JIALINGBO

Self-assembled monolayers (SAM) modified nickel oxide (NiO_x) is used as a hole-selective layer in inverted perovskite solar cells and finally, the highest power conversion efficiency of 24.8% is achieved with excellent thermal stability by the highest coverage of SAM on NiO_x.

Abstract

Nickel oxide is one of the most promising hole-transporting materials in inverted perovskite solar cells (PSCs) but suffers from undesired reactions with perovskite which leads to limited device performance and stability. Self-assembled monolayers (SAMs) are demonstrated to effectively optimize the NiO_x/perovskite interface, but the significance of the compactness of the SAM at the interface is less investigated. Here, a series of methoxy-substituted triphenylamine functionalized benzothiadiazole (TBT) based SAM molecules, TBT-BA, TBT-FBA, and TBT-DBA, with benzoic acid, 2-fluorobenzoic acid and isophthalic acids as anchoring groups are used to modify NiO_x. TBT-BA with the simplest structure is demonstrated to form the densest SAM on NiO_x, thus optimized NiO_x/SAM/perovskite interface is achieved with enhanced charge collection and suppressed interfacial reaction and recombination. TBT-BA can also passivate the perovskite most effectively due to the highest binding energy toward perovskite, thus the corresponding inverted PSCs show the highest PCE of 24.8% and maintain 88.7% of the initial PCE after storage at 60 °C for 2635 h in the glovebox. The work provides important insights into designing SAM molecules for modification transporting layers for efficient and stable PSCs.

This work reports a photochemistry-based p-doping mechanism of spiro-OMeTAD. Metal cations (Y3+ or La3+)-tBP complexes catalyze the fast quenching of photo-excited spiro-OMeTAD via a symmetry-breaking charge separation process. This photo-doping method yields spiro-OMeTAD+ through the oxidation of spiro anions by trace of oxidizer. This photo-doping method can prevent unintended oxidation and dopant-mediated degradation due to no additional aging or ion penetration. The photo-doped perovskite solar cell shows far superior operational stability and maintains excellent efficiency under full sun illumination over 1,000 h.

A new all-perovskite tandem solar cell structure, with 3T back-contact all-perovskite tandem solar cell structure effectively avoids the current matching of 2T tandem solar cell and the light loss of 4T tandem solar cell. The feasibility of the 3T back-contact all-perovskite tandem solar cell is verified by the simulation method.

Abstract

The development of efficient all perovskite tandem solar cells has faced challenges related to current matching and optical losses. In this work, a design of a non-coplanar three-terminal (3T) all perovskite tandem solar cell is presented, which consists of a p-i-n inverted NiO_X-based CsPbI₂Br perovskite top cell, and a FA_0.6MA_0.4Sn_0.5Pb_0.5I₃ perovskite bottom cell with back-contact (BC) device structure. It effectively mitigated the optical losses introduced in non-absorbing layers and resulted in a 2.9% absolute efficiency improvement compared to that of planar sandwich-type 3T tandems. Both optical and electrical characteristics of the multi-terminal tandem cells are investigated. Then, it is focused on understanding the impact of top cell thickness on overall non-coplanar BC 3T-tandem performance, considering low-energy photon optical reflection and carrier transport distance. Following optimizations of energy level and device structure, an efficiency of 32.16% is achieved, with non-coplanar BC 3T device architecture: top cell consisting of hole extraction layer (ITO/NiOx), CsPbI₂Br absorber layer, and electron extraction layer (ZnO/FA_0.6MA_0.4Sn_0.5Pb_0.5I₃/SnO₂/Ag); and bottom cell (Ni/NiOx/FA_0.6MA_0.4Sn_0.5Pb_0.5I₃/SnO₂/Ag); bottom perovskite layer has two functions, one is electron transport layer for top cell, and the other is low-energy photon absorption layer in bottom cell. It provides insight and a promising pathway for manufacturing high-efficient all perovskite tandem solar cells.

2D/3D wide-bandgap perovskites are successfully constructed using 1-TzFACl as a spacer. The 2D/3D perovskite exhibits better film quality, enhanced crystallinity, and suppressed nonradiative recombination losses. The optimized device based on 2D/3D perovskite shows an efficiency of 21.58% with enhanced phase stability. An efficiency of 25.66% and improved light stability are achieved for monolithic 2-terminal perovskite/silicon tandem solar cells.

