Interfacial Engineering Using C-3 Alkyl Linker-Based Carbazole-Derived SAM Layers to Achieve 41.77% Indoor Efficiency in Wide-Bandgap Perovskite Solar Cells

Abstract

The unique molecular properties of carbazole-derived-phosphonic acid-base self-assembled monolayers (SAMs), have great potential in applying perovskite solar cells (PSCs) and optoelectronic devices. SAMs have been successfully used in PSCs and wide bandgap (WBG)-indoor PSCs with excellent hole-extraction and minimize energy loss at the interface defects. Surprisingly, nearly all SAMs reported with an even number of carbons chain linkers (i.e., 2, 4, and 6) are used to connect the carbazole and phosphonic acid fragment. In this work, three SAMs with a n-propyl chain (3C) linker with substitutes (R = H, methoxy, and phenyl) on the carbazole are investigated, designated as 3C-H, 3C-OMe, and 3C-Ph. These SAMs function as stand-alone hole-selective layers anchored on ITO/nickel oxide (NiO_x) in a p-i-n device architecture. WBG Cs_0.18FA_0.82Pb(I_0.8Br_0.2)₃ perovskite films are deposited onto ITO/NiO_x layers functionalized with the SAMs. PSCs based on 3C-Ph exhibited an open-circuit voltage (V_OC) of 1.23 V, a short-circuit current density (J_SC) of 21.53 mA cm⁻², and a maximum power conversion efficiency (PCE) of 21.59% under AM 1.5G illumination. Additionally, under indoor lighting conditions, 3C-Ph-based PSCs achieved a J_SC of 280.37 µA cm⁻², a V_OC of 1.09 V, and a fill factor of 81.43%, resulting in an overall maximum PCE of 41.77%.