Crystallization Of Perovskite Films Research Articles

CO2 Laser Crystallization in Ambient for Highly Efficient FAPbI3 Perovskite Solar Cells.

Metal halide perovskite solar cells have achieved tremendous progress and have attracted enormous research and development efforts since the first report of demonstration in 2009. Due to fabrication versatility, many heat treatment methods can be utilized to achieve perovskite film crystallization. Herein, 10.6µm carbon dioxide laser process is successfully developed for the first time for perovskite film crystallization. In addition, this is the first time formamidinium lead triiodide solar cells by laser annealing under ambient are demonstrated. The champion cell produces a power conversion efficiency of 21.8%, the highest for laser-annealed perovskite cells. And this is achieved without any additive, passivation, or post-treatment.

Controlling Water for Enhanced Homogeneities in Perovskite Solar Cells with Remarkable Reproducibility

AbstractTwo‐step sequential deposition of perovskite films is proven efficient and compatible with large‐scale production. Nevertheless, its critically regulated environmental humidity often remains a burden, hindering its applications in reproducible fabrication of perovskite solar cells (PSCs). Herein, by introducing a water ethyl acetate (W‐EA) solution treatment before annealing, improved perovskite crystallinity and homogeneity in FA0.95‐xMAxCs0.05PbI3 films without additional composition regulation is achieved. In situ Grazing‐incidence Wide‐angle X‐ray Scattering experiments highlighted accelerated crystallization kinetics in W‐EA‐treated films, leading to high‐quality perovskite formation. PSCs based on this method reached an optimal power conversion efficiency of 25.01% and demonstrated enhanced moisture resistance, retaining 88% efficiency after 1000 h in ambient conditions. This W‐EA treatment simplifies the fabrication process, greatly reducing the need for controlled humidity, and offers insights into the role of water in perovskite film crystallization, with significant implications to produce high‐performance PSCs.

Designed Additive to Regulated Crystallization for High Performance Perovskite Solar Cell

AbstractIt is a crucial role for enhancing the power conversion efficiency (PCE) of perovskite solar cells (PSCs) to prepare high‐quality perovskite films, which can be achieved by delaying the crystallization of perovskite film. Hence, we designed difluoroacetic anhydride (DFA) as an additive to regulating crystallization process thus reducing defect formation during perovskite film formation. It was found DFA reacts with DMSO by forming two molecules, difluoroacetate thioether ester (DTE) and difluoroacetic acid (DA). The strong bonding DTE⋅PbI2 and DA⋅PbI2 retard perovskite crystallization process for high‐quality film formation, which was monitored through in situ UV/Vis and PL tests. By using DFA additives, we prepared perovskite films with high‐quality and low defects. Finally, a champion PCE of 25.28 % was achieved with excellent environmental stability, which retained 95.75 % of the initial PCE after 1152 h at 25 °C under 25 % RH.

Designed Additive to Regulated Crystallization for High Performance Perovskite Solar Cell.

It is a crucial role for enhancing the power conversion efficiency (PCE) of perovskite solar cells (PSCs) to prepare high-quality perovskite films, which can be achieved by delaying the crystallization of perovskite film. Hence, we designed difluoroacetic anhydride (DFA) as an additive to regulating crystallization process thus reducing defect formation during perovskite film formation. It was found DFA reacts with DMSO by forming two molecules, difluoroacetate thioether ester (DTE) and difluoroacetic acid (DA). The strong bonding DTE⋅PbI2 and DA⋅PbI2 retard perovskite crystallization process for high-quality film formation, which was monitored through in situ UV/Vis and PL tests. By using DFA additives, we prepared perovskite films with high-quality and low defects. Finally, a champion PCE of 25.28 % was achieved with excellent environmental stability, which retained 95.75 % of the initial PCE after 1152 h at 25 °C under 25 % RH.

Multiple Stabilization Effects of Benzylhydrazine on Scalable Perovskite Precursor Inks for Improved Perovskite Solar Cell Production.

