Morphological Requirements for Nanoscale Electric Field Buildup in a Bulk Heterojunction Solar Cell

Kyra N. Schwarz, Valerie D. Mitchell, Saeed Uz Zaman Khan, Calvin Lee, Adam Reinhold, Trevor A. Smith, Kenneth P. Ghiggino, David J. Jones, Barry P. Rand, Gregory D. Scholes

Research output: Contribution to journalArticlepeer-review

Abstract

The morphology of organic semiconductors is critical to their function in optoelectronic devices and is particularly crucial in the donor-acceptor mixture that comprises the bulk heterojunction of organic solar cells. Here, energy landscapes can play integral roles in charge photogeneration, and recently have been shown to drive the accumulation of charge carriers away from the interface, resulting in the buildup of large nanoscale electric fields, much like a capacitor. In this work we combine morphological and spectroscopic data to outline the requirements for this interdomain charge accumulation, finding that this effect is driven by a three-phase morphology that creates an energetic cascade for charge carriers. By adjusting annealing conditions, we show that domain purity, but not size, is critical for an electro-absorption feature to grow-in. This demonstrates that the energy landscape around the interface shapes the movement of charges and that pure domains are required for charge carrier buildup that results in reduced recombination and large interdomain nanoscale electric fields.

Original languageEnglish (US)
Pages (from-to)537-545
Number of pages9
JournalJournal of Physical Chemistry Letters
Volume12
Issue number1
DOIs
StatePublished - Jan 14 2021

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Physical and Theoretical Chemistry

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