Non-Conjugated Polymer Based on Polyethylene Backbone as Dopant-Free Hole-Transporting Material for Efficient and Stable Inverted Quasi-2D Perovskite Solar Cells

Quasi-2D perovskites with excellent stability have been recognized as an alternative to 3D counterparts for perovskite solar cells (PSCs). Although the power conversion efficiency (PCE) of quasi-2D PSCs has increased over 18% by the compositional controlling and solvent engineering of perovskites, fewer studies have been conducted to exploit charge transport layers and investigate their interface relationships with quasi-2D perovskites. To achieve high efficiency and good long-term stability for quasi-2D PSCs, hole-transporting materials (HTMs) with matched energy levels and good chemical compatibility with quasi-2D perovskites are explored and investigated. Herein, a novel non-conjugated polymer based on polyethylene backbone, poly[3,6-(4,4′-dimethoxytriphenylamino)-9-vinyl-9H-carbazole] (PVCz-OMeTPA), is easily synthesized and investigated as a promising dopant-free HTM for quasi-2D PSCs. Due to its more suitable energy levels, good hole mobility, as well as excellent film-forming ability to assist the formation of high-quality quasi-2D perovskite films, the optimized p–i–n structured quasi-2D PSCs based on PVCz-OMeTPA exhibit the best PCE of 17.22%. The unencapsulated quasi-2D PSCs based on PVCz-OMeTPA maintain 82% of the initial efficiency after 1400 h under a relative humidity of ≈40% and sustain over 81% of the original efficiency after aging for 600 h upon 70 °C of continuous annealing.