All-inorganic CsPbBr3 perovskite solar cells with enhanced efficiency by exploiting lone pair electrons via passivation of crystal boundary using carbon nitride (g-C3N4) nanosheets

Fast extraction of photo-generated charge plays a crucial function in improving the photovoltaic conversion efficiency (PCE) of the perovskite solar cells (PSCs). Here, an effective strategy to decrease the charge recombination losses by introducing versatile carbon nitride ( g -C 3 N 4 ) nanosheets to the CsPbBr 3 films was demonstrated. The incorporation of the g -C 3 N 4 additive can restrain the nucleation and crystalline growth rate of perovskite films by an interaction of lone pair electrons from the exposed N atoms to the PbBr 2 precursor, resulting in high-quality CsPbBr 3 films with an increase in crystalline size. Notably, a ‘coupling effect’ between the lone pair electrons from g -C 3 N 4 nanosheets and unsaturated Pb dangling bonds (Br vacancies) around the grain boundaries significantly decreases trap states caused by defects, leading to the fewer recombination centers in CsPbBr 3 films. The g -C 3 N 4 nanosheets serving as an energy barrier can also successfully suppress the recombination loss of back electrons with holes from the g -C 3 N 4 interface, yielding a superior PCE of 8.0% with a fill factor of 80.25%. The result opens an alternative path to enhance the performance of CsPbBr 3 PSCs by passivating the trap states of perovskite films with the improvement of the crystallization quality and charge extraction efficiency.