroxide Anode with Solar to Hydrogen Conversion Efficiency of 12.44

Water electrolyzers powered by renewable energy are emerging as clean and sustainable technology for producing hydrogen without carbon emissions. Specifically, anion exchange membrane (AEM) electrolyzers utilizing non-platinum group metal (non-PGM) catalysts have garnered attention as a cost-effective method for hydrogen production, especially when integrated with solar cells. Nonetheless, the progress of such integrated systems is hindered by inadequate water electrolysis efficiency, primarily caused by poor oxygen evolution reaction (OER) electrodes. To address this issue, a NiFeCo─OOH has developed as an OER electrocatalyst and successfully demonstrated its efficacy in an AEM electrolyzer, which is powered by renewable electricity and integrated with a silicon solar cell.

Structural Properties of Some Vacancy-Ordered Platinum Halide Perovskites

The structural changes that accompany the dehydration of Na2PtX6·6H2O (X = Cl, Br) were studied using in situ variable temperature synchrotron X-ray diffraction. The two hexahydrates are isostructural, containing isolated PtX6 octahedra separated by Na cations. Removal of the water results in the formation of the anhydrous vacancy ordered double perovskites Na2PtX6. The Na cation is too small for the cuboctahedron site of the parent cubic structure, resulting in cooperative tilting of the PtX6 octahedra and lowering of the symmetry. Replacing Na with a larger alkali metal (K, Rb, or Cs) invariably enabled the isolation of the anhydrous hexahalide, and we found no evidence that these readily hydrated. For all cations, other than Na, it was possible to observe the archetypical cubic structure, although for the two potassium salts K2PtBr6 and K2PtI6, this was only observed above a critical temperature of 175 and 460 K, respectively. As these two samples were cooled, symmetry lowering was observed, yielding a tetragonal structure initially and ultimately a monoclinic structure: Fm3̅m → P4/mnc → P21/n. These phase transitions are associated with the onset of long-range cooperative tilting of the PtX6 octahedra described using the Glazer tilt notation as a0a0a0 → a0a0c+ → a-a-c+.

High brightness and low operating voltage CsPbBr3 perovskite LEDs by single-source vapor deposition

In this work, we utilized CsPbBr3 powder as the precursor material for the single-source vapor deposition (SSVD) process to fabricate the CsPbBr3 emitting layer. Due to the high density of grain boundaries and defects in the thin films deposited in the initial stages, non-radiative recombination can occur, reducing the efficiency of perovskite light-emitting diodes (PeLED). To address this issue, we employed a thermal annealing process by subjecting the perovskite films to the appropriate annealing temperature, facilitating the coalescence and growth of different grains, improving lattice integrity, and thereby reducing the presence of defects and enhancing the photoluminescence performance of the films. Furthermore, in this study, we successfully fabricated simple-structured CsPbBr3 PeLED using thermally annealed CsPbBr3 films. Among these components, even without adding the electron and hole transport layers, the best-performing device achieved a maximum brightness of 14,079 cd/m2 at a driving voltage of only 2.92 V after annealing at 350 °C; the brightness is 16.8 times higher than that of CsPbBr3 PeLED without heat treatment, demonstrating outstanding light-emitting performance. The research results show that using SSVD to prepare CsPbBr3 PeLED has broad application potential, providing a simple process option for research on improving the performance of PeLED.

Insight into the interface engineering between methylammonium lead halide perovskites and gallium oxide: a first-principles approach

Interface engineering of the organo-lead halide perovskite devices has shown the potential to improve their efficiency and stability. In this study, the atomic, electronic, optical and transport characteristics of MAPbI3/Ga2O3 and MAPbCl3/Ga2O3 interfaces were investigated by using first-principles calculations. Eight different interfacial models were established and the interfacial properties were discussed. The results show that the PbI/O configuration exhibits the largest bonding strength out of all eight interfacial configurations. Owing to the larger interfacial interaction, the charge transfer at the PbI/O interface is significantly more than that at the other interfaces. The analysis of absorption spectra indicates that the Ga-terminated perovskite/Ga2O3 heterostructures are expected to have great potential for efficient optoelectronic applications. The analysis of transmission spectra shows that the MA/O configurations with more transmission peaks near the Fermi level exhibit lower resistance compared to others. The results of our study could help understand the interfacial engineering mechanism between perovskite and Ga2O3.

