Modulating the Self-Assembly of Coplanar D-π-D Hole-Transporting Materials via Alkyl Chain Engineering for Efficient and Stable Inverted Perovskite Solar Cells

作者：Luo, Ruixi; Zhao, Xin; Cai, Ning^*; Zhao, Jiehao; Wang, Tiejun; Min, Yonggang; Jen, Alex K. -Y.

来源：Solar RRL, 2023, 7(9).

DOI：10.1002/solr.202300070

• alkyl chain modulations
• hole-transporting materials
• inverted perovskite solar cells
• organic semiconductors
• self-assembly

Rational introduction of flexible alkyl chains into rigid conjugated molecules is a facile but effective strategy to develop advanced organic semiconductor materials for considerable enhancement of photovoltaic performance. Herein, seven hole-transporting materials (HTMs) via attaching ethyl, hexyl, or ethylhexyl to benzodithiophene pi-linker and bromoethyl, bromobutyl, or bromohexyl to phenoxazine donor (D), respectively, named B2P2, B6P2, B8P2, B6P4, B2P6, B6P6 (N01), and B8P6, are reported. Joint differential scanning calorimetry measurements and thin-film absorption spectra of representative HTMs, B8P6, B6P4, and B2P2 reveal that alkyl chain modulation on coplanar D-pi-D HTMs enables synchronous optimization of their solution processability, molecular packing, and thermal phase transition. Consequently, benefiting from the favorable self-assembly and surface characteristics of hole-transporting layers and further induced superior upper perovskite-growth, B8P6- and B6P4 -based inverted perovskite solar cells exhibit decent power conversion efficiencies of 20.67% and 20.13%, respectively, prior to that of amorphous B2P2 (19.04%). Analysis on steady-state/transient photoluminescence spectra and light intensity-dependent short-circuit photocurrent and open-circuit voltage (V-oc) demonstrates that more ordered assemblies of HTMs obtained via alkyl chain engineering can facilitate efficient interfacial charge transport/extraction and inhibit detrimental charge recombination, accounting for an enhanced V-oc and fill factor.

• 单位
  广东工业大学