Perovskite precursor inks suffer various forms of degradation, such as iodide anion oxidation and organic cation breakdown, hindering reliable perovskite solar cell manufacturing. Here we report that benzylhydrazine hydrochloride (BHC) not only retards the buildup of iodine as previously reported but also prevents the breakdown of organic cations. Through investigating BHC and iodine chemical reactions, we elucidate protonation and dehydration mechanisms, converting BHC to harmless volatile compounds, thus preserving perovskite film crystallization and solar cell performance. This inhibition effect lasts nearly a month with minimal BHC, contrasting control inks without BHC where organic cations fully react in less than a week. This enhanced understanding, from additive stabilization to end products, promises improved perovskite solar cell production reliability.

An Equalized Flow Velocity Strategy for Perovskite Colloidal Particles in Flexible Perovskite Solar Cells.

The non-uniform distribution of colloidal particles in perovskite precursor results in an imbalanced response to the shear force during flexible printing process. Herein, it is observed that the continuous disordered migration occurring in perovskite inks significantly contributes to the enlargement of colloidal particles size and diminishes the crystallization activity of the inks. Therefore, a molecular encapsulation architecture by glycerol monostearate to mitigate colloidal particles collisions in the precursor ink, while simultaneously homogenizing the size distribution of perovskite colloids to minimize their diffusion disparities, is devised. The utilization of colloidal particles with a molecular encapsulation structure enables the achievement of uniform deposition during the printing process, thereby effectively balancing the crystallization rate and phase transition in the film and facilitating homogeneous crystallization of perovskite films. The large-area flexible perovskite device (1.01 cm2 and 100 cm2) fabricated through printing processes, achieves an efficiency of 24.45% and 15.87%, respectively, and manifests superior environmental stability, maintaining an initial efficiency of 91% after being stored in atmospheric ambiences for 150 days (unencapsulated). This work demonstrates that the dynamic evolution process of colloidal particles in both the precursor ink and printing process represents a crucial stride toward achieving uniform crystallization of perovskite films.

Bridging the buried interface with conjugated molecule for highly efficient carbon-based inorganic CsPbI2Br perovskite solar cells fabricated in air

Manipulating the buried interface of all-inorganic perovskite solar cells (PSCs) is essential to improve the performance of devices. However, the conventional modifiers of interface typically present insulating feature that can impede the transportation of carrier, leading to an inferior charge transport efficiency. Herein, we propose a conjugated molecule, 2,4-hexadienoic acid potassium salt, which can act as a bridge at the buried interface of device and improve the crystallization of perovskite film. Besides, this interfacial modifier also promotes larger and denser grains, passivating defects and suppress non-radiative recombination of buried interface. Simultaneously, the electrical performance of tin oxide film is enhanced and facilitate a better energy level alignment. Consequently, carbon electrodes-based PSCs (C-PSCs) are fabricated via a hot air-assisted method in air, and C-PSCs based on all-inorganic perovskite demonstrate significant enhancement of open circuit voltage (1.25 V) via conjugated molecule modification, and the power conversion efficiency (PCE) increase significantly from 10.86 % to 13.11 %. Moreover, unencapsulated target devices exhibit better stability than the control devices. This work offers a new idea to construct an interfacial bridge via conjugated molecule for efficient and stable C-PSCs fabricated in air.

Highly ordered crystallization of α-FAPbI3 films via homogeneous seeds for efficient perovskite solar cells

