The spiro-type hole transport materials (HTMs) highly depend on the dopants, which increase the hygroscopicity and damage the stability of perovskite solar cells (PSCs). Herein we propose an effective linearization strategy and conjugate engineering modulation to improve the hole mobility and hydrophobicity of spiro-type HTMs. It is found that the spiro-type HTMs with a larger conjugation unit outperforms the short ones with respect to the power conversion efficiency (PCE) and long-term stability, regardless of whether or not the dopants are used. Due to good hole transport and film formation properties, the doped M6-F exhibits high efficiency in both large-area (1.01 cm2, 20.31%) and small-area (0.1 cm2, 22.17%) devices. Moreover, a PSC based on dopant-free M6-F yields an efficiency of 21.21% (stabilized PCE is 20.59%). This work provides a rational and effective way to break the bottleneck of developing spiro-type HTMs.

The extraordinary electronic and structural properties of carbazole make it an important donor for the molecular design of hole transport materials (HTMs). However, the development of peripheral carbazole donors has lagged behind. Herein, a series of low‐cost arylamine‐substituted carbazole donors are synthesized by a one‐step facile method. The effect of the terminal arylamine on the optoelectronic, thermal stability, hole mobility, and photovoltaic properties of the studied carbazole HTMs is also investigated. The diphenylamine‐ and carbazole‐substituted carbazoles possess the orthogonal–planar conformation, endowing the HTMs (M142 and M143) with excellent electronic properties and morphological properties. Consequently, power conversion efficiencies (PCEs) of 19.60% and 20.05% accompanied with a high photovoltage are achieved for M142‐ and M143‐based doped devices, respectively, outperforming the controlled cells based on nonsubstituted carbazole HTM (M145, PCE = 17.25%). Moreover, the devices based on M143 exhibit good long‐term storage, thermal, and light stability. This work provides a simple strategy for molecular design in developing efficient carbazole donors.

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