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.

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.

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Methoxy-free donors are an emerging class of alternative methoxy triphenylamine materials toward stable organic hole-transporting materials (HTMs). However, low cost, stable and efficient methoxy-free donors are scarce. Moreover, the lack...

With perovskite-based solar cells (PSCs) now reaching efficiencies of greater than 20 %, the stability of PSC devices has become ac ritical challenge for commercialization. However,m ost efficient hole-transporting materials (HTMs) thus far still rely on the state-of-the-art methoxy triphenylamine (MOTPA) donor unit in whichm ethoxy groups usually reduce the device stability.H erein, ac arbazole-fluorene hybrid has been employed as am ethoxy-free donor to construct organic HTMs.The indeno[1,2-b]carbazole group not only inherits the characteristics of carbazole and fluorene,b ut also exhibits additional advantages arising from the bulky planar structure.Consequently,M129, endowed with indeno[1,2-b]carbazole simultaneously exhibits ap romising efficiency of over 20 %a nd superior long-term stability.T he hybrid strategy toward the methoxy-free donor opens an ew avenue for developing efficient and stable HTMs. Figure 1. Schematic illustration of the molecular design of M127-M129.