To maximize the power conversion efficiency (PCE) and stability of perovskite/silicon tandem solar cells (TSCs), high-performance and stable perovskite top cells with wide-bandgaps are required. A 2D/3D wide-bandgap perovskite with a bandgap of 1.69 eV using 1H-1,2,4-triazole-1-carboximidamide (1-TzFACl) as a spacer is developed. The 2D/3D wide-bandgap perovskite shows better film quality, enhanced crystallinity, suppressed nonradiative recombination, and significantly improved phase stability. Its initial PCE (21.58%) remains above 87% after 1560 h of continuous illumination due to the insertion of Cl⁻ in the perovskite lattice. A monolithic two-terminal perovskite/silicon TSC achieves a PCE of 25.66% with high light stability. This work provides an ingenious strategy to restrain the phase segregation in wide-bandgap perovskites, leading to effective and stable perovskite/silicon TSCs.

In recent years, self-assembled monolayers (SAMs) have been investigated as a fascinating hole-selective contact for inverted positive-intrinsic-negative (p-i-n) perovskite solar cells (IPSCs). Here, the rapid progress of the IPSCs based on SAMs is comprehensively reviewed from the aspects of efficiency and stability progress, device up-scaling issues, and cost analysis.

Abstract

Inverted positive-intrinsic-negative (p-i-n) perovskite solar cells (IPSCs) have attracted widespread attention due to their low fabrication temperature, good stability in ambient air, and the potential for use in flexible and tandem devices. In recent years, self-assembled monolayers (SAMs) have been investigated as a promising hole-selective contact for IPSCs, leading to an impressive record efficiency of about 26%, which is comparable to that of the regular n-i-p counterparts. This review focuses on the progress of SAM-based IPSCs from the perspective of energy level matching, defect passivation, interface carrier extraction, and SAMs’ stability improvement, as well as the advances in up-scalable fabrication of SAMs and perovskite layers for efficient solar modules and tandem devices. A cost analysis of the SAMs and other commonly used hole-selective materials is conducted to evaluate their cost-effectiveness for photovoltaic applications. Finally, the future challenges are pointed out and the perspectives on how to up-scale SAM-based IPSCs and improve their long-term operational stability are provided.

The introduction of choline acetate alongside the perovskite precursors triggers the formation of a 1D/3D perovskite heterojunction at the buried interface of the active layer. Due to enhanced homogeneity, defect passivation, and improved interfacial energy alignment, inverted architecture perovskite solar cells reach a maximum photovoltaic efficiency of >24% with improved stability.

Abstract

Interfacial modification is a key strategy for improving the performance of perovskite photovoltaic devices. While the modification of the top surface of the perovskite active layer is well established, engineering of the buried interface is highly challenging. Here, the spontaneous formation of a 1D/3D perovskite heterojunction at the buried interface of a perovskite active layer by incorporating choline acetate alongside the perovskite precursors is reported. Importantly, extensive spectroscopic and microscopic characterization and solid-state nuclear magnetic resonance experiments demonstrate the formation of phase-pure 1D and 3D domains. The 1D/3D junction results in a suppression of the defect states and an improved energetic level alignment at the buried interface, leading to a maximum power conversion efficiency of >24% when incorporated in inverted architecture perovskite solar cells. This work introduces a versatile approach to the modification of the buried interface of the perovskite active layer.

A unique intermediate phase engineering strategy is developed to overcome the residual of solvent in unannealed perovskite film by introducing octane-1,8-diamine dihydroiodide. This helps to achieve single junction wide bandgap perovskite solar cells with high efficiency >22% and outstanding stability, and achieve high performance 4-terminal all perovskite and large area perovskite solar cells.

