Surface Polarity Regulation by Relieving Fermi‐Level Pinning with Naphthalocyanine Tetraimides toward Efficient Perovskite Solar Cells with Improved Photostability
Qin Zhou, C.S. Cai, Qin Xiong, Zilong Zhang, Jianbin Xu, Lusheng Liang, Shibo Wang, Weihai Sun, Zhongyi Yuan, Peng Gao
Abstract
Abstract In perovskite solar cells (PSCs), defective perovskite grain boundaries (GBs) and/or surface due to photo‐excitation and the resulted suboptimal carrier dynamics at the perovskite/charge transport layer, have largely limited further performance enhancement and aggravated the PSCs instability. Fundamentally preventing the formation of these trap‐states through a simple and efficient approach is thus critical to the enhancement of both device performance and stability. Herein, a novel semiconductive silicon naphthalocyanine derivative (Cl‐SiNcTI) to reduce the deep level trap states at the GBs and the surface of perovskite film is successfully employed via a newly proposed photon‐relaxation mechanism. The resulting benign p‐type surface polarity and suppressed non‐radiation recombination lead to improved charge transport in bulk perovskite and at the perovskite/spiro‐OMeTAD interface. With a synergistic contribution of the Cl‐SiNcTI and 2‐(2‐Fluorophenyl)ethylamine iodide (oFPEAI), a 24.30% efficiency is achieved in a single cell with excellent operational stability. Moreover, under steady‐state light illumination, 93% power output compared to its initial state can still be maintained after 250 h of continuous operation.