Electronic structure of the CsPbBr3/polytriarylamine (PTAA) system

James Endres, Michael Kulbak, Lianfeng Zhao, Barry P. Rand, David Cahen, Gary Hodes, Antoine Kahn

Research output: Contribution to journalArticle

50 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article number035304
JournalJournal of Applied Physics
Volume121
Issue number3
DOIs
StatePublished - Jan 21 2017

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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