High-performance perovskite solar cells using the graphene quantum dot–modified SnO₂/ZnO photoelectrode

Regardless of the excellent improvement in the assembling of perovskite solar cells (PSCs), the photon-harvesting performance of these devices is inadequate through the disproportionate recombination of generated charge carriers. The improvement of the charge carrier mobility can significantly reduce the recombination and help the perovskite devices reach the theoretical power conversion efficiency (PCE). The modification of charge selective contacts is one of the most effective approaches for reducing the carrier recombination. Herein, we introduce a facile and effective doping engineering approach based on graphene quantum dots (GQDs) for the modification of the SnO₂/ZnO bilayer electron transport layer (ETL). A comparative study of perovskite films deposited on SnO₂/ZnO layers with altered concentrations of GQDs was employed to significantly enhance the opto-electronic properties. The integration of GQDs into the ETL indicates a potential for improving the charge carrier transporting in PSCs. Overall, the PSC using the 4% GQD-modified ETL yields a PCE of 19.81% with a striking open-circuit voltage (V_OC) of 1.17 V. Besides, 4% GQD-modified ETL-based devices enhance the long-term ambient and thermal stability.