Morphological investigation and 3D simulation of plasmonic nanostructures to improve the efficiency of perovskite solar cells

The light absorption process is a key factor in improving the performance of perovskite solar cells (PSCs). Using arrays of metal nanostructures on semiconductors such as perovskite (CH3NH3PbI3), the amount of light absorption in these layers is significantly increased. Metal nanostructures have been considered for their ability to excite plasmons (collective oscillations of free electrons). Noble metal nanoparticles placed inside solar cells, by increasing the scattering of the incident light, effectively increase the optical absorption inside PSCs; this in turn increases the electric current generated in the photovoltaic device. In this work, by calculating the cross-sectional area of dispersion and absorption on gold (Au) nanoparticles, the effects of the position of nanoparticles in the active layer (AL) and their morphology on the increase of absorption within the PSC are investigated. The optimal position of the plasmonic nanoparticle was obtained in the middle of the AL using a three-dimensional simulation method. Then, three different morphologies of nano-sphere, nano-star and nano-cubes were investigated, where the short-circuit currents (Jsc) for these three nanostructures were obtained equal to 19.01, 18.66 and 20.03 mA/cm2, respectively. In our study, the best morphology of the nanostructure according to the Jsc value was related to the nano-cube, in which the device power conversion efficiency was equal to 16.20%, which is about 15% better than the PSC with the planar architecture.

Design of optimized photonic-structure and analysis of adding a SiO2 layer on the parallel CH3NH3PbI3/CH3NH3SnI3 perovskite solar cells

So far, remarkable achievements have been obtained by optimizing the device architecture and modeling of solar cells is a precious and very effective way to comprehend a better description of the physical mechanisms in solar cells. As a result, this study has inspected two-dimensional simulation of perovskite solar cells (PSCs) to achieve a precise model. The solution which has been employed is based on the finite element method (FEM). First, the periodically light trapping (LT) structure has been replaced with a planar structure. Due to that, the power conversion efficiency (PCE) of PSC was obtained at 14.85%. Then, the effect of adding an SiO2 layer to the LT structure as an anti-reflector layer was investigated. Moreover, increasing the PCE of these types of solar cells, a new structure including a layer of CH3NH3SnI3 as an absorber layer was added to the structure of PSCs in this study, which resulted in 25.63 mA/cm2 short circuit current (Jsc), 0.96 V open circuit voltage (Voc), and 20.48% PCE.

CsPbBr3 and Cs4PbBr6 perovskite light-emitting diodes using a thermally evaporated host-dopant system

This article shows the results of fabricating a device through vacuum deposition by synthesizing a perovskite thin film in the powder form. Light emitting diodes (LEDs) were fabricated using a single-source and host-dopant system of the perovskite produced in the powder form. Both CsPbBr₃ and Cs₄PbBr₆ used in the host-dopant system were green, and the host was tris(8-quinolinolato) aluminum(III). It is confirmed that the display efficiency and optical characteristics are significantly improved by the dopant ratio. The 3%-doped CsPbBr₃ based LED shows a luminance of 9083 cd m^-2, 3.36% external quantum efficiency (EQE), and 96% photoluminescence quantum yield (PLQY) efficiency (for the undoped CsPbBr₃ LED, luminance: 844 cd m^-2/EQE: 1.93%/PLQY: 85%). The LED based on 5%-doped Cs₄PbBr₆ shows a luminance of 11 440 cd m^-2, an EQE of 6.27%, and 99% PLQY efficiency (for the undoped Cs₄PbBr₆ LED, luminance:1113 cd m^-2/EQE: 1.64%/PLQY: 93%). It is expected that the results of this research will contribute to the perovskite LED research performed by thermal evaporation in the future.

