Grain Boundary Defects Passivated with tert-Butyl Methacrylate for High-Efficiency Perovskite Solar Cells

A high-quality perovskite film is critical to realize high-efficiency and hysteresis-less perovskite solar cells (PSCs). However, a solution-processed perovskite layer presents many ionic vacancies on grain boundaries, which serve as nonradiative recombination centers that cause a loss of photocurrent. Herein, a trace amount of Lewis base tert-butyl acrylate (TBA) with both effective C═O and C═C functional groups is introduced to synergistically control the crystallization process and saturate surface dangling bonds. The C═O groups of TBA strongly bond to the uncoordinated Pb2+ to be a more stable TBA-PbI2 Lewis adduct, slowing down the perovskite crystallization to form a high-crystalline quality film and suppressing the formation of nonradiative recombination defects at perovskite boundaries. In addition, the π–σ and π–π conjugated bonds of C═C and −C═O in TBA show a strong delocalized electron-rich structure, promoting the photogenerated charge carrier diffusion in the perovskite layer. As a consequence, the open-circuit voltage of a TBA-PSC is significantly increased from 1.07 to 1.12 V and the fill factor is improved from 78.20 to 81.56%. Thus, the TBA-PSC achieves a high power conversion efficiency of 22.82% with negligible hysteresis. Therefore, the TBA additive is a feasible and efficient method to improve the perovskite crystalline quality for high-performance PSCs.