Indeno[1,2‐b]carbazole as Methoxy‐Free Donor Group: Constructing Efficient and Stable Hole‐Transporting Materials for Perovskite Solar Cells

Abstract

With perovskite‐based solar cells (PSCs) now reaching efficiencies of greater than 20 %, the stability of PSC devices has become a critical challenge for commercialization. However, most efficient hole‐transporting materials (HTMs) thus far still rely on the state‐of‐the‐art methoxy triphenylamine (MOTPA) donor unit in which methoxy groups usually reduce the device stability. Herein, a carbazole‐fluorene hybrid has been employed as a methoxy‐free donor to construct organic HTMs. The indeno[1,2‐b]carbazole group not only inherits the characteristics of carbazole and fluorene, but also exhibits additional advantages arising from the bulky planar structure. Consequently, M129, endowed with indeno[1,2‐b]carbazole simultaneously exhibits a promising efficiency of over 20 % and superior long‐term stability. The hybrid strategy toward the methoxy‐free donor opens a new avenue for developing efficient and stable HTMs.

Development of Dopant‐Free Organic Hole Transporting Materials for Perovskite Solar Cells

“…Meanwhile, hysteresis free small scaled devices based on XY1 showed a competitive PCE of 18.78%. Further, several novel chemical structures of dopant‐free HTMs with moderate device data have been reported (summarized in Table 1 and 2) yet not discussed in detail here …”

A new strategy for constructing a dispiro-based dopant-free hole-transporting material: spatial configuration of spiro-bifluorene changes from a perpendicular to parallel arrangement

“…It means that WH-1 can effectively extract holes and retard trap induced nonradiative carrier recombination. 30 The parallel arrangement structure of two fluorene planes in WH-1 leads to better electronic contact between perovskite and WH-1, which promotes effective hole transfer and extraction. 26 Based on the above discussion, WH-1 as a dopant-free HTM has great application potential in PSCs.…”

A Review on Solution‐Processable Dopant‐Free Small Molecules as Hole‐Transporting Materials for Efficient Perovskite Solar Cells

“…In parallel with these donor-acceptor type SM-HTMs, those with only donor units were also attractive. [153][154][155][156][157][158] In 2017, the carbazole-based SM-HTM reached its first PCE of over 15%, where Li et al [153] anchored three carbazole units on the phenol core, and the molecule TCP-OH presented a well-aligned HOMO level with the VBM level of perovskite to transfer the holes and a large bandgap (E g ) to afford a quite shallow LUMO level to efficiently block the photogenerated electrons. The corresponding PSC device delivered a PCE of 16.97% and a better long-term stability relative to the spiro-OMeTAD device due to the higher T g .…”