Tail state limited photocurrent collection of thick photoactive layers in organic solar cells

Jiaying Wu, Joel Luke, Harrison Ka Hin Lee, Pabitra Shakya Tuladhar, Hyojung Cha, Soo Young Jang, Wing Chung Tsoi, Martin Heeney, Hongkyu Kang, Kwanghee Lee, Thomas Kirchartz, Ji Seon Kim, James R. Durrant

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

We analyse organic solar cells with four different photoactive blends exhibiting differing dependencies of short-circuit current upon photoactive layer thickness. These blends and devices are analysed by transient optoelectronic techniques of carrier kinetics and densities, air photoemission spectroscopy of material energetics, Kelvin probe measurements of work function, Mott-Schottky analyses of apparent doping density and by device modelling. We conclude that, for the device series studied, the photocurrent loss with thick active layers is primarily associated with the accumulation of photo-generated charge carriers in intra-bandgap tail states. This charge accumulation screens the device internal electrical field, preventing efficient charge collection. Purification of one studied donor polymer is observed to reduce tail state distribution and density and increase the maximal photoactive thickness for efficient operation. Our work suggests that selecting organic photoactive layers with a narrow distribution of tail states is a key requirement for the fabrication of efficient, high photocurrent, thick organic solar cells.
Original languageEnglish (US)
JournalNature Communications
Volume10
Issue number1
DOIs
StatePublished - Dec 1 2019
Externally publishedYes

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Chemistry
  • General Physics and Astronomy

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