"Solvent annealing" effect in polymer solar cells based on poly(3-hexylthiophene) and methanofullerenes

Gang Li, Yan Yao, Hoichang Yang, Vishal Shrotriya, Guanwen Yang, Yang Yang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

1081 Citations (Scopus)

Abstract

The self-organization of the polymer in solar cells based on regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied systematically as a function of the spin-coating time ts(varied from 20-80 s), which controls the solvent annealing time ta, the time taken by the solvent to dry after the spin-coating process. These blend films are characterized by photoluminescence spectroscopy, UV-vis absorption spectroscopy, atomic force microscopy, and grazing incidence X-ray diffraction (GIXRD) measurements. The results indicate that the π-conjugated structure of RR-P3HT in the films is optimally developed when tais greater than 1 min (ts-50 s). For ts< 50 s, both the short-circuit current (JSC) and the power conversion efficiency (PCE) of the corresponding polymer solar cells show a plateau region, whereas for 50 < ts< 55 s, the JSCand PCE values are significantly decreased, suggesting that there is a major change in the ordering of the polymer in this time window. The PCE decreases from 3.6% for a film with a highly ordered π-conjugated structure of RR-P3HT to 1.2 % for a less-ordered film. GIXRD results confirm the change in the ordering of the polymer. In particular, the incident photon-to-electron conversion efficiency spectrum of the less-ordered solar cell shows a clear loss in both the overall magnitude and the long-wavelength response. The solvent annealing effect is also studied for devices with different concentrations of PCBM (PCBM concentrations ranging from 25 to 67 wt %). Under "solvent annealing" conditions, the polymer is seen to be ordered even at 67 wt % PCBM loading. The open-circuit voltage (VOC) is also affected by the ordering of the polymer and the PCBM loading in the active layer. KGaA,.
Original languageEnglish
Pages (from-to)1636-1644
Number of pages9
JournalAdvanced Functional Materials
Volume17
Issue number10
DOIs
Publication statusPublished - 9 Jul 2007
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Condensed Matter Physics
  • Electrochemistry

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