Effective protection of sequential solution-processed polymer/fullerene bilayer solar cell against charge recombination and degradation

Lin Xie, Soyeon Yoon, Yun Ju Cho, Kyungkon Kim

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Abstract Both charge recombination and degradation in sequential solution processed polymer/fullerene bilayer organic photovoltaics (OPV) are effectively reduced by the insertion of a TiO2 inter-layer between the bilayer and Al electrode. The polymer/fullerene bilayer composed of a poly(3-hexylthiophene) (P3HT) bottom-layer and a [6,6] phenyl C61-butyric acid methyl ester (PCBM) top-layer shows significant change in morphology due to the substantial inter-penetration of P3HT and PCBM during the thermal annealing process. Consequently, the bilayer surface becomes P3HT rich resulting in significant charge recombination at the bilayer/Al interface of the bilayer OPV. The charge recombination rate of the bilayer OPV is reduced by one order of magnitude upon the insertion of a TiO2 nanoparticle inter-layer between the bilayer and the Al electrode after the thermal annealing process. In contrast, when the thermal annealing process is conducted after insertion of the inter-layer, the effect of the TiO2 inter-layer becomes insignificant. The VOC and efficiency of the bilayer OPV is greatly enhanced from 0.37 to 0.66 V and 1.2% to 3.7%, respectively by utilizing the properly constructed TiO2 inter-layer in the bilayer OPV. Additionally, insertion of the TiO2 inter-layer significantly improves the stability of the bilayer OPV. The bilayer OPV with a TiO2 inter-layer maintains 51% of its initial PCE after storage under dark ambient conditions for 700 h without encapsulation, whereas the bilayer OPV without a TiO2 inter-layer did not show any solar cell performance after 200 h under the same conditions.

Original languageEnglish
Article number3151
Pages (from-to)212-218
Number of pages7
JournalOrganic Electronics
Volume25
DOIs
StatePublished - 3 Jul 2015

Keywords

  • Bilayer solar cell
  • Charge recombination
  • Organic solar cell
  • TiO interlayer

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