Triphenylamine (TPA)-Functionalized Structural Isomeric Polythiophenes as Dopant Free Hole-Transporting Materials for Tin Perovskite Solar Cells

Rajendiran Balasaravanan, Chun Hsiao Kuan, Shih Min Hsu, En Chi Chang, Yu Cheng Chen, Yi Tai Tsai, Meng Li Jhou, Shueh Lin Yau, Cheng Liang Liu, Ming Chou Chen, Eric Wei Guang Diau

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7 Scopus citations

Abstract

A new series of triphenylamine (TPA)-functionalized isomeric polythiophenes are developed as hole transporting materials (HTM) for inverted tin-based perovskite solar cells (TPSCs). Bithiophene (BT) is first functionalized with two TPA (electron donor; D) at 3 and 5 positions to give two structural isomeric compounds (3BT2D and 5BT2D). The functionalized BT2Ds are then coupled with 3,3′-bis(tetradecylthio)-2,2′-bithiophene (SBT-14)/3,3′-ditetradecyl-2,2′-bithiophene (BT-14) to produce structural isomeric polythiophenes (1-4), which are compared to conventional poly[N,N″-bis(4-butylphenyl)-N,N″-bis(phenyl)-benzidine] (poly-TPD) as HTMs for TPSCs. With the appropriate alignment of energy levels with regard to the perovskite layer, the TPA-functionalized polymers-based TPSCs exhibit enhanced operational stability and efficiency. Moreover, the long thiotetradecyl chain in SBT-14 with intramolecular S(alkyl)∙∙∙S(thio) interactions restricts the molecular rotation and has a strong impact on the molecular solubility and wettability of the film during device fabrication. Among all the polymers studied, TPSCs fabricated with 3-SBT-BT2D polymer exhibit the highest hole mobility as well as the slowest charge recombination and achieve the highest power conversion efficiency of 8.6%, with great long-term stability for the performance retaining ≈90% of its initial values for shelf storage over 4000 h, which is the best efficiency for non-PEDOT:PSS-based TPSCs ever reported.

Original languageEnglish
Article number2302047
JournalAdvanced Energy Materials
Volume13
Issue number38
DOIs
StatePublished - 13 Oct 2023

Keywords

  • polymeric hole transporting materials
  • power conversion efficiency
  • thioalkylated bithiophenes
  • tin perovskite solar cells
  • triphenylamine

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