Reducing the Voc Loss of Hole Transport Layer-Free Carbon-Based Perovskite Solar Cells via Dual Interfacial Passivation

• Li2CO3 modification of SnO2 electron transport layer enables dual interfacial passivation, reducing Voc loss in HTL-free carbon-based perovskite solar cells. • The dual passivation mechanism involves enhanced charge extraction and optimized energy alignment at the ETL/perovskite interface, plus PbI2-induced defect suppression at the perovskite top surface. • The optimized C-PSC achieves a high PCE of 19.1% under standard illumination and a record-high PCE of 33.2% under indoor LED light (2000 lx, 3000 K). • This work provides a practical, low-cost approach to fabricate highly efficient carbon-based perovskite solar cells for indoor photovoltaic applications.