Abstract

Wide bandgap (WBG) perovskite can construct tandem cells with narrow bandgap solar cells by adjusting the band gap to overcome the Shockley−Queisser limitation of single junction perovskite solar cells (PSCs). However, WBG perovskites still suffer from severe nonradiative carrier recombination and large open-circuit voltage loss. Here, this work uses an in situ photoluminescence (PL) measurement to monitor the intermediate phase evolution and crystallization process via blade coating. This work reports a strategy to fabricate efficient and stable WBG perovskite solar cells through doping a long carbon chain molecule octane-1,8-diamine dihydroiodide (ODADI). It is found that ODADI doping not only suppresses intermediate phases but also promote the crystallization of perovskite and passivate defects in blade coated 1.67 eV WBG FA_0.7Cs_0.25MA_0.05Pb(I_0.8Br_0.2)₃ perovskite films. As a result, the champion single junction inverted PSCs deliver the efficiencies of 22.06% and 19.63% for the active area of 0.07 and 1.02 cm², respectively, which are the highest power conversion efficiencies (PCEs) in WBG PSCs by blade coating. The unencapsulated device demonstrates excellent stability in air, which maintains its initial efficiency at the maximum power points under constant AM 1.5G illumination in open air for nearly 500 h. The resulting semitransparent WBG device delivers a high PCE of 20.06%, and the 4-terminal all-perovskite tandem device delivers a PCE of 28.35%.

A top-down engineering strategy of perovskite crystallization is introduced via propylamine chloride (PACl) post treatment of perovskite wet film, inducing downward preferred crystallization orientation and realizing excellent homogeneity in terms of vertical and horizontal scale of perovskite, contributing to a champion PCE of 25.07% for p-i-n PVSCs, as well as the enhanced thermal and operational stability.

Abstract

Crystallization orientation plays a crucial role in determining the performance and stability of perovskite solar cells (PVSCs), whereas effective strategies for realizing oriented perovskite crystallization is still lacking. Herein, a facile and efficient top-down strategy is reported to manipulate the crystallization orientation via treating perovskite wet film with propylamine chloride (PACl) before annealing. The PA⁺ ions tend to be adsorbed on the (001) facet of the perovskite surface, resulting in the reduced cleavage energy to induce (001) orientation-dominated growth of perovskite film and then reduce the temperature of phase transition, meanwhile, the penetrating Cl ions further regulate the crystallization process. As-prepared (001)-dominant perovskite films exhibit the ameliorative film homogeneity in terms of vertical and horizontal scale, leading to alleviated lattice mismatch and lowered defect density. The resultant PVSC devices deliver a champion power conversion efficiency (PCE) of 25.07% with enhanced stability, and the unencapsulated PVSC device maintains 95% of its initial PCE after 1000 h of operation at the maximum power point under simulated AM 1.5G illumination.

In this work, we reveal the existence of a built-in potential at the homojunction interface of the perovskite film near the electron-transporting SnO2 layer. Adjusting the energy-level alignment at this interface is found to play a critical role in mitigating ion migration, which eventually enhances photovoltaic performance and stability.

Publication date: May 2024

Source: Nano Energy, Volume 123

Author(s): Mengqi Jin, Chong Chen, Fumin Li, Zhitao Shen, Hu Shen, Dong Yang, Huilin Li, Ying Liu, Chao Dong, Rong Liu, Mingtai Wang

Inverted perovskite solar cells (PSCs) have both excellent stability and continuously broken-through efficiencies. Herein, the characteristics of inverted PSCs including each functional layers, interfacial regulation strategies, and device stability are summarized. Meanwhile, the applications of inverted structure in tandem and flexible photovoltaic devices, and modules are introduced. Finally, the remaining challenges and several proposals of PSCs are put forward.

Abstract

Perovskite solar cells (PSCs) have attracted widespread research and commercialization attention because of their high power conversion efficiency (PCE) and low fabrication cost. The long-term stability of PSCs should satisfy industrial requirements for photovoltaic devices. Inverted PSCs with a p-i-n architecture exhibit considerable advantages because of their excellent stability and competitive efficiency. The continuously broken-through PCE of inverted PSCs shows huge application potential. This review summarizes the developments and outlines the characteristics of inverted PSCs including charge transport layers (CTLs), perovskite compositions, and interfacial regulation strategies. The latest effective CTLs, interfacial modification, and stability promotion strategies especially under light, thermal, and bias conditions are emphatically analyzed. Furthermore, the applications of the inverted structure in high-efficiency and stable tandem, flexible photovoltaic devices, and modules and their main obstacles are systematically introduced. Finally, the remaining challenges faced by inverted devices are discussed, and several directions for advancing inverted PSCs are proposed according to their development status and industrialization requirements.

