Hydroxylated coal-derived graphene oxide as a multifunctional interlayer enabling high-performance carbon-based perovskite solar cells

Graphene nanomaterials exhibit significant potential for carbon-based perovskite solar cells (C-PSCs); however, functionalized graphene derivatives remain relatively underexplored for interfacial engineering, particularly for cost-effective coal-derived materials. This study introduces a pioneering chemical modification approach using homemade coal-derived graphene oxide (GO) to synthesize two distinct functionalized graphene derivatives: hydroxylated graphene oxide (GO-OH) and carboxyl-functionalized graphene oxide (GO-COOH). Experimental results indicated that the excessive acidity of GO-COOH induces the degradation of perovskite film. Therefore, we constructed two device architectures: pritine (FTO/SnO 2 /MAPbI 3 /CE) and GO-OH-modified C-PSCs (FTO/SnO 2 /MAPbI 3 /GO-OH/CE) to investigate the impace of GO-OH incorporation on Photoelectric performance. The optimized device achieves a substantial 20.4 % boost in power conversion efficiency (PCE), increasing from 13.42 % to 16.16 %. Mechanistic investigations reveal that GO-OH serves a dual function: passivating deep-level defects (Pb 2+ and Pb 0 ) to optimize energy level alignment while simultaneously promoting perovskite grain growth, which enhances charge transport and boosts fill factor ( FF ) and short-circuit current density ( J sc ). Furthermore, the incorporation of the GO-OH interlayer facilitates efficient carrier extraction and maintains 90 % of its initial PCE after 30 days of ambient exposure, demonstrating remarkable stability. This work pioneers the application of functionalized coal-derived graphene oxide in C-PSCs, offering a novel and scalable strategy for enhancing both efficiency and stability.