Tailored Cysteine‐Derived Molecular Structures toward Efficient and Stable Inorganic Perovskite Solar Cells

• Published in: Advanced materials (Weinheim) Vol. 35; no. 31; pp. e2301140 - n/a
• Main Authors: Zhang, Hao, Tian, Qingwen, Xiang, Wanchun, Du, Yachao, Wang, Zhiteng, Liu, Yali, Liu, Lidan, Yang, Tengteng, Wu, Haifeng, Nie, Ting, Huang, Wenliang, Najar, Adel, Liu, Shengzhong (Frank)
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.08.2023
• Subjects: all‐inorganic perovskite solar cells; Benzene; CsPbI3–xBrx; Cysteine; defect passivation; Electron density; Functional groups; Hydrophobicity; Materials science; Metal halides; Moisture effects; molecular design; Molecular structure; Perovskites; Photovoltaic cells; Solar cells; Thermal stability; molecular design; all-inorganic perovskite solar cells; cysteine; CsPbI3-xBrx; defect passivation
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202301140

Surface–defect‐triggered non‐radiative charge recombination and poor stability have become the main roadblock to continued improvement in inorganic perovskite solar cells (PSCs). Herein, the main culprits are identified on the inorganic perovskite surface by first‐principles calculations, and to purposefully design a brand‐new passivator, Boc‐S‐4‐methoxy‐benzyl‐l‐cysteine (BMBC), whose multiple Lewis‐based functional groups (NH, S and CO) to suppress halide vacancies and coordinate with undercoordinated Pb2+ through typical Lewis baseacid reactions. The tailored electron‐donating methoxyl group (CH3O–) can cause an increased electron density on the benzene ring, which strengthens the interaction with undercoordinated Pb2+ via electrostatic interactions. This BMBC passivation can reduce the surface trap density, enlarge grains, prolong the charge lifetime, and cause a more suitable energy‐level alignment. In addition, the hydrophobic tert‐butyl in butoxycarbonyl (Boc‐) group ensures that BMBC is uniformly covered and prevents harmful aggregation through steric repulsion at the perovskite/hole–transporting layer (HTL) interface, thus providing a hydrophobic umbrella to resist moisture invasion. Consequently, the combination of the above increases the efficiency of CsPbI3−xBrx PSC from 18.6% to 21.8%, the highest efficiency for this type of inorganic metal halide PSCs so far, as far as it is known. Moreover, the device exhibits higher environmental and thermal stability. A brand‐new passivator, Boc‐S‐4‐methoxy‐benzyl‐l‐cysteine (BMBC), is demonstrated to post‐treat CsPbI3−xBrx perovskite films. The synergistic effects of an energetic electron donor group and multiple Lewis‐based functional groups in BMBC are purposefully designed to passivate majority of defects. Benefiting from a hydrophobic tert‐butyl group in BMBC, the protection against water invasion is thus significantly enhanced. This study provides a useful understanding and rational design regarding the influence of the molecular configuration on the passivation efficacy in inorganic perovskite‐type photovoltaics.