Effect of aliovalent bismuth substitution on structure and optical properties of CsSnBr3

Aliovalent substitution of the B component in ABX₃ metal halides has often been proposed to modify the band gap and thus the photovoltaic properties, but details about the resulting structure have remained largely unknown. Here, we examine these effects in Bi-substituted CsSnBr₃. Powder X-ray diffraction (XRD) and solid-state ¹¹⁹Sn, ¹³³Cs and ²⁰⁹Bi nuclear magnetic resonance (NMR) spectroscopy were carried out to infer how Bi substitution changes the structure of these compounds. The cubic perovskite structure is preserved upon Bi-substitution, but with disorder in the B site occurring at the atomic level. Bi atoms are randomly distributed as they substitute for Sn atoms with no evidence of Bi segregation. The absorption edge in the optical spectra shifts from 1.8 to 1.2 eV upon Bi-substitution, maintaining a direct band gap according to electronic structure calculations. It is shown that Bi-substitution improves resistance to degradation by inhibiting the oxidation of Sn.

Bi and Sn Doping Improved the Structural, Optical and Photovoltaic Properties of MAPbI3-Based Perovskite Solar Cells

One of the most amazing photovoltaic technologies for the future is the organic–inorganic lead halide perovskite solar cell, which exhibits excellent power conversion efficiency (PCE) and can be produced using a straightforward solution technique. Toxic lead in perovskite can be replaced by non-toxic alkaline earth metal cations because they keep the charge balance in the material and some of them match the Goldschmidt rule’s tolerance factor. Therefore, thin films of MAPbI₃, 1% Bi and 0%, 0.5%, 1% and 1.5% Sn co-doped MAPbI₃ were deposited on FTO-glass substrates by sol-gel spin-coating technique. XRD confirmed the co-doping of Bi–Sn in MAPbI₃. The 1% Bi and 1% Sn co-doped film had a large grain size. The optical properties were calculated by UV-Vis spectroscopy. The 1% Bi and 1% Sn co-doped film had small E_g, which make it a good material for perovskite solar cells. These films were made into perovskite solar cells. The pure MAPbI₃ film-based solar cell had a current density (J_sc) of 9.71 MA-cm⁻², its open-circuit voltage (V_oc) was 1.18 V, its fill factor (FF) was 0.609 and its efficiency (η) was 6.98%. All of these parameters were improved by the co-doping of Bi–Sn. The cell made from a co-doped MAPbI₃ film with 1% Bi and 1% Sn had a high efficiency (10.03%).

Halide Perovskite Solar Cells for Building Integrated Photovoltaics: Transforming Building Façades into Power Generators

The rapid emergence of organic-inorganic lead halide perovskites for low-cost and high-efficiency photovoltaics promises to impact new photovoltaic concepts. Their high power conversion efficiencies, ability to coat perovskite layers on glass via various scalable deposition techniques, excellent optoelectronic properties, and synthetic versatility for modulating transparency and color allow perovskite solar cells (PSCs) to be an ideal solution for building-integrated photovoltaics (BIPVs), which transforms windows or façades into electric power generators. In this review, the unique features and properties of PSCs for BIPV application are accessed. Device engineering and optical management strategies of active layers, interlayers, and electrodes for semitransparent, bifacial, and colorful PSCs are also discussed. The performance of PSCs under conditions that are relevant for BIPV such as different operational temperature, light intensity, and light incident angle are also reviewed. Recent outdoor stability testing of PSCs in different countries and other demonstration of scalability and deployment of PSCs are also spotlighted. Finally, the current challenges and future opportunities for realizing perovskite-based BIPV are discussed.

Enhanced resistive switching performance in yttrium-doped CH3NH3PbI3 perovskite devices

In this study, yttrium-doped CH₃NH₃PbI₃ (Y-MAPbI₃) and pure CH₃NH₃PbI₃ (MAPbI₃) perovskite films have been fabricated using a one-step solution spin coating method in a glove box. X-ray diffractometry and field-emission scanning electron microscopy were used to characterize the crystal structures and morphologies of perovskite films, respectively. It was found that the orientation of the crystal changed and the grains became more uniform in Y-MAPbI₃ film, compared with the pure MAPbI₃ perovskite film. The films were used to prepare the resistive switching memory devices with the device structure of Al/Y-MAPbI₃ (MAPbI₃)/ITO-glass. The memory performance of both devices was studied and showed a bipolar resistive switching behavior. The Al/MAPbI₃/ITO device had an endurance of about 328 cycles. In contrast, the Al/Y-MAPbI₃/ITO device exhibited an enhanced performance with a long endurance up to 3000 cycles. Moreover, the Al/Y-MAPbI₃/ITO device also showed a higher ON/OFF ratio of over 10³, long retention time (≥10⁴ s), lower operation voltage (±0.5 V) and outstanding reproducibility. Additionally, the conduction mechanism of the high resistance state transformed from space-charge limited current for a Y free device to the Schottky emission after Y doping. The present results indicate that the Al/Y-MAPbI₃/ITO device has a great potential to be used in high-performance memory devices.

