Optimization of perovskite/carbon interface performance using N-doped coal-based graphene quantum dots and its mechanism analysis

Optimizing the interfacial properties between perovskite and carbon electrodes has always been an important way to improve the photoelectric conversion efficiency (PCE) of carbon-based perovskite solar cells (C-PSCs) and facilitate their commercialization. In this paper, nitrogen-doped graphene quantum dots (N-GQDs) with fluorescent properties were successfully prepared using inexpensive coal as raw material by a facile and environmentally friendly chemical reagent oxidation. The results show that the electron-rich pyridinic nitrogen in N-GQDs can act as Lewis bases to form coordination bonds with uncoordinated lead ions by sharing electron pairs, thereby reducing the defect density and nonradiative recombination of photo-generated electron-hole, and extending lifetime of charge carriers. In addition, due to the passivation of N-GQDs, the hysteresis effect of the device is significantly reduced and the long-term stability is also improved. By optimizing the concentration, the PCE of C-PSCs achieved a maximum of 14.31%, which was improved by 20.25% compared with 11.90% of the pristine C-PSCs. This work provides a facile, environmentally friendly and efficient strategy for improving the overall performance of C-PSCs using inexpensive coal-based N-GQDs.