The Polymer Society of Korea

Abstract

Liquid 4-tert-butylpyridine (tBP) is widely used in n-i-p perovskite solar cells because it dissolves the Li-TFSI dopant and helps stabilize Li⁺. However, owing to its volatility and corrosive character, tBP can damage the perovskite absorber and, under heat, aggravate interfacial side reactions that generate byproducts and pinholes in the hole-transport layer, leading to device degradation. To address this issue, we employ 4-(N-carbazolyl)pyridine (4CP), a non-volatile solid additive that coordinates Li⁺ and suppresses the formation of Li_xO_y. Perovskite solar cells (PSCs) with 4CP deliver a 26.2% power conversion efficiency (PCE) and retain 80% of the initial output for >3000 h under maximum power point tracking. Unencapsulated PSCs also preserve 90% of the starting PCE after 200 thermal-shock cycles between -80 and 80 °C, and during continuous aging at 65 and 85 °C. These results identify 4CP as a practical approach to boost operational stability in n-i-p PSCs.