Formamidine lead triiodide (FAPbI3) perovskites have become the most promising photovoltaic materials for perovskite solar cells with record power conversion efficiency (PCE). However, random nucleation, phase transition, and lattice defects are still the key challenges limiting the quality of FAPbI3 films. Previous studies show that the introduction or adding of seeds in the precursor is effective to promote the nucleation and crystallization of perovskite films. Nevertheless, the seed-assisted approach focuses on heterogeneous seeds or hetero-composites, which inevitably induce a lattice-mismatch, the generation of strain or defects, and the phase segregation in the perovskite films. Herein, we first demonstrate that high-quality perovskite films are controllably prepared using α- and δ-phases mixed FAPbI3 microcrystal as the homogeneous seeds with the one-step antisolvent method. The partially dissolved seeds with suitable sizes improve the crystallinity of the perovskite film with preferable orientation, improved carrier lifetime, and increased carrier mobility. More importantly, the α-phase-containing seeds promote the formation of α-phase FAPbI3 films, leading to the reduction of residual lattice strain and the suppression of I− ion migration. Besides, the adding of dimethyl 2,6-pyridine dicarboxylate (DPD) into the precursor further suppresses the generation of defects, contributing to the PCE of devices prepared in air ambient being significantly improved to 23.75%, among the highest PCEs for fully air-processed FAPbI3 solar cells. The unpackaged target devices possess a high stability, maintaining 80% of the initial PCE under simulated solar illumination exceeding 800 h.

Triple Cross-Linking Engineering Strategies for Efficient and Stable Inverted Flexible Perovskite Solar Cells.

Inverted flexible perovskite solar cells (fPSCs) are promising for commercialization due to their low cost, lightweight, and excellent stability. However, enhancing fPSCs' power conversion efficiency and stability remains challenging. Here, an unprecedented triple cross-linking engineering strategy is innovatively exhibit for efficient and stable inverted fPSCs. First, a carefully designed cross-linker, 4-fluorophenyl 5-(1,2-dithiolan-3-yl) pentanoate (FB-TA), is added to the perovskite precursor solution. During the perovskite film's crystallization at a low temperature, the cross-linking product of FB-TA can passivate the grain boundaries and reduce the film's residual strain and Young's module. Then, FB-TA is also introduced for the bottom- and top-interface modification of the perovskite film. The interfacial treating strategy protects the perovskite from water invasion and strengthens the interfaces. The combination of triple strategies affords highly efficient inverted fPSCs with a champion efficiency of 21.42% among the state-of-the-art inverted fPSCs based on nickel oxides. More importantly, the flexible devices also exhibit superior stabilities with T90 >4000 bending cycles, photostability with T90 >568h, and ambient stability with T90 >2000h, especially the stability with T80 >1120h under harsh damp-heat conditions (i.e., 85°C and 85% RH). The strategy provides new insights into the industrialization of high-performance and stable fPSCs.

Dimethylamine oxalate manipulating CsPbI3 perovskite film crystallization process for high efficiency carbon electrode based perovskite solar cells

Crystallization process determines the quality of perovskite films and the performances of resultant perovskite solar cells (PSCs). Dimethylamine oxalate has been proven as a multifunctional modulator, and is explored as an efficient additive in manipulating the crystallization process of CsPbI3 perovskite films. On one hand, oxalate serves as the precipitator that facilitates the nucleation process of intermediate. The larger size of intermediate is conductive to the larger size and smaller grain boundaries of resultant perovskite. On the other hand, in subsequent annealing process, the phase conversion and growth process of transient perovskite can be decelerated due to the strong interactions of oxalate with both dimethylamine cation (DMA+) and Pb2+. Due to the optimized crystallization kinetics, the morphology and quality of CsPbI3 perovskite films are comprehensively improved with lower defect concentrations, and charge recombination loss is effectively suppressed. Benefiting from the optimized crystal quality of perovskite films, the carbon electrode-based CsPbI3 PSCs exhibit a champion efficiency of 18.48%. This represents one of the highest levels among all hole transport layer-free inorganic perovskite solar cells.

Indium Iodide Additive Realizing Efficient Mixed Sn─Pb Perovskite Solar Cells

AbstractLow‐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.

Diffusion-Controlled Crystal Engineering with Diverse Antisolvent Intervention for the Preparation of High-Quality Hybrid Perovskite Films.

