Reducing Trap-Assisted Recombination in Small Organic Molecule-Based Photovoltaics by the Addition of a Conjugated Block Copolymer

Kyuwan Cho, Jinseck Kim, So Yeon Yoon, Ka Yeon Ryu, Song Rim Jang, Bogyu Lim, Kyungkon Kim

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The performance of organic photovoltaics (OPVs) based on the small-molecule organic semiconductor p-DTS(FBTTh2)2 is greatly improved by the addition of a conjugated block copolymer composed of difluoroquinoxaline and thienopyrrolodione blocks (D130). The power conversion efficiency (PCE) of the p-DTS(FBTTh2)2-based OPV is improved from 5.08% to 6.75% by the addition of 5 wt% D130 to the photoactive layer, which is composed of p-DTS(FBTTh2)2 and a fullerene derivative. Current–voltage and grazing incidence wide-angle X-ray scattering analyses revealed that the addition of D130 significantly reduces the trap density of the device and changes the packing orientation of p-DTS(FBTTh2)2 from mostly edge-on to partially face-on. These changes greatly improve the charge carrier mobility of the OPV, indicating that D130 is highly compatible with p-DTS(FBTTh2)2. Furthermore, the addition of D130 improve the photostability of the OPV by reducing the burn-in loss under a light soaking intensity of 1 sun. The D130-based OPV maintained 34% of its initial PCE after a light soaking test for 858 h. In contrast, the PCE of the OPV without D130 reduced to 14% of its initial efficiency in the same time period.

Original languageEnglish
Article number1700630
JournalMacromolecular Rapid Communications
Issue number5
StatePublished - Mar 2018

Bibliographical note

Funding Information:
This research was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) under program number 20123010010140, and supported by the NRF under program numbers NRF-2015M1A2A2057506 and NRF-2016M1A2A2940914.

Publisher Copyright:
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • organic solar cell stability
  • organic solar cells
  • small molecule organic solar cells
  • ternary organic solar cells


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