An anti-solvent-free (ASF) technique is devised to fabricate photostable pure-iodide wide-bandgap perovskite solar cells (PSCs). Compared with wide-bandgap PSCs made from anti-solvent process, the ASF method significantly improves the device performance and reproducibility. Furthermore, methylammonium chloride is applied to enhance the crystallinity. Consequently, the ASF-based PSCs deliver a highest PCE of 21.30 % with excellent photostability.

Abstract

The perovskite/silicon tandem solar cell (TSC) has attracted tremendous attention due to its potential to breakthrough the theoretical efficiency set for single-junction solar cells. However, the perovskite solar cell (PSC) designed as its top component cell suffers from severe photo-induced halide segregation owing to its mixed-halide strategy for achieving desirable wide-bandgap (1.68 eV). Developing pure-iodide wide-bandgap perovskites is a promising route to fabricate photostable perovskite/silicon TSCs. Here, we report efficient and photostable pure-iodide wide-bandgap PSCs made from an anti-solvent-free (ASF) technique. The ASF process is achieved by mixing two precursor solutions, both of which are capable of depositing corresponding perovskite films without involving anti-solvent. The mixed solution finally forms Cs_0.3DMA_0.2MA_0.5PbI₃ perovskite film with a bandgap of 1.68 eV. Furthermore, methylammonium chloride additive is applied to enhance the crystallinity and reduce the trap density of perovskite films. As a result, the pure-iodide wide-bandgap PSC delivers efficiency as high as 21.30 % with excellent photostability, the highest for this type of solar cells. The ASF method significantly improves the device reproducibility as compared with devices made from other anti-solvent methods. Our findings provide a novel recipe to prepare efficient and photostable wide-bandgap PSCs.

Recent progress on the influence of pressure on perovskite materials and devices is reviewed. Based on the mechanism of influence, the pressure effect can be divided into six categories: crystal densification, crystal orientation, crystal size, bond length, bond angle, bandgap, phase transition, and amorphous phase. Finally, prospects for developing new perovskite structures and devices under pressure are presented.

Abstract

As a fundamental thermodynamic parameter, pressure serves as an effective tool to control the structures and properties of functional materials. To date, numerous pressure-engineering methods have been introduced to enhance perovskite structures and devices. This paper comprehensively reviews the advances in understanding the effects of pressure on perovskite materials and devices, encompassing both low and high-pressure influences. These effects are categorized into six distinct groups based on their underlying mechanisms, detailing the evolution of perovskite structures from macroscopic to microscopic levels, and exploring the interplay between these structures and their functional characteristics. Finally, the current challenges and offer insights into the future prospects for harnessing pressure effects to further develop perovskite structures, properties, and devices are assessed.

Py-DB with an extended conjugated structure is an effective dopant-free HTM when applied in n-i-p-type PSCs, affording an efficiency of 24.33 %, the highest PCE for a dopant-free small-molecule HTM.

Abstract

Dopant-free hole transporting materials (HTMs) is significant to the stability of perovskite solar cells (PSCs). Here, we developed a novel star-shape arylamine HTM, termed Py-DB, with a pyrene core and carbon-carbon double bonds as the bridge units. Compared to the reference HTM (termed Py-C), the extension of the planar conjugation backbone endows Py-DB with typical intermolecular π–π stacking interactions and excellent solubility, resulting in improved hole mobility and film morphology. In addition, the lower HOMO energy level of the Py-DB HTM provides efficient hole extraction with reduced energy loss at the perovskite/HTM interface. Consequently, an impressive power conversion efficiency (PCE) of 24.33 % was achieved for dopant-free Py-DB-based PSCs, which is the highest PCE for dopant-free small molecular HTMs in n-i-p configured PSCs. The dopant-free Py-DB-based device also exhibits improved long-term stability, retaining over 90 % of its initial efficiency after 1000 h exposure to 25 % humidity at 60 °C. These findings provide valuable insights and approaches for the further development of dopant-free HTMs for efficient and reliable PSCs.