Antisolvent engineering is routinely used to modulate the crystallization of perovskite films as they can offer an additional driving force for nucleation. Actually, the intervention of antisolvent into nucleation is thought to involve some relatively fast and complex processes, which, however, are not fully understood so far. Here, the diffusion of the organic amine cation FA+ (one dominated precursor) and its distribution in a spin-coating process in different antisolvents is simulated by the computational fluid dynamics (CFD) model. It is suggested that a moderate diffusion rate (like that in the case of toluene as an antisolvent) not only enables to form a very uniform distribution of FA+ ions on the substrate, beneficial to the uniform nucleation of the intermediate phase, but also can balance the nucleation and growth rates of the intermediate phase, thereby suppressing undesired heterogeneous nucleation and growth. Results show that the perovskite film fabricated using toluene as an antisolvent has a high quality, based on which higher power conversion efficiencies of up to 24.32% are achieved for perovskite solar cells.

Perovskite Crystallization Regulation via Antimonene Quantum Sheets for Highly Efficient and Stable Solar Cells.

The two-step deposition method offers significant advantages in the production of high-performance planar perovskite solar cells (PSCs). Nevertheless, there are still numerous challenges in regulating perovskite crystallization during the two-step process. In this work, two-dimensional (2D) material antimonene quantum sheets (AMQSs) as an additive are introduced to regulate the crystallization process of perovskite. As a result, perovskite films with high crystalline quality and vertical growth orientation are obtained by AMQSs providing heterogeneous nucleation sites with the penetration of a mixture solution of AMQSs and FAI into the PbI2 layer. Also, the influence mechanism of AMQSs on the crystallization of perovskite film is analyzed in details. At the same time, due to the chemical interaction between antimonene and the uncoordinated Pb2+, the defects in the perovskite are efficiently passivated. In addition, the energy level at the perovskite/SnO2 interface becomes more matched, leading to improved charge transport and extraction with the incorporation of AMQSs. Benefiting from the versatile AMQSs, the power conversion efficiency (PCE) of PSCs made by PbI2 + FAI:AMQSs is improved from 20.65 to 22.31% with the vastly enhanced Jsc and Voc. The ambient and operational stability of the unencapsulated PSCs fabricated using the PbI2 + FAI:AMQSs method were significantly improved, retaining 80% of the original PCE after being stored in a dark environment at a relative humidity of 30-40% for 18 days and 83% of the original PCE following continuous AM 1.5G illumination for 200 h.

2D BA2PbI4 Regulating PbI2 Crystallization to Induce Perovskite Growth for Efficient Solar Cells.

Using seeds to control the crystallization of perovskite film is an effective strategy for achieving high-efficiency perovskite solar cells (PSCs). Owing to their excellent environmental stability brought by their long alkyl chain, n-butylammonium (BA) cations are widely used for fabricating efficient and stable PSCs. However, BA-based 2D perovskite is seldom been investigated as a seed. Here, BA2PbI4 is employed to regulate the crystallization of PbI2, acting as nucleation centers. As a result, porous PbI2 film with high crystallinity is obtained, which allows the realization of perovskite film with preferential crystal orientations of (001) and large grain size of over 2µm. The corresponding PSC achieves a high power conversion efficiency (PCE) of 24.30% and exhibits satisfactory stability, retaining 91.70% of the initial PCE after 300h of thermal aging at 85°C.

Au Nanocluster Assisted Microstructural Reconstruction for Buried Interface Healing for Enhanced Perovskite Solar Cell Performance.

The heterogeneity of perovskite film crystallization along the vertical direction leads to voids and traps at the buried interfaces, hampering both efficiency and stability of perovskite solar cells. Here, bovine serum albumin-functionalized Au nanoclusters (ABSA), combined with heavy gravity, high surface charge density, and strong interactions with the electron transport layer, are designed to reconstruct the buried interfaces for not only high-quality crystallization, but also improved carrier transfer. The ABSA macromolecules with amine function groups and larger surface charge density interact with the perovskite to improve the crystallinity, and gradually migrate towards the buried interface, healing the defective voids, hence suppressing surface recombination velocity from 3075 to 452 cm s-1 . The healed buried interface and the higher surface potential of ABSA-modified TiO2 lead to improved carrier extraction at the interface. The resulting solar cell attains a power conversion efficiency of 25.0% with negligible hysteresis and remarkable stability, maintaining 92.9% of their initial efficiency after 3200 h of exposure to the ambient atmosphere, they also exhibit better continuous irradiation stability compared to control devices. These findings provide a new metal-protein complex to eliminate the deleterious voids and defects at the buried interface for improved photovoltaic performance and stability.

