Rationally Tailoring Chiral Molecules to Minimize Interfacial Energy Loss Enables Efficient and Stable Perovskite Solar Cells Using Vacuum Flash Technology

Functional Group Engineering Stabilizing Precursor Solution and Passivating Defects for Operationally Stable and Highly Reproducible Inverted Perovskite Solar Cells

The instability of perovskite precursor solution induced by deprotonation of organic cations and oxidation of iodide ions substantially deteriorates the reproducibility and reliability of the photovoltaic performance of perovskite solar cells (PSCs). The above decomposition reactions can be conquered via the synergistic engineering of organic functional groups. However, how spatial conformation and type of weak acid functional groups impact the stability of perovskite precursor solution remains to be investigated. Herein, it is uncovered that the position of functional groups on the benzene and the type of weak acid functional groups remarkably influence the acid dissociation constant (pKa) and thus the stability of perovskite inks. The pKa plays a decisive role in suppressing the deprotonation of organic cations and following the amine-cation addition-elimination reaction. The 4-hydrazinobenzenesulfonic acid (4-HBSA) with the lowest pKa is optimal in stabilizing perovskite inks and mitigating nonradiative recombination through defect passivation. This breakthrough enables the inverted PSCs to deliver a power conversion efficiency (PCE) of 26.79% (certified 26.36%, the highest PCE value for PSCs prepared in ambient conditions) using vacuum flash evaporation technology. The modulated PSC could maintain 92% of its initial efficiency after 2000 h of continuous maximum power point tracking.

Perovskite Crystallization Regulation by a Green Antisolvent for High-Performance NiOx-Based Inverted Solar Cells

Environmentally friendly antisolvents are key to achieving efficient, reproducible, and sustainable perovskite solar cells (PSCs). Here, a comparison was made between the traditional highly toxic chlorobenzene (CB) antisolvent and green antisolvents ethyl acetate (EA) and dimethyl carbonate (DMC). The employment of green antisolvent DMC was shown to result in the formation of perovskite films with enhanced grain size and superior crystal quality. This leads to an optimal energy level alignment with the electron transport layer, effectively mitigating the nonradiative recombination caused by film imperfections, reducing the loss of organic components during the annealing process, and suppressing the formation of the lead iodide phase. Finally, the champion device, based on the antisolvent DMC, exhibited a high power conversion efficiency (PCE) of 25.18%, which is one of the high PCEs reported for this device structure. Moreover, the device maintains 92% of its original PCE after approximately 1000 h under environmental conditions.

Rationally designed universal passivator for high-performance single-junction and tandem perovskite solar cells

Interfacial trap-assisted nonradiative recombination hampers the development of metal halide perovskite solar cells (PSCs). Herein, we report a rationally designed universal passivator to realize highly efficient and stable single junction and tandem PSCs. Multiple defects are simultaneously passivated by the synergistic effect of anion and cation. Moreover, the defect healing effect is precisely modulated by carefully controlling the number of hydrogen atoms on cations and steric hindrance. Due to minimized interfacial energy loss, L-valine benzyl ester p-toluenesulfonate (VBETS) modified inverted PSCs deliver a power conversion efficiency (PCE) of 26.28% using vacuum flash processing technology. Moreover, by suppressing carrier recombination, the large-area modules with an aperture area of 32.144 cm2 and perovskite/Si tandem solar cells coupled with VBETS passivation deliver a PCE of 21.00% and 30.98%, respectively. This work highlights the critical role of the number of hydrogen atoms and steric hindrance in designing molecular modulators to advance the PCE and stability of PSCs.

Synergistic Modulation of Orientation and Steric Hindrance Induced by Alkyl Chain Length in Ammonium Salt Passivator Toward High-performance Inverted Perovskite Solar Cells and Modules

Organic ammonium salts are extensively utilized for passivating surface defects in perovskite films to mitigate trap-assisted nonradiative recombination. However, the influence of alkyl chain length on the molecular orientation and spatial steric hindrance of ammonium salt remains underexplored, hindering advancements in more effective passivators. Here, a series of organic ammonium salts is reported with varying alkyl chain lengths to passivate surface defects and optimize band alignment. It is revealed that long alkyl chains promote parallel molecular orientation on the perovskite surface, thereby reinforcing interaction with surface defects, whereas excessive chain length introduces steric hindrance, weakening anion-perovskite interactions. Nonylammonium acetate (NAAc) with optimal chain length achieves the ideal balance between chemical interactions, resulting in superior passivation. Through NAAc passivation, high-performance inverted perovskite solar cells (PSCs) and modules are achieved, with power conversion efficiencies (PCE) of 25.79% (certified 25.12%) and 19.62%, respectively. This marks a record PCE for inverted PSCs utilizing vacuum flash technology in ambient conditions. Additionally, the NAAc-passivated devices retain 91% of their initial PCE after 1200 h of continuous maximum power point operation. This work offers new insights into the interplay between molecular orientation and steric hindrance, advancing the design of high-performance PSCs.