Nature Communications, Published online: 05 March 2024; doi:10.1038/s41467-024-46145-7

The development of robust quasi-ohmic contact with minimal resistance, exceptional stability and cost-effectiveness is crucial for practical application of perovskite solar cells. Here, authors report a polymer-acid-metal structure as the contact and realize long photo-thermal-operational stability.

The application of self-assembled monolayer (SAMs) in perovskite solar cells has made the performance of p–i–n structure devices develop rapidly, while the relationship of function group, anchor groups, and spacers often is neglected. It is found that anchoring groups and spacers can affect the coordination between SAMs and perovskite. This work demonstrates different components of perovskites are selective to SAMs.

Abstract

Self-assembled monolayers (SAMs) have displayed great potential for improving efficiency and stability in p–i–n perovskite solar cells (PSCs). The anchoring of SAMs at the conductiv metal oxide substrates and their interaction with perovskite materials must be rationally tailored to ensure efficient charge carrier extraction and improved quality of the perovskite films. Herein, SAMs molecules with different anchoring groups and spacers to control the interaction with perovskite in the p–i–n mixed Sn–Pb PSCs are selected. It is found that the monolayer with the carboxylate group exhibits appropriate interaction and has a more favorable orientation and arrangement than that of the phosphate group. This results in reduced nonradiative recombination and enhanced crystallinity. In addition, the short chain length leads to an improved energy level alignment of SAMs with perovskite, improving hole extraction. As a result, the narrow bandgap (≈1.25 eV) Sn–Pb PSCs show efficiencies of up to 23.1% with an open-circuit voltage of up to 0.89 V. Unencapsulated devices retain 93% of their initial efficiency after storage in N₂ atmosphere for over 2500 h. Overall, this work highlights the underexplored potential of SAMs for perovskite photovoltaics and provides essential findings on the influence of their structural modification.

Indium ion (In³⁺) is introduced into the perovskite precursor solution to balance the interaction rate of SnI₂ and PbI₂ with organic salt. In³⁺ has a lower reduction potential compared to Sn²⁺, so it generates an extra energy barrier for Sn²⁺ oxidation. The optimal devices achieve a PCE of 23.34%, one of the highest PCEs for solar cells made by PCBM.

Abstract

Low-bandgap mixed tin (Sn)-lead (Pb) perovskite solar cells promise efficiency beyond the pure-Pb ones. However, the difference in the interaction rate of SnI₂ and PbI₂ with organic salts causes spatial distribution heterogeneity of Sn²⁺ and Pb²⁺ in mixed Sn─Pb perovskite layers. This causes a Sn-rich surface, which can trigger more severe Sn²⁺ oxidation and nonradiative recombination. A strategy, of introducing indium ion (In³⁺) into the perovskite precursor solution to compete with Sn²⁺ when reacting with organic salts is developed. Therefore, the nucleation and crystallization of perovskite films are well-controlled, leading to improved film quality with a more balanced Sn/Pb ratio on the film surface. Additionally, In³⁺ has a lower reduction potential compared to Sn²⁺ which can generate an extra energy barrier for Sn²⁺ oxidation. The improved film quality and reduced surface oxidation result in accelerated electron transfer and reduced carrier recombination rate. The modified devices achieve a power conversion efficiency (PCE) of 23.34%, representing one of the highest PCEs in mixed Sn─Pb solar cells made with PCBM.

This review breaks down the mechanisms of self-healing perovskite solar cells using polymeric additives from a bonding perspective. Functional groups such as isocyanate, disulfide, and carboxylic acid initiate the chemical interaction-based recovery of damaged perovskite devices, while hydrogen bonding and chelating groups facilitate physical interaction-based recovery. Additionally, perovskite's intrinsic properties enable mending autonomously under certain conditions.

Abstract

This review addresses the self-healing effects in perovskite solar cells (PSCs), emphasizing the significance of chemical and physical bonding as core mechanisms. Polymeric additives play a vital role in inducing self-healing phenomena along with the intrinsic properties of perovskite materials, both of which are discussed herein. As a relatively underexplored area, the self-healing effect induced by polymeric additives in PSCs is reviewed from a chemical perspective. The chemical bonds involved in self-healing include isocyanate, disulfide, and carboxylic acid groups. The physical bonds related to self-healing effects are primarily hydrogen bonding and chelation. Self-healing in flexible perovskite devices extends their lifespan and improves their mechanical robustness against environmental and mechanical stressors. This discussion delves into the initiation methods for self-healing, the conditions required, and the recovery-rate profiles. This review not only catalogs various approaches to self-healing, but also considers the fundamental limitations and potential of this phenomenon in PSCs. In addition, insights and an outlook on self-healing in perovskite-based optoelectronics are provided, offering guidance for future research and applications.

