Ligang Yuan

An in situ vapor‐based halide exchange of the metal halide perovskite thin film patterns is demonstrated via stepwise conversion from PbI₂ patterns to CH₃NH₃PbI₃, directly followed by halide exchange via precursor switching (CH₃NH₃I → CH₃NH₃Br). Photodetector devices prepared from the completely exchanged CH₃NH₃PbBr₃ exhibit remarkable stability to air exposure and reversible performance via Br passivation of grain boundaries.

Abstract

Metal halide perovskites (MHPs) exhibit optoelectronic properties that are dependent on their ionic composition, and the feasible exploitation of these properties for device applications requires the ability to control the ionic composition integrated with the patterning process. Herein, the halide exchange process of MHP thin films directly combined with the patterning process via a vapor transport method is demonstrated. Specifically, the patterned arrays of CH₃NH₃PbBr₃ (MAPbBr₃) are obtained by stepwise conversion from polymer‐templated PbI₂ thin films to CH₃NH₃PbI₃ (MAPbI₃), followed by halide exchange via precursor switching from CH₃NH₃I to CH₃NH₃Br. It is confirmed that the phase transformation from MAPbI₃ patterns to MAPbBr₃ shows time‐ and position‐dependences on the substrate during halide exchange following the solid‐solution model with Avrami kinetics. The photodetectors fabricated from the completely exchanged MAPbBr₃ patterns display exceptional air stability and reversible detectivity from “apparent death” upon removing the adsorbed impurities, thereby suggesting the superior structural stability of perovskite patterns prepared through vapor‐phase halide exchange. The results demonstrate the potential of chemical vapor deposition patterning of MHP materials in multicomponent optoelectronic device systems.

Publication date: 15 June 2021

Source: Chemical Engineering Journal, Volume 414

Author(s): Cong Geng, Peng Wei, Huamei Chen, Haichao Liu, Shenshen Zheng, Haobin Wang, Yahong Xie

This Review describes approaches to improve the performance of PEDOT:PSS/Si hybrid solar cells. The main strategies include modifying PEDOT:PSS, optimizing the light‐trapping effect, passivating the silicon surface, inserting an interface layer, and improving the back contact and the transparent conductive electrode.

Abstract

The emerging energy crisis has focused significant worldwide attention on solar cells. Although crystalline silicon solar cells are currently widely used, their high cost limits the development of solar power generation. Consequently, hybrid solar cells are becoming increasingly important, especially organic‐Si hybrid solar cells (HSCs). Organic‐Si HSCs combine a mature technology and high efficiency with the low‐temperature manufacturing process and tunable optoelectronic properties of organic solar cells. The organic material can be P3HT, carbon nanotubes, graphene, and PEDOT:PSS. Here we review the performance of PEDOT:PSS/Si HSCs and methods for improving their efficiency, such as PEDOT:PSS modification, optimization of the trapping effect, passivation of the silicon surface, addition of an interface layer, improvement of a back contact, and optimization of the metal top electrode. This Review should help fill the gap in this area and provide perspectives for the future development of the PEDOT:PSS/Si HSCs.

The carbon‐based hole‐transporting material (HTM)‐free CsPbBr₃ perovskite solar cell (PSC) achieves a maximized power conversion efficiency (PCE) of 9.82% with an excellent thermal and moisture stability through perovskite film management and multiple‐ionic defect passivation by the introduction of a tetra‐bisphenol A (TBBPA) additive.

High‐quality perovskite films with low imperfections, high hole mobility, and matching energy levels play a crucial role in enhancing performance of perovskite solar cells (PSCs) without hole‐transporting materials (HTMs). Herein, it is demonstrated that the incorporation of a stable tetra‐bisphenol A (TBBPA) with diphenyl ring, polybromides, and hydroxyl groups additive into a perovskite film can simultaneously manipulate the crystal growth and passivate the defects through coordination interaction between the functional group (OH, Br) and the unsaturated halogen and metal ions (Br⁻, Cs⁺, and Pb²⁺), resulting in a reduced grain boundary as well as imperfection and increased hole mobility of the CsPbBr₃ perovskite film. In addition, the valence band of a perovskite film with TBBPA additive is shifted upward to approach the work function of the carbon electrode, thereby improving the energy level alignment. Consequently, a significantly boosted charge extraction and reduced charge recombination of the carbon‐based HTM‐free CsPbBr₃ PSCs is obtained after incorporating the TBBPA additive, yielding a maximum power conversion efficiency of up to 9.82% of the optimized device. Furthermore, the champion PSC without encapsulation displays a remarkable thermal and moisture stability after being kept in ambient air for 720 h at 85 °C and 85% relative humidity, respectively.