Single-Crystal Perovskite for Solar Cell Applications

The advent of organic-inorganic hybrid metal halide perovskites has revolutionized photovoltaics, with polycrystalline thin films reaching over 26% efficiency and single-crystal perovskite solar cells (IC-PSCs) demonstrating ≈24%. However, research on single-crystal perovskites remains limited, leaving a crucial gap in optimizing solar energy conversion. Unlike polycrystalline films, which suffer from high defect densities and instability, single-crystal perovskites offer minimal defects, extended carrier lifetimes, and longer diffusion lengths, making them ideal for high-performance optoelectronics and essential for understanding perovskite material behavior. This review explores the advancements and potential of IC-PSCs, focusing on their superior efficiency, stability, and role in overcoming the limitations of polycrystalline counterparts. It covers device architecture, material composition, preparation methodologies, and recent breakthroughs, emphasizing the importance of further research to propel IC-PSCs toward commercial viability and future dominance in photovoltaic technology.

Managing Pb-Related Imperfections via Rationally Designed Aniline Derivative with Bilateral Cyano and Acetyl Groups as Lewis Base for High-Efficiency Perovskite Solar Cells Exceeding 24

Pb-related imperfections (surface or halide vacancy induced uncoordinated Pb2+, Pb-I antisite, and Pb2+ vacancy defects) of the ionic crystal perovskite film seriously restrict the photovoltaic performance of perovskite solar cells (PSCs). Here, an aniline derivative N-(4-cyanophenyl)acetamide (CAL) is rationally designed, incorporating bilateral functional sites of cyano and acetyl groups, acting as Lewis base molecule for managing the Pb-related imperfections in perovskite surface through post-treatment. Theoretical calculation and experimental verification together proved the reduced defect density, improved crystallinity, and inhibited ion migration in the CAL-modified perovskite. Precisely, cyano as a side group and acetyl as another side group can both coordinate with Pb2+ for its low electrostatic potential energy. Further, the aniline core and the π-π conjugate structure in the benzene ring of the ligand tend to form a dimer to improve the mobility for carrier transportation and collection. The strategy demonstrates a champion PCE of 24.35% for the air-processed PSCs with over 1200 hours of maximum power point tracking (MPPT) stability. This study presents a comprehensive approach to overcoming the current Pb-related imperfections induced limitations in PSCs, paving the way for their integration into mainstream solar technologies.

Efficient Tin-Lead Perovskite Solar Cells with a Ultrawide Usage Windows of Precursor Solution Opened by SnF2

High quality tin-lead perovskite solar cells (Sn─Pb PSCs) can be fabricated via simple solution processing methods. However, the instability of precursor solutions and their narrow usage windows still pose challenges in manufacturing efficient and reproducible Sn─Pb PSCs, hindering the commercialization of PSCs. Fluorine tin (SnF2) is widely used as an antioxidant to improve the crystallinity of perovskite. In this study, another role of SnF2 as a stabilizer is found to restrain the deprotonation of methylammonium iodide (MAI) in the precursor solution, which improves their stability and expands their usage windows. Due to the inhibition of SnF2 on oxidation and deprotonation, stable large-sized colloidal clusters form gradually in perovskite precursor solution during aging, leading to uniform nucleation/crystallization during film growth, significantly reducing the roughness and defect density in the films. Because of the competitive deprotonation and oxidation process of Sn2+, the benefit of larger cluster maximizes after about ten days storage of precursor solution. The champion efficiency of Sn─Pb PSCs prepared with 10 days aged precursor solution is 22.00%. High performance of devices fabricated with precursor solution stored for even ≈40 days discloses the wide usage windows of precursor solution with SnF2 additive.

Synchronous Regulation Strategy of Pyrrolidinium Thiocyanate Enables Efficient Perovskite Solar Cells and Self-Powered Photodetectors

Developing inventive approaches to control crystallization and suppress trap defects in perovskite films is crucial for achieving efficient perovskite photovoltaics. Here, a synchronous regulation strategy is developed that involves the infusion of a zwitterionic ionic liquid additive, pyrrolidinium thiocyanate (PySCN), into the perovskite precursor to optimize the subsequent crystallization and defects. PySCN modification not only orchestrates the crystallization process but also deftly addresses trap defects in perovskite films. Within this, SCN- compensates for positively charged defects, while Py+ plays the role of passivating negatively charged defects. Based on the vacuum flash evaporation without anti-solvent, the air-processed perovskite solar cells (PSCs) with PySCN modification can achieve an extraordinary champion efficiency of 22.46% (0.1 cm2) and 21.15% (1.0 cm2) with exceptional stability surpassing 1200 h. Further, the self-powered photodetector goes above and beyond, showcasing an ultra-low dark current of 2.13 × 10-10 A·cm-2, a specific detection rate of 6.12 × 1013 Jones, and an expansive linear dynamic range reaching an astonishing 122.49 dB. PySCN modification not only signifies high efficiency but also ushers in a new era for crystallization regulation, promising a transformative impact on the optoelectronic performance of perovskite-based devices.