Charge creation and recombination in multi-length scale polymer: fullerene BHJ solar cell morphologies

Subhrangsu Mukherjee, Xuechen Jiao, Harald Ade

Research output: Contribution to journalArticleResearchpeer-review

60 Citations (Scopus)


While the extremes in organic photovoltaic bulk heterojunction morphology (finely mixed or large pure domains) are easily understood and known to be unfavorable, efficient devices often exhibit a complex multi-length scale, multi-phase morphology. The impact of such multiple length scales and their respective purities and volume fractions on device performance remains unclear. Here, the average spatial composition variations, i.e., volume-average purities, are quantified at multiple size scales to elucidate their effect on charge creation and recombination in a complex, multi-length scale polymer:fullerene system (PBDTTPD:PC71BM). The apparent domain size as observed in TEM is not a causative parameter. Instead, a linear relationship is found between average purity at length scales <50 nm and device fill-factor. Our findings show that a high volume fraction of pure phases at the smallest length scales is required in multi-length scale systems to aid charge creation and diminish recombination in polymer:fullerene solar cells.

Original languageEnglish
Article number1600699
Number of pages8
JournalAdvanced Energy Materials
Issue number18
Publication statusPublished - 21 Sep 2016
Externally publishedYes


  • average domain purity
  • bulk-heterojunction
  • polymers
  • recombination
  • solar cells

Cite this