Chemical Vapor Deposited Mixed Metal Halide Perovskite Thin Films

In this article, we used a two-step chemical vapor deposition (CVD) method to synthesize methylammonium lead-tin triiodide perovskite films, MAPb_1−xSn_xI₃, with x varying from 0 to 1. We successfully controlled the concentration of Sn in the perovskite films and used Rutherford backscattering spectroscopy (RBS) to quantify the composition of the precursor films for conversion into perovskite films. According to the RBS results, increasing the SnCl₂ source amount in the reaction chamber translate into an increase in Sn concentration in the films. The crystal structure and the optical properties of perovskite films were examined by X-ray diffraction (XRD) and UV-Vis spectrometry. All the perovskite films depicted similar XRD patterns corresponding to a tetragonal structure with I4cm space group despite the precursor films having different crystal structures. The increasing concentration of Sn in the perovskite films linearly decreased the unit volume from about 988.4 ų for MAPbI₃ to about 983.3 ų for MAPb₀.₃₉Sn₀.₆₁I₃, which consequently influenced the optical properties of the films manifested by the decrease in energy bandgap (E_g) and an increase in the disorder in the band gap. The SEM micrographs depicted improvements in the grain size (0.3–1 µm) and surface coverage of the perovskite films compared with the precursor films.

Efficiency enhancement of perovskite solar cells by designing GeSe nanowires in the structure of the adsorbent layer

In this paper, coupled optical and electrical simulations of perovskite solar cells (PSCs) are performed to optimize their basis output parameters and obtain the best power conversion efficiency (PCE) based on both the light absorption and carrier transport mechanisms. Due to the limitations of perovskite absorption in longer wavelengths, we used an extra photo-active material of GeSe with a narrower bandgap and a broader absorbing spectrum to increase the efficiency of the PSC. To prevent carrier transmission disorder that exists in the planar structure with two absorbing materials, GeSe was inserted into the main active layer in the form of nanowires (NWs). As a result, it improved the carrier transfer and open-circuit voltage (V_oc ) in addition to the short-circuit current density (J_sc ). The behavior of PSC with different sizes of GeSe NWs at the same density was investigated to determine the appropriate size of NWs and achieve the highest PCE. In the optimal structure with 50 nm diameter NWs, J_sc and PCE of the cell are 22.96 mA cm^-2 and 18.97%, which are improvements of 39% and 50%, respectively, compared to the planar structure studied at the beginning of the paper.

Numerical study of a highly efficient light trapping nanostructure of perovskite solar cell on a textured silicon substrate

In this paper, a nanostructured perovskite solar cell (PSC) on a textured silicon substrate is examined, and its performance is analyzed. First, its configuration and the simulated unit cell are discussed, and its fabrication method is explained. In this proposed structure, poly-dimethylsiloxane (PDMS) is used instead of glass. It is shown that the use of PDMS dramatically reduces the reflection from the cell surface. Furthermore, the light absorption is found to be greatly increased due to the light trapping and plasmonic enhancement of the electric field in the active layer. Then, three different structures, are compared with the main proposed structure in terms of absorption, considering the imperfect fabrication conditions and the characteristics of the built PSC. The findings show that in the worst fabrication conditions considered structure (FCCS), short-circuit current density (Jsc) is 22.28 mA/cm2, which is 27% higher than that of the planar structure with a value of 17.51 mA/cm2. As a result, the efficiencies of these FCCSs are significant as well. In the main proposed structure, the power conversion efficiency (PCE) is observed to be improved by 32%, from 13.86% for the planar structure to 18.29%.

