Effects of blend composition on the morphology of Si-PCPDTBT:PC71BM bulk heterojunction organic solar cells

Rui Lin*, Matthew Wright, Binesh Puthen-Veettil, Xiaoming Wen, Murad J. Y. Tayebjee, Ashraf Uddin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

This work investigates the effects of the solution blend composition on the morphology of binary bulk heterojunction organic solar cells composed of poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta2,1-b:3,4-b′]dithiophene-siloe 2,6-diyl]] (Si-PCPDTBT) and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM). The polymer-fullerene ratio was varied from 2:9 to 1:1 (PC71BM weight ratio from 82 to 50 wt%). The dependence of the self-assembly of the polymer phase on the blend composition was investigated using X-ray diffraction measurements. A high polymer loading is required to allow the formation of large crystalline polymer domains in this materials system. X-ray photoelectron spectroscopy measurements revealed that this blend compositional dependence on the crystalline domain size correlated with a gradual alteration of the vertical phase distribution of polymer throughout the active layer. Using photoluminescence and short-circuit current results, we show that the efficacy of exciton dissociation is highly dependent on the solution blend composition. Coupled with mobility measurements, which indicate the hole mobility is also heavily dependent upon the content of polymer in the film, we explain the optimum blend performance of Si-PCPDTBT:PC71BM organic solar cells which occurs at a blend ratio of 2:3.

Original languageEnglish
Pages (from-to)1931-1940
Number of pages10
JournalPhysica Status Solidi (A) Applications and Materials Science
Volume212
Issue number9
DOIs
Publication statusPublished - Sep 2015
Externally publishedYes

Keywords

  • blend composition
  • fullerenes
  • morphology
  • organic solar cells
  • PC₇₁BM
  • polymers
  • Si-PCPDTBT

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