Grain boundary passivation with triazine-graphdiyne to improve perovskite solar cell performance

Detrimental defects on perovskite grain boundaries (GBs) are critical factors that lead to non-radiative recombination and hysteresis. In this work, triazine-graph-diyne (Tra-GD), a nitrogen-rich two-dimensional (2D) material, was incorporated into the active layer of perovskite to modify the GBs. Tra-GD was found to distribute evenly over the bulk of the perovskite and has a strong interaction with the Pb2+ exposed at GBs, which enables it to effectively passivate GB defects and prevent ion migration. The results of Kelvin probe force microscopy and photoluminescence studies proved that the highly conjugated Tra-GD located at GBs could promote charge extraction and transport. Benefiting from defect passivation and more efficient carrier transport, the Tra-GD based device showed less non-radiative recombination loss. Consequently, the resultant device presented negligible hysteresis and yielded a high power conversion efficiency (PCE) of 20.33% in the MAPbI(3)-based perovskite solar cell. This approach was extended to the FAPbI(3) system with a PCE of 21.16%. Our Tra-GD passivation strategy provides a useful approach to effectively improving the device performance and addressing hysteresis issues.