A Universal Strategy of Perovskite Ink ‐ Substrate Interaction to Overcome the Poor Wettability of a Self‐Assembled Monolayer for Reproducible Perovskite Solar Cells

Abstract

Perovskite solar cells employing [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) self‐assembled monolayer as the hole transport layer have been reported to demonstrate a high device efficiency. However, the poor perovskite wetting on Me‐4PACz caused by poor perovskite ink interaction with the underlying Me‐4PACz presents significant challenges for fabricating efficient perovskite devices. A triple co‐solvent system comprising dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N‐methyl‐2‐pyrrolidone (NMP) is employed to improve the perovskite ink ‐ Me‐4PACz coated substrate interaction and obtain a uniform perovskite layer. In comparison to DMF‐ and DMSO‐based inks, the inclusion of NMP shows considerably higher binding energies of the perovskite ink with Me‐4PACz as revealed by density‐functional theory calculations. With the optimized triple co‐solvent ratio, the perovskite devices deliver high power conversion efficiencies of >20%, 19.5%, and ≈18.5% for active areas of 0.16, 0.72, and 1.08 cm2, respectively. Importantly, this perovskite ink–substrate interaction approach is universal and helps in obtaining a uniform layer and high photovoltaic device performance for other perovskite compositions such as MAPbI3, FA1−xMAxPbI3–yBry, and MA‐free FA1−xCsxPbI3–yBry.

Mixed Self‐Assembled Hole‐Transport Monolayer Enables Simultaneous Improvement of Efficiency and Stability of Perovskite Solar Cells

“…This decrease in efficiency is attributed to the decrease in short‐circuit current density ( J SC ) and fill factor (FF) with increasing ratio of Me‐4PACz, which can be inferred to the inability of Me‐4PACz to form a fully adherent and dense HTL/perovskite interface due to its high hydrophobic properties, despite having better HTL properties. [ 15 ] Consequently, the PSC in the 3:1 condition was optimized with improved photovoltaic properties, and in subsequent comparisons, mixed SAM refers to the mixed self‐assembled hole‐transport monolayer with MeO‐2PACz and Me‐4PACz in a ratio of 3:1.…”

Self‐assembled monolayers for perovskite solar cells

“…Reproduced with permission from refs. 112, 113, 20, 110, 8, 107, respectively. Copyright 2023 Wiley, Springer Nature, Wiley, Cell Press, AAAS, Wiley, respectively.…”

Mechanism of Solvent Engineering for Controlling the Room-Temperature Crystallization Kinetics of MAPbI3 Perovskite Polycrystals

“…In addition to their high photovoltaic performance, perovskite solar cells also have the advantages of solution processability, simple preparation process, and high cost-effectiveness, demonstrating enormous potential as the next generation of commercial solar cells. − The solution spin-coating method is widely used in the laboratory to prepare perovskites, combined with post-thermal annealing treatment (≥100 °C) to quickly remove solvents and achieve phase transformation. However, the restricted scalability and elevated energy consumption associated with the laboratory-scale preparation process hinder the widespread commercialization of perovskite materials. − For example, the annealing step that lasts for tens of minutes slows down the preparation process, complicating the fabrication of large-area thin films. − Besides, intense film formation during annealing usually induces uneven nucleation, and the thermal treatment may cause the loss of organic cations in perovskites, resulting in additional surface and interface defects. − …”