Highly efficient CsPbI_1.5Br_1.5 perovskite solar cells (PSCs) are achieved via introducing fluorescein isothiocyanate (FITC) organic dye as passivator. FITC not only reduces the metal ion related trap states but also improves film crystallinity, resulting in an enhancement of device efficiency from 12.3% to 14.05%. In addition, it is demonstrated that CsPbI_1.5Br_1.5 perovskite shows the optimal halide composition for inorganic PSCs.

Abstract

All‐inorganic perovskite solar cells (PSCs) have recently received growing attention as a promising template to solve the thermal instability of organic–inorganic PSCs. However, the thermodynamic phase instability and relatively low device efficiency pose challenges. Herein, highly efficient and stable CsPbI_1.5Br_1.5 compositional perovskite‐based inorganic PSCs are fabricated using an organic dye, fluorescein isothiocyanate (FITC), as a passivator. The carboxyl and thiocyanate groups of FITC not only minimize the trap states by forming interactions with the under‐coordinated Pb²⁺ ions but also significantly increase the grain size and improve the crystallinity of the perovskite films during annealing. Consequently, perovskite films with superior optoelectronic properties, prolonged carrier lifetime, reduced trap density, and improved stability are obtained. The resulting device yields a champion efficiency of 14.05% with negligible hysteresis, which presents the highest reported efficiency for inorganic CsPbI_1.5Br_1.5 solar cells reported thus far. In addition, FITC can be generally adopted as attractive passivator to improve the performance of CsPbI₂Br‐ and CsPbIBr₂‐based PSCs. Furthermore, with a comprehensive comparison of mixed‐halide inorganic perovskites, it is demonstrated that CsPbI_1.5Br_1.5 compositional perovskite is a promising candidate with the optimal halide composition for high‐performance inorganic PSCs.

High efficiency and humidity‐resistant flexible perovskite solar cells (FPSCs) are fabricated, using a SnO₂/Al(acac)₃ bilayer as the electron transfer layer. FPSCs present long‐time stability in ambient conditions (>50% relative humidity) without encapsulation, while yielding a power conversion efficiency (PCE) of up to 20.87%. That may open a new way to improve the stability of FPSCs.

Flexible perovskite solar cells (FPSCs) with high efficiency and excellent mechanical flexible properties have attracted enormous interest as a promising photovoltaic technology in recent years. However, the performance or stability of FPSCs is still far inferior to that of conventional glass‐based perovskite solar cells (PSCs). Herein, a cross‐linking agent called aluminum acetylacetonate (Al(acac)₃) is introduced as an interface layer between electron transport layer and perovskite absorber. Due to the well‐matched energy levels and improved grain size and crystallinity of the perovskite, a champion device with the highest power conversion efficiency (PCE) of 20.87% is achieved on the FPSCs. The device retains about 80% of its initial performance after 1000 h under >50% relative humidity without encapsulation. In addition, attributed to the Al(acac)₃ super bending resistance, more than 91% of the original PCE is retained after 1500 bending cycles. This work proposes the substrate side optimization for improving device efficiency and stability which may provide a novel concept for promoting the development of FPSCs.

A systematic summary of the use of fluorinated compounds in each layer of perovskite solar cells is reviewed. Fluorinated compounds induce better electron and hole transporting material quality. The high electronegativity of the fluorine element allows an efficient charge‐extraction and transport at the perovskite surface and interfaces. More importantly, these fluorinated compounds greatly enhance both device efficiency and long‐term stability.