High-performance perovskite solar cell using photonic-plasmonic nanostructure

In this paper, a coupled optical-electrical modeling method is applied to simulate perovskite solar cells (PSCs) to find ways to improve light absorption by the active layer and ensure that the generated carriers are collected effectively. Initially, a planar structure of the PSC is investigated and its optical losses are determined. To reduce the losses and enhance collection efficiency, a convex light-trapping configuration of PSC is used and the impacts of these nanostructures on all parts of the cell are investigated. In this convex nanostructured PSC, the power conversion efficiency (PCE) is found to be increased when the thickness of the absorbing layer remained unchanged. Then, a plasmonic reflector is applied to trap light inside the perovskite. In this structure, by scattering light through the surface plasmon resonance (SPR) effect of the Au back-contact, the electromagnetic field is found to concentrate in the active layer. This results in increased perovskite absorption and, consequently, a high current density of the cell. In the final structure, which is the integration of these two structures, optical losses are found to be greatly diminished and the short-circuit current density (Jsc) is increased from 18.63 mA/cm2 for the planar structure to 23.5 mA/cm2 for the proposed structure. Due to the increased Jsc and open-circuit voltage (Voc) caused by the improved carrier collection, the PCE increases from 14.62 to 19.54%.

Optimizing Band Gap of Inorganic Halide Perovskites by Donor-Acceptor Pair Codoping

Inorganic halide perovskites (IHPs) are promising candidates for applications in solar cell devices. However, the band gaps of most IHPs are too large, so that the energy conversion efficiency is limited. In this work, we proposed a donor-acceptor pair codoping scheme to reduce the band gaps Sn- and Pb-based IHPs, based on first-principles calculations. Interestingly, the donor-acceptor pair codoping in CsSnBr₃ and CsPbI₃ can produce band gaps of 1.2 and 1.1 eV, respectively, both of which are close to the optimal band gap for solar cell materials. The absorption coefficient of donor-acceptor pair codoped CsSnBr₃ and CsPbI₃ in the visible light region are large, which indicates that they are good light absorbers for applications in solar cell devices.

Microwave-Assisted Preparation of Organo-Lead Halide Perovskite Single Crystals

The efficiency of organo-lead halide perovskite-based optoelectronic devices is dramatically lower for amorphous materials compared to highly crystalline ones. Therefore, it is challenging to optimize and scale up the production of large-sized single crystals of perovskite materials. Here, we describe a novel and original approach to preparing lead halide perovskite single crystals by applying microwave radiation during the crystallization. The microwave radiation primarily causes precise heating control in the whole volume and avoids temperature fluctuations. Moreover, this facile microwave-assisted method of preparation is highly reproducible and fully automated, it and can be applied for various different perovskite structures. In addition, this cost-effective method is expected to be easily scalable because of its versatility and low energy consumption. The crystallization process has low heat losses; therefore, only a low microwave reactor power of 8-15 W during the temperature changes and of less than 1 W during the temperature holding is needed.

Rational chemical doping of metal halide perovskites

Metal halide perovskites benefit from the combination of wide absorption, high carrier mobility, defect tolerance, moderate exciton binding energies, and versatility of solution processes, showing great promise in photovoltaics and optoelectronics. However, the issues of long-term instability and toxicity of lead are supposed to limit their further practical applications. Chemical doping of an impurity into metal halide perovskites was reported to be a relatively effective approach to solving these issues while providing additional tunable physical and chemical properties. In an attempt to boost the research field further, it is imperative to summarize the recent significant work on metal halide doped perovskites, disclosing the underlying structure-property relationships to provide useful insights into applications of these perovskites with high performance. In this review, we highlight the rational design of doped perovskites by both theoretical and experimental efforts as well as their potential application spanning various fields.

Invalidity of Band-Gap Engineering Concept for Bi3+ Heterovalent Doping in CsPbBr3 Halide Perovskite

Heterovalent CsPbBr₃ doping with Bi results in a significant red shift of the optical absorption of both single-crystal and powdered samples. The results of low-temperature (3.6 K) photoluminescence studies of perovskite single crystals indicate that the position of the excitonic luminescence peak remains unaffected by Bi doping that, in turn, infers that the band gap of Bi-doped perovskite is not changed as well. The position and state density distribution of the valence band and Fermi level of single-crystal perovskites were determined by another direct method of ultraviolet photoelectron spectroscopy. The obtained results show that Bi³⁺ doping causes no changes in the valence band structure but an increase in the Fermi level by 0.6 eV. The summary of the obtained results directly demonstrates that the concept of the band-gap engineering in Bi³⁺-doped CsPbBr₃ halide perovskite is not valid.