A dual passivation strategy based on F/N co-doped coal-based graphene quantum dots for high-efficiency carbon-based perovskite solar cells

Abstract

The defects of perovskite films themselves and the energy-level mismatch with the carbon electrode (CE) limit the power conversion efficiency (PCE) and stability of carbon-based perovskite solar cells (C-PSCs). Therefore, the defect passivation of perovskite films and energy-level modification are crucial for the further improvement of the PCE and stability of C-PSCs. Here, for the first time, a dual passivation strategy based on F/N co-doped graphene quantum dots (F/N-GQDs) derived from coal was used to passivate deep-level defects such as Pb²⁺ and Pb⁰, optimize the energy-level alignment, and improve the hydrophobicity of perovskite films. The mechanism of the dual passivation strategy was systematically analyzed from the perspective of the structure and energy levels. As a result, the C-PSCs based on the dual passivation strategy obtained a PCE of 16.37%, which is 27.20% higher than that of the pristine device. Moreover, the optimized C-PSC maintains 92.5% of its initial PCE after aging for 30 days in an air atmosphere, and 68.6% of its initial PCE after heating at 60 °C for 15 days, indicating higher environmental and thermal stability. This work provides a facile, environmentally friendly and efficient strategy for improving the overall performance of C-PSCs using inexpensive coal-based F/N-GQDs.