Abstract

Several valuable scientific investigations have been conducted these last few years in materials design and device engineering for perovskite solar cells (PSCs) to make them competitive compared to traditional silicon‐based photovoltaic technologies. Consequently, high power conversion efficiency beyond 25% is nowadays reported. However, their long‐term stability remains a significant challenge to overcome. Herein, the influence of fluorinated compounds on each layer of PSCs devices and their impact on the resulted device performances and stability is spotlighted. The fluorinated compounds exhibit attractive properties due to their very high electronegativity attributed to the fluorine atom, and their strong hydrophobicity. Thus, the introduction of these compounds is found to be a successful strategy to positively suppress the surface trap states, enhancing charge collection and reducing interfacial charge recombination. Besides, a better film quality and better energy level alignment is obtained, resulting in the improvement of device photovoltaic parameters such as the open‐circuit voltage (V _oc), short‐circuit current (J _sc), and fill factor (FF), and then, the device's overall power conversion efficiency (PCE). Their long‐term stability is also found to further be improved.

An ionic liquid, 1,3‐dimethyl‐3‐imidazolium hexafluorophosphate (DMIMPF₆), was used to passivate a perovskite to decrease the defects of Pb‐cluster and Pb‐I antisite, thereby reducing the energy barrier between the perovskite and hole transport layer. A perovskite solar cell attained a 23.25 % efficiency with a high stability due to hydrophobic DMIMPF₆.

Abstract

Surface defects have been a key constraint for perovskite photovoltaics. Herein, 1,3‐dimethyl‐3‐imidazolium hexafluorophosphate (DMIMPF₆) ionic liquid (IL) is adopted to passivate the surface of a formamidinium‐cesium lead iodide perovskite (Cs_0.08FA_0.92PbI₃) and also reduce the energy barrier between the perovskite and hole transport layer. Theoretical simulations and experimental results demonstrate that Pb‐cluster and Pb‐I antisite defects can be effectively passivated by [DMIM]⁺ bonding with the Pb²⁺ ion on the perovskite surface, leading to significantly suppressed non‐radiative recombination. As a result, the solar cell efficiency was increased to 23.25 % from 21.09 %. Meanwhile, the DMIMPF₆‐treated perovskite device demonstrated long‐term stability because the hydrophobic DMIMPF₆ layer blocked moisture permeation.

Over 23% efficiency is achieved using a stabilized phenyl‐C₆₁‐butyric acid methyl ester (PCBM):bathophenanthroline (Bphen) interlayer in SnO₂‐based perovskite solar cells, which can retain over 92% of their initial efficiency after 1000 h continuous illumination of maximum power point tracking at 60 °C.

Abstract

It is crucial to make perovskite solar cells sustainable and have a stable operation under natural light soaking before they become commercially acceptable. Herein, a small amount of the small molecule bathophenanthroline (Bphen) is introduced into [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester and it is found that Bphen can stabilize the C₆₀‐cage well through formation of much more thermodynamically stable charge‐transfer complexes. Such a strengthened complex is used as an interlayer at the in‐light perovskite/SnO₂ side to achieve a champion device with efficiency of 23.09% (certified 22.85%). Most importantly, the stability of the resulting devices can be close to meeting the requirements of the International Electrotechnical Commission 61215 standard under simulated UV preconditioning and light‐soaking testing. They can retain over 95% and 92% of their initial efficiencies after 1100 h UV irradiation and 1000 h continuous illumination of maximum power point tracking at 60 °C, respectively.

A thermally stable perovskite solar cell is developed by capturing mobile lithium ions using a new molecular hole transporter, 1,3‐bis(5‐(4‐(bis(4‐methoxyphenyl)amino)phenyl)thieno[3,2‐b]thiophen‐2‐yl)‐5‐octyl‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (coded HL38), where a strong interaction of the lithium ions in lithium bis(trifluoromethanesulfonyl)imide with the 5‐octylthieno[3,4‐c]pyrrole‐4,6‐dione (octyl‐TPD) moiety in HL38 is responsible for maintaining ≈86% of the initial power conversion efficiency for over 1000 h at 85 °C.

