Effcient and stable TiO_2 nanorod array structured perovskite solar cells in air: Co-passivation and synergistic mechanism

摘要

In recent years, single crystal TiO_2 nanorod arrays (TNRAs) with fewer grain boundaries for photo-generated electron transport and ordered channel structures for perovskite flling have been employed as electron transport layers for effcient perovskite solar cells (PSCs). However, further improvements in TNRA-based PSC performance are urgently needed because defects in the perovskite layer seriously hinder device effciency and stability. In this study, with TNRAs as the electron transport layer, CH_3NH_3PbI_3 (MAPbI_3) perovskite flms were prepared in air by a two-step spin coating method. The grain boundary defects and surface defects of the MAPbI_3 layer are co-passivated by octyl ammonium iodide (CH_3(CH_2)_7NH_3I, OAI) and choline chloride (HOCH_2CH_2N (CH_3)_3Cl, Ch), respectively, and the effects of the two passive materials on the power conversion effciency (PCE) and stability of TNRA-based PSCs are systematically investigated. The results reveal that the introduction of OAI facilitates the formation of intermolecular valence bonds between crystalline MAPbI_3 to enhance its structural stability, while Ch passivates the Pb-I antisite substitution defect and I vacancy defect on the perovskite flm surface. Compared with the pristine device, the optimal PCE of the passivated device increases from 18.86% to 20.08%, and the thermal, humid and long-term stability of the device is also improved.