Lignin carbon dots as effective dopants and passivators for SnO₂ electron transport layers to achieve high-performance perovskite solar cells

Abstract

The low-temperature processing advantage of SnO₂ makes it a promising electron transport layer material for perovskite solar cells (PSCs). However, this advantage comes at the cost of the formation of oxygen-vacancy surface defects that hamper device performance. Here, by using bioresource lignin as precursors, we fabricate an effective dopant and passivator of lignin carbon dots to mitigate the defects of SnO2 and improve the PSC properties. Featuring the excellent compatibility and abundant surface groups of L-CDs, the defects of SnO2 are passivated and the trap-state density is reduced, the charge extraction/transfer is improved, the carrier accumulation and recombination are suppressed. These collective improvements result in significant performance improvements, including an 11.8 % reduction in trap-state density, a 251.7 % increase in electron mobility, and a 15.2 % enhancement in power conversion efficiency. Additionally, the device demonstrates improved long-term stability. This work addresses the limitations of SnO₂ and may expand its application in high-performance PSC fabrication.