Large guanidinium cation enhance photovoltage for perovskite solar cells via solution-processed secondary growth technique

•Large guanidinium cation was utilized to treat the surface of MAPbI3 films.•Perovskite solar cells have been prepared based on solution-processed secondary growth technique.•The presence of Gua molecules at the interfaceincreases all photovoltaic properties, in particular Voc.•The more n-type (Gua1−xMAx)PbI3 perovskite film was obtained to enhance the performance of the device. Recently, perovskite solar cells (PSCs) have been rapidly developed, counting as the most promising alternative to the Si solar cells, but non-radiative charge carrier recombination at grain boundaries limited open circuit voltages and consequent performance improvements of perovskite solar cells. In this work, a new perovskite film growth method was presented here using the organic molecule guanidinium (CH6N3+, Gua) to assist the secondary growth after the formation of perovskite films. It is found that the presence of Gua molecules at the interface between the perovskite film and the hole conductor layer increases all photovoltaic properties, in particular Voc as well as the operational stability of the PSCs. The optimum performance of the planar perovskite solar cells demonstrated a PCE of 18.54% with a higher Voc of 1.10 V and potent stability for 30 days in dark under dry condition. These results presented a simple method for suppressing non-radiative charge carrier loss in hybrid perovskite solar cells to further enhance the device performance toward highly efficient solar cells.