Dual-layer synergetic optimization of high-efficiency planar perovskite solar cells using nitrogen-rich nitrogen carbide as an additive

Abstract

Defects and energy-level offsets in distinct functional layers of perovskite solar cells (pero-SCs) are recognized obstacles to achieving their high efficiency and long-term stability. Herein, we report the meticulous design and positioning of nitrogen-rich nitrogen carbide (g-C₃N₅) as a multifunctional additive to simultaneously optimize the intrinsic defects of a SnO₂ electron transport layer (ETL) and perovskite layer for high-performance pero-SCs. The synergistic effect of the favorable band alignment and improved electrical conductivity, obtained by precisely positioning g-C₃N₅, enables the power conversion efficiency (PCE) of pero-SCs to be increased from 18.05% (g-C₃N₅-free) to 20.68% and significantly enhances the photo/thermal stability. Moreover, this multiple optimization strategy is also generalized to CsFAMA-based pero-SCs, achieving a champion PCE of 22.34%. Theoretical and experimental analyses further reveal that the incorporating of g-C₃N₅ regulates the crystalline quality, passivates grain boundary/surface defects and boosts the moisture resistance of photovoltaic devices. This work proves the charming properties and ingenious design of g-C₃N₅ as a multifunctional material for a variety of optoelectronic devices, including light-emitting diodes, photodetectors, sensors, etc.