Nature Energy, Published online: 26 January 2024; doi:10.1038/s41560-024-01451-8

Oxidation of halides and subsequent segregation limit the stability of perovskite solar cells. Wu et al. synthesize anthraquinone derivatives to suppress oxidation while also passivating defects, achieving 25.2%-efficiency organic/perovskite tandem solar cells.

Compared with the conventional hole-transport layer used in inverted PSCs, hole-selective self-assembled monolayers provide multiple advantages, including conformal and uniform coating, minimized thickness, negligible optical and resistance loss, and the versatility in the interface modification.

Hole-transport layer (HTL) is of paramount importance to construct high-performance inverted perovskite solar cells (PSCs) because it not only determines the hole extraction and transport but also influences the quality of perovskite layer. Recently, self-assembled monolayers are adopted as very effective hole-selective layer to construct high-performance inverted PSCs. Compared with conventional HTL, hole-selective self-assembled monolayers (HSSAMs) offer the benefits of minimal material consumption and parasitic absorption, simple and scalable processing, and the versatility in the interface modification. Through molecule design and coating process optimization, the high-quality HSSAMs are obtained, which enable the HSSAM-based inverted PSCs to achieve greatly promoted photovoltaic performance. Herein, the progress of HSSAMs used in inverted PSCs is summarized. First, the structure characteristics of HSSAM molecules are described. Then, the effect of the structure of HSSAM molecules on their function in boosting the device performance and stability is discussed. Furthermore, the deposition strategies to form high-quality HSSAMs for inverted PSCs are analyzed. Finally, the advantages and challenges associated with application of HSSAMs in inverted PSCs are discussed, and the perspectives of the future research trends on HSSAMs for further promoting the performance of inverted PSCs are suggested.

An anion stabilization strategy is developed to simultaneously realize the excellent stability from precursor solution and films to final devices in the whole air preparation process. The influence of different anion species on the efficiency and stability of two-step deposited PSCs is comprehensively investigated and evaluated. Finally, TFSI-treated PSCs deliver an impressive efficiency of 24.16% with superior environmental and mechanical stability.

Abstract

Despite the outperforming power conversion efficiency of low-temperature and solution-processed perovskite solar cells (PSCs) realized over the past decades, the undesirable stability from precursor inks to resultant devices and harsh preparation requirements still restrain their industrial production and practical deployment. Herein, an anion stabilization strategy is developed to achieve the comprehensive durability of perovskite photovoltaics throughout the whole two-step air-processed procedure. The effect of interionic bonding strengths on the ink properties, film crystallization, and photovoltaic performances is in-depth explored and revealed. The pseudohalide bis(trifluoromethanesulfonyl)imide ions (TFSI⁻) not only improve the dispersion and stabilities of lead polyhalides and organic salt inks via strong electron-withdrawing/donating chemical sites, but also realize high composition uniformity and preferential crystal growth of subsequent deposited perovskite layers by tuning the precursor reactivity and surface absorption. Ultimately, the optimizing PSCs deliver a superior efficiency of 24.16%, accompanied by notably improved long-term stability toward extreme environmental and mechanical stimuli with lead leakage suppression. This work opens up a promising avenue toward reproducible air preparation of highly efficient, stable, and environmentally friendly perovskite optoelectronic devices via precise modulation of precursor properties.

An ionic liquid, named BMITFSI, assisted solution growth approach is proposed for fabricating high-quality perovskite single crystals with in situ self-cleaning effect, which not only gets rid of intricate post-treatments but also regulates preferential crystal facet growth, and thereby effectively ameliorates crystallographic defects for highly efficient perovskite single crystal-based photodetector application.