Improved Efficiency and Stability of Perovskite Solar Cells by Binary Perovskite–Organic Composite Thin Film

Regulating perovskite film crystallization and avoiding bulk defects during the deposition process are essential for achieving perovskite solar cells (PSCs) with excellent power conversion efficiency (PCE) and stability. Herein, the synergistic effects between n‐type, narrow‐bandgap conjugated organic molecules (2,2′‐((2Z,2′Z)‐((5,5′‐(4,4,9,9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydros‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐5,2‐diyl))bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile [IEICO]) and perovskites on film surface morphology and stability, and the regulation mechanism on bulk defects in MAPb(I0.97Br0.03)3:IEICO films are explored. The results of theoretical and experimental studies indicate that a large number of electrons on the CO and C≡N surface functional groups of IEICO can function as Lewis bases and exhibit strong interactions with uncoordinated Pb2+ ions, substantially reducing bulk defects. Moreover, the resulting MAPb(I0.97Br0.03)3:IEICO film exhibits an optical response in the near‐infrared region and an increased crystallite size. Consequently, the MAPb(I0.97Br0.03)3:IEICO PSCs with a p–i–n device structure demonstrate a PCE exceeding 20%. In addition, the MAPb(I0.97Br0.03)3:IEICO PSCs possess superior stability and negligible photocurrent hysteresis. These results suggest that the incorporation of near‐infrared organic molecules into perovskites provides a simple method to achieve high‐performance PSCs and realize the utilization of near‐infrared wavelengths.

Bandgap Engineering of Two‐Step Processed Perovskite Top Cells for Perovskite‐Based Tandem Photovoltaics

AbstractFor high‐performance application of perovskite solar cells (PSCs) in monolithic perovskite/silicon tandem configuration, an optimal bandgap and process method of the perovskite top cell is required. While the two‐step method leads to regular perovskite film crystallization, engineering wider bandgaps (Eg > 1.65 eV) for the solution‐based two‐step method remains a challenge. This work introduces an effective and facile strategy to increase the bandgap of two‐step solution‐processed perovskite films by incorporating bromide in both deposition steps, the inorganic precursor deposition (step 1, PbBr2) and the organic precursor deposition (step 2, FABr). This strategy yields improved charge carrier extraction and quasi‐Fermi level splitting with power conversion efficiencies (PCEs) of up to 15.9%. Further improvements are achieved by introducing CsI in the bulk and utilizing LiF as surface passivation, resulting in a stable power output exceeding 18.5% for Eg = 1.68 eV. This additional performance boost arises from enhanced perovskite film crystallization, leading to improved charge carrier extraction. Laboratory scale monolithic perovskite/silicon solar cells (TSCs) (1 cm2 active area) achieve PCEs up to 23.7%. This work marks a significant advancement for wide bandgap two‐step solution‐processed perovskite films, enabling their effective use in high‐performance and reproducible PSCs and perovskite/silicon TSCs.

