Tailored graphene quantum dots to passivate defects and accelerate charge extraction for all-inorganic CsPbIBr₂ perovskite solar cells

Graphene quantum dots (GQDs) have shown great potential to simultaneously improve the stability and efficiency of perovskite solar cells (PSCs). However, their preparation is either extremely harsh or inefficient, which severely hampers the extensive research and application. Herein, a novel solid-liquid interfacial exfoliation technique is established to fabricate high-quality GQDs from carbon fiber, in which the throughput of GQDs is up to 20 g in one pot with yield over 90%. To explore their role in PSC, nitrogen and sulfur functionalized GQDs have been further synthesized via a hydrothermal method, and used to regulate the interfacial properties of all-inorganic CsPbIBr₂ PSC. Arising from the interaction based on Lewis acid-base chemistry between GQDs and the under-coordinated Pb²⁺, the detrimental non-radiative recombination is significantly reduced, especially for the functionalized GQDs tailored PSC, leading to the champion efficiency of 9.80% for carbon-electrode based CsPbIBr₂ PSCs with excellent long-term stability.