Abstract

A thermally stable perovskite solar cell (PSC) based on a new molecular hole transporter (MHT) of 1,3‐bis(5‐(4‐(bis(4‐methoxyphenyl) amino)phenyl)thieno[3,2‐b]thiophen‐2‐yl)‐5‐octyl‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (coded HL38) is reported. Hole mobility of 1.36 × 10⁻³ cm² V⁻¹ s⁻¹ and glass transition temperature of 92.2 °C are determined for the HL38 doped with lithium bis(trifluoromethanesulfonyl)imide and 4‐tert‐butylpyridine as additives. Interface engineering with 2‐(2‐aminoethyl)thiophene hydroiodide (2‐TEAI) between the perovskite and the HL38 improves the power conversion efficiency (PCE) from 19.60% (untreated) to 21.98%, and this champion PCE is even higher than that of the additive‐containing 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐MeOTAD)‐based device (21.15%). Thermal stability testing at 85 °C for over 1000 h shows that the HL38‐based PSC retains 85.9% of the initial PCE, while the spiro‐MeOTAD‐based PSC degrades unrecoverably from 21.1% to 5.8%. Time‐of‐flight secondary‐ion mass spectrometry studies combined with Fourier transform infrared spectroscopy reveal that HL38 shows lower lithium ion diffusivity than spiro‐MeOTAD due to a strong complexation of the Li⁺ with HL38, which is responsible for the higher degree of thermal stability. This work delivers an important message that capturing mobile Li⁺ in a hole‐transporting layer is critical in designing novel MHTs for improving the thermal stability of PSCs. In addition, it also highlights the impact of interface design on non‐conventional MHTs.

The strong interaction between F and Sn changes the electron cloud density around Sn atoms by introducing RbF into SnO₂ colloidal dispersion, contributing to the improved electron mobility of SnO₂. While spin‐coating RbF onto the SnO₂ surface, the Rb⁺ cations escape into the bulk perovskite, which inhibits ion migration and decreases the trap density.

Abstract

Regulating the electron transport layer (ETL) has been an effective way to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs) as well as suppress their hysteresis. Herein, the SnO₂ ETL using a cost‐effective modification material rubidium fluoride (RbF) is modified in two methods: 1) adding RbF into SnO₂ colloidal dispersion, F and Sn have a strong interaction, confirmed via X‐ray photoelectron spectra and density functional theory results, contributing to the improved electron mobility of SnO₂; 2) depositing RbF at the SnO₂/perovskite interface, Rb⁺ cations actively escape into the interstitial sites of the perovskite lattice to inhibit ions migration and reduce non‐radiative recombination, which dedicates to the improved open‐circuit voltage (V _oc) for the PSCs with suppressed hysteresis. In addition, double‐sided passivated PSCs, RbF on the SnO₂ surface, and p‐methoxyphenethylammonium iodide on the perovskite surface, produces an outstanding PCE of 23.38% with a V _oc of 1.213 V, corresponding to an extremely small V _oc deficit of 0.347 V.

A 2D zinc‐based metal–organic frameworks (MOFs) with plenty of active sites are prepared through a molecular self‐assembly strategy and used to solve the incompatibility between MOFs and perovskite films. The tunable crystallographic orientation and functionalized framework of this material are considered for regulating the photovoltaic performance and stability of perovskite solar cells.

Abstract

Perovskite degradation induced by surface defects and imperfect grain boundaries of films seriously damages the performance of perovskite solar cells (PSCs). Meanwhile, conventional organic molecules cannot maintain the long‐time passivation effects under the stimulation of external environmental factors. Here, efficient and stable grain passivation in perovskite films is realized by preparing formic acid‐functionalized 2D metal–organic frameworks (MOFs) as the terminated agent. Through robust interactions between exposed active sites and PbI₂, the 2D MOFs tightly caps the surface of PbI₂‐terminated perovskite grains to stabilize the perovskite phases and aids the adhesion of adjacent grains. The MOFs mainly distributed at the grain boundaries of the perovskite film is directly observed at the microscopic scale. The modified perovskite films have regular morphology, lower defect density, and superior optoelectronic properties. Benefiting from the suppressed charge recombination and faster charge extraction, a power conversion efficiency of 21.28% is achieved for the best‐performing PSC device. The unencapsulated PSCs with the MOFs modification maintain 88% and 81% of their initial efficiency after 750 h heating at 85 °C under N₂ atmosphere and more than 1000 h storage in ambient environment (25 °C, RH ≈ 40%), respectively.