Aging‐Resistant Precursor with Ultrawide Annealing Window for 24.08% Perovskite Solar Cells

AbstractPerovskite solar cells (PSCs) have attracted extensive attention in the photovoltaic field, with their highest power conversion efficiency (PCE) reaching 26%. However, the commercialization of PSCs is severely hindered by the instability of precursor solutions and the narrow annealing window for perovskite films. Here, 2,3,5‐trichlorobenzaldehyde (3Cl‐BZH) is introduced into the organic salt precursor solution to eliminate excess organic amines through Schiff‐base reactions, avoiding subsequent irreversible amine‐cation reaction of formamidine‐methylammonium (FA‐MA+) and improve the stability of the precursor solution. Meanwhile, the chemical interaction between C═O group of 3Cl‐BZH and formamidinium (FA+) in the perovskite precursor contributes to the slow release of organic ions, which reduces the reaction rate between organic salt and PbI2, retarding the crystallization of perovskite film. The PSCs with a conventional annealing process achieve a champion efficiency of 24.08%, which derives from the defect passivation effect of 3Cl‐BZH. The PSCs with an ultrawide annealing window of 240 h for wet perovskite film in the air still maintain an efficiency of 22.01%. The aging‐resistant precursor and ultrawide annealing window are beneficial for reproducible, efficient, and low‐cost PSCs, which brings great prospects for the commercialization of PSCs.

Covalent organic frameworks for modulating crystallization kinetics in perovskite photovoltaics

Covalent organic frameworks (COFs), recognized for their conjugated frameworks, adjustable porosity, and customizable functionalization, are emerging as versatile materials in perovskite photovoltaics with the potential to enhance both device performance and stability. However, a comprehensive understanding of their precise influence on the intricate phenomenon of perovskite crystallization kinetics is still lacking. In this study, we have successfully synthesized two distinctive COF materials, namely HIAM-0001 and HIAM-0004, utilizing the structural units of 5′,5″″-(benzo[c] [1,2,5]thiadiazole-4,7-diyl)bis(([1,1′:3′,1″-terphenyl]-4,4″-dicarbaldehyde)) (BT-TDA), with either the additional unit p-xylylenedicyanide (PDAN) or 2,2′-([2,2′-bipyridine]-5,5′-diyl) diacetonitrile (BPyDAN). By incorporating them into the PbI2 layer, we have facilitated high-quality perovskite film fabrication through a two-step process. The COF-assisted PbI2 films exhibited a distinct porous structure, facilitating organic salt solution permeation and reducing PbI2 residues. Notably, in-situ UV–vis absorption characterization revealed slowed perovskite film crystallization kinetics with COF assistance, leading to the formation of larger crystal grains, fewer grain boundaries, reduced defect density, and suppressed non-radiative recombination, ultimately resulting in improved device performance. In comparison to HIAM-0001, the enhanced π-π interactions of HIAM-0004, with its bipyridine-based unit, exhibited more pronounced interactions with the perovskite, contributing to a remarkable PCE of 24.06% and excellent device stability. This study underscores the pivotal role of COF modification in shaping perovskite film crystallization kinetics, thereby enhancing film quality, reducing defects, and boosting device stability.

Recent Advances in Quality Strengthening of Perovskite Films by Additive Engineering for Efficient Solar Cells

In the past decade, perovskite solar cells (PSCs), exhibiting high efficiency, low cost, and flexibility, have made inspiring signs of progress and show great potential in large‐scale commercialization as representative third‐generation photovoltaic technology. Nevertheless, due to rapid crystallization of perovskite crystals through the solution film‐forming technique, a primary challenge is the fabrication of excellent perovskite films with superior optoelectronic characteristics and good flexibility. However, the defects and lattice stresses generated in the perovskite layer during rapid crystallization might diminish the efficiency, robustness, and reliability of PSCs. To date, a variety of techniques are being identified for strengthening the quality of perovskite films, which include interfacial engineering, solvent engineering, doping, and additives engineering. Among these strategies, developing effective additives is of utmost importance in controlling the kinetics of perovskite film crystallization, leading to improved device performance and mechanical stability, especially for flexible PSCs (FPSCs). Herein, the state‐of‐the‐art additives developed in PSCs during the past few years are retrospected, such as ionic liquids, polymers, and small organic molecules, and particular attention is paid to the advanced progress of additive engineering in FPSCs. Moreover, critical perspectives are put forward on the opportunities and challenges of additive engineering in the future development of PSCs.