Electronic structure of the CsPbBr3/polytriarylamine (PTAA) system

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  • James Endres
    Princeton University 1 Department of Electrical Engineering, , Princeton, New Jersey 08544, USA
  • Michael Kulbak
    Weizmann Institute of Science 2 Department of Materials and Interfaces, , Rehovot, Israel
  • Lianfeng Zhao
    Princeton University 1 Department of Electrical Engineering, , Princeton, New Jersey 08544, USA
  • Barry P. Rand
    Princeton University 1 Department of Electrical Engineering, , Princeton, New Jersey 08544, USA
  • David Cahen
    Weizmann Institute of Science 2 Department of Materials and Interfaces, , Rehovot, Israel
  • Gary Hodes
    Weizmann Institute of Science 2 Department of Materials and Interfaces, , Rehovot, Israel
  • Antoine Kahn
    Princeton University 1 Department of Electrical Engineering, , Princeton, New Jersey 08544, USA

Description

<jats:p>The inorganic lead halide perovskite CsPbBr3 promises similar solar cell efficiency to its hybrid organic-inorganic counterpart CH3NH3PbBr3 but shows greater stability. Here, we exploit this stability for the study of band alignment between perovskites and carrier selective interlayers. Using ultraviolet, X-ray, and inverse photoemission spectroscopies, we measure the ionization energy and electron affinities of CsPbBr3 and the hole transport polymer polytriarylamine (PTAA). We find that undoped PTAA introduces a barrier to hole extraction of 0.2–0.5 eV, due to band bending in the PTAA and/or a dipole at the interface. p-doping the PTAA eliminates this barrier, raising PTAA's highest occupied molecular orbital to 0.2 eV above the CsPbBr3 valence band maximum and improving hole transport. However, IPES reveals the presence of states below the PTAA lowest unoccupied molecular level. If present at the CsPbBr3/PTAA interface, these states may limit the polymer's efficacy at blocking electrons in solar cells with wide band gap materials like CsPbBr3 and CH3NH3PbBr3.</jats:p>

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