Semiconducting oxide overlayer materials (SOOMs) can offer a new way for low-cost and highly-stable halide perovskite solar cells (HPSCs) compared to organic semiconducting overlayer materials. The effective deposition of SOOMs on top of the perovskite layer is expected to contribute to the commercialization of single-junction as well as multi-junction HPSCs.

Abstract

Halide perovskite solar cells (HPSCs) contain charge transport layers (CTLs) both above and below the photoactive perovskite layer. These semiconducting CTLs are just as important as the perovskite layer to fully realizing the potential of perovskite materials. In particular, semiconducting oxide overlayer materials (SOOMs) are expected to lower costs and provide better long-term stability compared to the organic semiconducting materials commonly used for the upper layer. However, SOOM-based HPSCs are currently less efficient than conventional devices owing to SOOM's deposition constraints imposed by the underlying perovskite layer. This progress report focuses on the recent evolution of SOOM-based HPSCs by describing the key issues and recent advances in SOOM deposition methods. Finally, remaining challenges and future research directions for SOOMs are discussed to provide guidance toward the commercialization of HPSCs.

Harmful UV light and surface defects accelerate the degradation of perovskite solar cells (PSCs). A tautomeric “sunscreen” molecule can be used to protect the PSC from UV degradation and enable molecular defect passivation (defect formation energy: −1.35 eV) through interactions between functional groups and defects. This strategy provides high‐efficiency PSCs with long‐term UV stability.

Abstract

UV light always does great harm to perovskite solar cells, relentlessly degrading perovskites and shortening the lifetime of perovskite devices. Meanwhile, surface defects in perovskite films further accelerate the degradation process and serve as nonradiative charge recombination centers to deteriorate device efficiency. Herein, we demonstrate that a “sunscreen” molecule, 2‐hydroxy‐4‐methoxybenzophenone, not only protects the perovskite solar cell from UV degradation but also enables molecular defect passivation through interaction between functional groups and defects by molecular tautomerism under UV light illumination. Therefore, the sunscreen strategy efficiently enhances the UV endurance of PSCs and improves defect formation energy to −1.35 eV. The perovskite solar cell with sunscreen (sunscreen PSC) exhibits outstanding efficiencies of up to 23.09 % (0.04 cm²) and 19.73 % (1.00 cm²) as well as long‐term UV (UVa: 365 nm and UVb: 285 nm) stability.

Publication date: 15 May 2021

Source: Chemical Engineering Journal, Volume 412

Author(s): Wenxiao Zhang, Xiaodong Li, Xiuxiu Feng, Xiaoyan Zhao, Junfeng Fang

Inorganic perovskite CsPbI₂Br is applied to prepare high‐performance semitransparent perovskite solar cells (ST‐PSCs). (Chloromethylene)‐dimethylammonium chloride as an additive is introduced into the perovskite precursor to favor high‐quality CsPbI₂Br perovskite films. Through optimizing the perovskite film, interface, and electrode type, the efficiency of the ST‐PSC reaches 14.01% and 10.36% under an average visible transmittance (AVT) of 31.7% and 40.9%, respectively.

Abstract

Thanks to the tunable bandgap and excellent photoelectric characteristics, perovskites have been widely used in semitransparent solar cells (ST‐SCs). Most works present unsatisfactory power conversion efficiencies (PCEs) through reducing the thickness of the perovskite films because there is a trade‐off between PCE and average visible transmittance (AVT). As a consequence, most PCEs are less than 12% when the AVT is higher than 20% due to the limited voltage (V _oc) and short‐circuit current (J _sc). Herein, a strategy of intermediate adduct (IMAT) engineering is developed to improve the film quality of the inorganic perovskite CsPbI₂Br, which is a challenging issue to limit its performance of efficiency and stability. A normal n–i–p‐structured PSC based on the optimal CsPbI₂Br film delivers a PCE of 16.02% with excellent stability. Furthermore, through optimizing the electrode type and interface, the ST‐PSC shows a high V _oc larger than 1.2 V and the PCE reaches 14.01% and 10.36% under an AVT of 31.7% and 40.9%, respectively. This is the first demonstration of a CsPbI₂Br ST‐PSC, and it outperforms most of other types of perovskites.

