In this paper, two novel D‐π‐D hole‐transporting materials (HTM) are reported, abbreviated as BDT‐PTZ and BDT‐POZ, which consist of 4,8‐di(hexylthio)‐benzo[1,2‐b:4,5‐b′]dithiophene (BDT) as π‐conjugated linker, and N‐(6‐bromohexyl) phenothiazine (PTZ)/N‐(6‐bromohexyl) phenoxazine (POZ) as donor units. The above two HTMs are deployed in p‐i‐n perovskite solar cells (PSCs) as dopant‐free HT layers, exhibiting excellent power conversion efficiencies of 18.26% and 19.16%, respectively. Particularly, BDT‐POZ demonstrates a superior fill factor of 81.7%, which is consistent with its more efficient hole extraction and transport verified via steady‐state/transient fluorescence spectra and space‐charge‐limited current technique. Single‐crystal X‐ray diffraction characterization implies these two molecules present diverse packing tendencies, which may account for various interfacial hole‐transport ability in PSCs.

Delicately designed dopant‐free hole‐transporting materials (HTMs) with ordered structure have become one of the major strategies to achieve high‐performance perovskite solar cells (PSCs). In this work, we report two donor‐π linker‐donor (D‐π‐D) HTMs, N01 and N02, which consist of facilely synthesized 4,8‐di(n‐hexyloxy)‐benzo[1,2‐b:4,5‐b′]dithiophene as a π linker, with 10‐bromohexyl‐10H‐phenoxazine and 10‐hexyl‐10H‐phenoxazine as donors, respectively. The N01 molecules form a two‐dimensional conjugated network governed by C−H⋅⋅⋅O and C−H⋅⋅⋅Br interaction between phenoxazine donors, and synchronously construct a three‐dimension lamellar structure with the aid of interlaminar π–π interaction. Consequently, N01 as a dopant‐free small‐molecule HTM exhibits a higher intrinsic hole mobility and more favorable interfacial properties for hole transport, hole extraction and perovskite growth, enabling an inverted PSC to achieve a very impressive power conversion efficiency of 21.85 %.

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Delicately designed dopant-free hole-transporting materials (HTMs) with ordered structure have become one of the major strategies to achieve high-performance perovskite solar cells (PSCs). In this work, we report two donor-p linkerdonor (D-p-D) HTMs, N01 and N02,which consist of facilely synthesized 4,8-di(n-hexyloxy)-benzo[1,2-b:4,5-b']dithiophene as a p linker,w ith 10-bromohexyl-10H-phenoxazine and 10-hexyl-10H-phenoxazine as donors,r espectively.T he N01 molecules form at wo-dimensional conjugated network governed by C À H•••O and C À H•••Br interaction between phenoxazine donors,a nd synchronously construct at hreedimension lamellar structure with the aid of interlaminar p-p interaction. Consequently, N01 as ad opant-free small-molecule HTM exhibits ah igher intrinsic hole mobility and more favorable interfacial properties for hole transport, hole extraction and perovskite growth, enabling an inverted PSC to achieve av ery impressive power conversion efficiency of 21.85 %.

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