Reinforcing CsPbI3 all-inorganic perovskite grain boundaries through bilateral cyano-based molecular cross-linking for efficient and stable solar cells

CsPbI3 all-inorganic perovskite solar cells (PSCs) are highly promising for photovoltaics owing to their excellent thermal stability and suitable bandgap. However, their performance and operational stability are often compromised by weak grain boundaries accompanied by a high density of defects. To overcome this limitation, we introduce succinonitrile (SN) as a multifunctional additive. SN features a flexible carbon chain terminated with cyano (–C≡N) groups at both ends, enabling it to coordinate strongly with Pb2+ via Lewis acid–base interactions and thereby act as a molecular cross-linker between adjacent grains. This bilateral coordination facilitates controlled crystallization, improves film morphology, passivates grain-boundary defects, and increases moisture resistance. As a result, the power conversion efficiency of SN-modified CsPbI3 PSCs increases from 14.52% to 16.17%, accompanied by significantly improved environmental stability. This work provides useful guidance for the design of efficient additives toward high-performance and stable all-inorganic CsPbI3 PSCs.