A low‐cost industrial organic pigment, quinacridone (QA), was applied as surface passivation agent for perovskite solar cells (PSCs) by solution processing of a soluble QA derivative followed by thermal annealing to convert it into insoluble QA. Passivation with strong interactions between QA molecules and metal halides, together with the hydrophobicity of QA coating, enabled highly efficient PSCs with remarkable stability.

Abstract

Surface passivation of perovskite solar cells (PSCs) using a low‐cost industrial organic pigment quinacridone (QA) is presented. The procedure involves solution processing a soluble derivative of QA, N,N‐bis(tert‐butyloxycarbonyl)‐quinacridone (TBOC‐QA), followed by thermal annealing to convert TBOC‐QA into insoluble QA. With halide perovskite thin films coated by QA, PSCs based on methylammonium lead iodide (MAPbI₃) showed significantly improved performance with remarkable stability. A PCE of 21.1 % was achieved, which is much higher than 18.9 % recorded for the unmodified devices. The QA coating with exceptional insolubility and hydrophobicity also led to greatly enhanced contact angle from 35.6° for the pristine MAPbI₃ thin films to 77.2° for QA coated MAPbI₃ thin films. The stability of QA passivated MAPbI₃ perovskite thin films and PSCs were significantly enhanced, retaining about 90 % of the initial efficiencies after more than 1000 hours storage under ambient conditions.

The addition of the correct amounts of dimethyl sulfoxide (DMSO) with 2‐methoxyethanol (2‐ME) perovskite precursor ink is a crucial step toward reproducible slot‐die coatings and highly efficient perovskite solar cells. Through observing the drying process of 2ME‐DMSO inks from in situ X‐ray diffraction experiments, it is demonstrated that 11.77 mol% DMSO favorably affects thin film growth.

Abstract

Solar cells incorporating metal‐halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution‐processed solar cell devices. Scaling MHP‐based devices to larger area prototypes requires the development and optimization of scalable process technology and ink formulations that enable reproducible coating results. It is demonstrated that the power conversion efficiency (PCE) of small‐area methylammonium lead iodide (MAPbI₃) devices, slot‐die coated from a 2‐methoxy‐ethanol (2‐ME) based ink with dimethyl‐sulfoxide (DMSO) used as an additive depends on the amount of DMSO and age of the ink formulation. When adding 12 mol% of DMSO, small‐area devices of high performance (20.8%) are achieved. The effect of DMSO content and age on the thin film morphology and device performance through in situ X‐ray diffraction and small‐angle X‐ray scattering experiments is rationalized. Adding a limited amount of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI₃ and 2‐ME (MAPbI₃‐2‐ME) and induces the formation of the MAPbI₃ perovskite phase. Higher DMSO content leads to the precipitation of the (DMSO)₂MA₂Pb₃I₈ intermediate phase that negatively affects the thin‐film morphology. These results demonstrate that rational insights into the ink composition and process control are critical to enable reproducible large‐scale manufacturing of MHP‐based devices for commercial applications.

High performance perovskite solar modules (PSMs) are fabricated by introducing NH₄Cl to induce the formation of the intermediate phases. The PSMs show long‐term operational stability with a T ₈₀ lifetime under continuous light illumination exceeding 1600 h for a 5 × 5 cm² solar module and 1100 h for a 10 × 10 cm² solar module.

Abstract

In addition to high efficiencies, upscaling and long‐term operational stability are key pre‐requisites for moving perovskite solar cells toward commercial applications. In this work, a strategy to fabricate large‐area uniform and dense perovskite films with a thickness over one‐micrometer via a two‐step coating process by introducing NH₄Cl as an additive in the PbI₂ precursor solution is developed. Incorporation of NH₄Cl induces the formation of the intermediate phases of x[NH₄ ⁺]·[PbI₂Cl _x ] ^{x −} and HPbI_{3− x} Cl _x , which can effectively retard the crystallization rate of perovskite leading to uniform and compact full‐coverage perovskite layers across large areas with high crystallinity, large grain sizes, and small surface roughness. The 5 × 5 and 10 × 10 cm² perovskite solar modules (PSMs) based on this method achieve a power conversion efficiency (PCE) of 14.55% and 10.25%, respectively. These PSMs also exhibit good operational stability with a T ₈₀ lifetime (the time during which the solar module PCE drops to 80% of its initial value) under continuous light illumination exceeding 1600 h (5 × 5 cm²) and 1100 h (10 × 10 cm²), respectively.

