Hydrophobic 2D Perovskite‐Modified Layer with Polyfunctional Groups for Enhanced Performance and High Moisture Stability of Perovskite Solar Cells

Abstract

The charges stuck in trap sites hinder charge transport and lead to Voc below the radiative limit, which seriously restrict the performance and stability of organic–inorganic halide perovskite solar cells (PSCs). Chemical passivation is an effective method to reduce defects and suppress nonradiative recombination. Herein, a new passivation molecule l‐cysteine methyl ester hydrochloride (CME) with thiol and ester groups is designed to modify the interface between the perovskite layer and hole transport layer (HTL). It reveals that thiol possesses outstanding moisture resistance and ester suppresses nonradiative recombination by coordinating with undercoordinated Pb2+. Furthermore, the 2D modified layer at the grain boundaries and surface passivates surface defects and promotes hole extraction. As a result, the CME device achieves the highest PCE of 20.33% with an enhanced open‐circuit voltage (Voc) of 1.11 V. Due to the barrier of highly hydrophobic 2D perovskites, the modified devices show excellent stability while exposed to humidity and high‐temperature environment. A facile and effective strategy to design organic molecular structures with polyfunctional groups to passivate trap‐assisted nonradiative recombination at the surface and grain boundaries is provided.

Above 23% Efficiency by Binary Surface Passivation of Perovskite Solar Cells Using Guanidinium and Octylammonium Spacer Cations

“…The long-chain alkylammonium cations have been reported to improve device performance via chemical passivation of the undercoordinated bonds on perovskite surface, creating a physical barrier against ion extraction from the perovskite absorber. [60,61] In addition, due to their hydrophobic nature, they can enhance ambient stability of the device. [62] On the other hand, guanidinium salts have been reported to improve cell performance via formation of compact and well-ordered crystal grains in the perovskite film, which can decrease recombination sites.…”

Hole-Transporting Vanadium-Containing Oxide (V2O5–x) Interlayers Enhance Stability of α-FAPbI3-Based Perovskite Solar Cells (∼23%)

“…It is necessary to introduce an interlayer that protects the perovskite absorbers from external stress, such as moisture, to retain photoactive α-FAPbI 3 and at the same time eliminate the detrimental reaction between Spi and metal electrodes. However, especially in n-i-p configuration PSCs, both materials and adoptable processes are entirely restricted due to the inherent susceptibility of the perovskites and organic substances, and for this reason, only methods such as device encapsulation, perovskite passivation with hydrophobic 2D cations, and modifying organic HTLs were mainly suggested. ,− The deposition temperature of interlayers should be low enough not to degrade the perovskites and/or organic substances of PSCs and the chemical environment capable of minimizing the photovoltaic performance of PSCs. In addition to such a challenging deposition condition, the interlayers should possess an electrically favorable configuration with underlying perovskite absorbers.…”

Combined Bulk and Surface Passivation in Dimensionally Engineered 2D‐3D Perovskite Films via Chlorine Diffusion

“…Most reports of bulk incorporated 2D perovskite have attributed passivation effects to the preferential formation of 2D perovskite phases at the 3D perovskite grain boundaries, and a consequent reduction in crystal defects in these regions. [ 5h,9 ] On the other hand, ultra‐thin 2D perovskite films or unreacted spacer cation compounds applied to the surface of 3D perovskite films can chemically‐passivate undercoordinated Pb atoms [ 10 ] or other interfacial defects at the perovskite‐transport layer interfaces, improving both V OC and PCE. [ 5a–g , i , l–n , p , 6b,8 ] Therefore, combining the bulk and surface passivation benefits of dimensional engineering into a single processing step is an attractive and cost‐effective strategy [ 11 ] to maximize mixed‐dimensional PSC performance.…”