A Universal Method of Perovskite Surface Passivation for CsPbX<sub>3</sub> Solar Cells with <i>V</i><sub>OC</sub> over 90% of the S‐Q limit
Zhanglin Guo, Shuai Zhao, Naoyuki Shibayama, Ajay Kumar Jena, Izuru Takei, Tsutomu Miyasaka
Abstract
Abstract In comparison to hybrid perovskite solar cells (PSCs), all‐inorganic CsPbX 3 PSCs suffer from larger V OC deficits, leading to inferior efficiency. The perovskite surface defects like iodine vacancy (V I ) are the main sources of nonradiative recombination causing a V OC deficit. Here, 2,5‐thiophenedicarboxylic acid (TDCA) is used to passivate the surface V I through the strong coordination interaction between the thiophene unit of TDCA and the undercoordinated Pb 2+ of perovskite. TDCA passivation also elevates the perovskite surface valence band position, leading to a better interfacial energy alignment. Consequently, the V OC of CsPbI 2.25 Br 0.75 PSCs is remarkably improved from 1.36 to 1.43 V (efficiency from 15.55% to 16.72%), reaching 92% (record‐high among CsPbX 3 PSCs) of the Shockley–Queisser V OC limit. This method also promotes the V OC of CsPbI 1.5 Br 1.5 cell from 1.42 to 1.51 V (90% of the limit) and CsPbIBr 2 cell from 1.44 to 1.54 V (87% of the limit), demonstrating its universality for CsPbX 3 perovskites.