Publication date: 1 May 2021

Source: Chemical Engineering Journal, Volume 411

Author(s): Tanghao Liu, Zhipeng Zhang, Qi Wei, Bingzhe Wang, Kaiyang Wang, Jia Guo, Chao Liang, Dandan Zhao, Shi Chen, Yuxin Tang, Yuanyuan Zhou, Guichuan Xing

Publication date: 20 January 2021

Source: Joule, Volume 5, Issue 1

Author(s): Tianqi Niu, Weiya Zhu, Yiheng Zhang, Qifan Xue, Xuechen Jiao, Zijie Wang, Yue-Min Xie, Ping Li, Runfeng Chen, Fei Huang, Yuan Li, Hin-Lap Yip, Yong Cao

The possible side reaction in the lead iodide solution of formamidinium is studied, and phenylboric acid (PBA) is introduced as a stabilizer in the perovskite precursor solution, which can inhibit the side reaction, thus greatly improving the stability of the perovskite solar cell.

The instability of the perovskite precursor solution seriously affects the purity of the perovskite films, which is one of the key factors for the low reproducibility for highly efficient devices. Formamidinium‐based perovskite with more suitable spectral absorption range and higher thermal stability has become the mainstream material. However, the side reactions in pure formamidinium lead iodide solution have not been fully revealed. Herein, it is demonstrated that self‐condensation of formamidinium iodide occurs to form the by‐product s‐triazine, and its content increases with the aging time of the solution. It is also discovered that phenylboric acid (PBA) can effectively inhibit the self‐condensation reaction and the content of the s‐triazine is decreased by more than 95% in the solution aging at 60 °C for 7 days. The PBA used as the stabilizer not only enhances purity and decreases defect density of the perovskite films but also strongly enhances the reproducibility for highly efficient perovskite solar cells.

Bromide‐based organo‐metal halide perovskites have shown great potential for use in tandem solar cells, LEDs and photodetectors. Here, we report a new protocol using a one‐step deposition method for producing formamidinium lead bromide (FAPbBr₃) perovskites, which features a solvent engineered intermediate phase to achieve superior films. For the first time, an FABr‐PbBr₂‐DMSO intermediate is identified and single crystals of the same intermediate compound have been synthesized. A systematic investigation of phase evolution in the film formation process reveals that DMSO enables crystallization of the FABr‐PbBr₂‐DMSO intermediate, and thus modulates the crystallization process of FAPbBr₃ perovskite, achieving uniform, smooth films with Volmer–Weber morphology. To prevent hole leakage arising from the larger bandgap of FAPbBr₃ than FAPbI₃, we added an additional layer of Mg‐doped ZnO nanoparticles. As a result, inverted solar cells using these solvent engineered films can achieve power conversion efficiencies (PCEs) of up to 9.06 %, the highest reported efficiency for inverted FAPbBr₃ perovskite devices.

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Publication date: 1 May 2021

Source: Chemical Engineering Journal, Volume 411

Author(s): Md. Shahiduzzaman, Ersan Y. Muslih, A.K. Mahmud Hasan, LiangLe Wang, Shoko Fukaya, Masahiro Nakano, Makoto Karakawa, Kohshin Takahashi, Md. Akhtaruzzaman, Jean-Michel Nunzi, Tetsuya Taima

Publication date: 17 February 2021

Source: Joule, Volume 5, Issue 2

Author(s): Shaobing Xiong, Zhangyu Hou, Shijie Zou, Xiaoshuang Lu, Jianming Yang, Tianyu Hao, Zihao Zhou, Jianhua Xu, Yihan Zeng, Wei Xiao, Wei Dong, Danqin Li, Xiang Wang, Zhigao Hu, Lin Sun, Yuning Wu, Xianjie Liu, Liming Ding, Zhenrong Sun, Mats Fahlman