Abstract

Surface defects are crucial to perovskite single crystals (SCs) for versatile optoelectronic applications, whereas suffers from the intricate post-treatments and unsatisfactory reproducibility within solution growth strategy due to the residue solvent corrosion and adsorbed precursors deposition. Here, an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI) is demonstrated, assisted solution growth approach for fabricating high-quality self-cleaning perovskite single crystals with no need for any post-treatment. Benefiting from the in situ assembling in crystalline surface, BMITFSI can effectively decrease the crystallographic trap density by simultaneously introducing the self-cleaning effect and optimizing the crystalline growth process. Particularly, as fabricated MAPbI₃ single crystal exhibits an impressive photodetection performance with a specific detectivity of 2.83 × 10¹² Jones in visible-IR spectrum and a sensitivity of 7.24 × 10⁴ µC Gy_air ⁻¹ cm⁻² in X-ray detection, which is as good as the conventionally fabricated crystal with elaborate post-treatments. Based on the chemical composition independent universality, this work paves an easy but efficient route to improve the current crystallization methodology toward high-quality perovskite SCs fabrication.

This work develops an ultrafast nucleation process using MACl and BACl as dual additives to 2ME without further solvent addition and the FAPbI₃ PSCs achieve a higher efficiency of 23. 6% with compact and pinhole-free morphology.

Abstract

2-Methoxyethanol (2ME), as a more environmentally friendly solvent with a lower boiling point compared to dimethylformamide, is ideal for the fabrication of perovskite solar cells (PSCs). However, when 2ME is used for antisolvent-free deposition of perovskite films, an uncontrolled nucleation process and an easy phase transition to the δ-phase often occur. Herein, an ultrafast nucleation process is developed using methylamine chloride (MACl) and n-butylammonium chloride (BACl) as dual additives in 2ME without further solvent addition. While MACl can rapidly induce MACl-based nuclei to initiate the nucleation process for formamidinium lead iodide (FAPbI₃), the addition of BACl to the precursor with MACl can further increase the nucleation rate and density of nuclei, and bypass the transition from δ- to α-phase during crystal growth to obtain a highly crystalline and pinhole-free perovskite film. As a result, the FAPbI₃ PSCs achieve a power conversion efficiency (PCE) of 23.6%. This work provides a new inspiration for controlling the crystal quality of perovskite thin films via nucleation rate suitable for upscaling.

Publication date: April 2024

Source: Nano Energy, Volume 122

Author(s): Yucheng Li, Biao Shi, Qiaojing Xu, Lingling Yan, Ningyu Ren, Yuxiang Li, Wei Han, Zhao Zhu, Yubo Zhang, Jingjing Liu, Cong Sun, Sanlong Wang, Qian Huang, Dekun Zhang, Huizhi Ren, Xiaona Du, Ying Zhao, Xiaodan Zhang

Metal halide perovskites (MHPs) are outstanding photovoltaic materials. Nonetheless, despite significant progress, perovskite solar cells (PSCs) still face challenges. It is crucial to adjust the crystallization process during solution crystallization and film formation to overcome this challenge. We primarily discuss the relevant aspects of MHP crystallization kinetics, systematically summarize theoretical methods, and outline modulation techniques for MHP crystallization, including solution engineering, additive engineering, and component engineering.

Abstract

Metal halide perovskites (MHPs) are considered ideal photovoltaic materials due to their variable crystal material composition and excellent photoelectric properties. However, this variability in composition leads to complex crystallization processes in the manufacturing of Metal halide perovskite (MHP) thin films, resulting in reduced crystallinity and subsequent performance loss in the final device. Thus, understanding and controlling the crystallization dynamics of perovskite materials are essential for improving the stability and performance of PSCs (Perovskite Solar Cells). To investigate the impact of crystallization characteristics on the properties of MHP films and identify corresponding modulation strategies, we primarily discuss the relevant aspects of MHP crystallization kinetics, systematically summarize theoretical methods, and outline modulation techniques for MHP crystallization, including solution engineering, additive engineering, and component engineering, which helps highlight the prospects and current challenges in perovskite crystallization kinetics

Nature Energy, Published online: 18 January 2024; doi:10.1038/s41560-023-01444-z

Retaining high performance of perovskite solar cells over large areas is a challenge. Yang et al. use a thermotropic liquid crystal with high diffusivity that does not co-crystallize with the perovskite, suppressing defect formation and enabling large-area solar modules with improved stability and efficiency.