Preparation of low-cost perovskite solar cells with high-quality perovskite films in an ambient atmosphere

Abstract

High-quality perovskite films are extremely crucial to obtain perovskite solar cells with excellent photovoltaic performance, especially for carbon-based hole transport materials (HTM)-free perovskite solar cells. In this work, a facile and low-cost double two-step method (DT-method) is developed to prepare uniform and pinhole-free CH3NH3PbI3 perovskite films in an ambient atmosphere by utilizing the dissolution-recrystallization of PbI2 in DMF. That is to spin-coat PbI2 and CH3NH3I solution sequentially onto pristine perovskite films prepared by the conventional two-step method. The solar cells fabricated by the DT-method show a dramatic performance improvement, including V oc, J sc, and fill factor reach 0.85 V, 15.56 mA cm−2, and 0.58 respectively, which increase power conversion efficiency from 3.93% to 7.58% compared with the conventional two-step method. The improvement in performance and stability of solar cells is mainly due to the higher coverage of perovskite films onto the underlying mesoporous TiO2 layer and a negligible amount of PbI2 residue, which can effectively reduce charge recombination and promote the rapid transfer of charge carriers. In summary, this work presents a process for preparing carbon-based HTM-free perovskite solar cells (PSCs) in a high-humidity atmospheric environment (60%–85%). This simple device structure and preparation condition can greatly reduce the production threshold and cost of PSCs.