Cyclopentadithiophene cored A-π-D-π-A non-fullerene electron acceptor in ternary polymer solar cells to extend the light absorption up to 900 nm

Yuanxun Zhang, Xiaochen Liu, Huimin Gu, Lingpeng Yan, Hongwei Tan, Chang Qi Ma*, Yi Lin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

Conjugated small molecular non-fullerene electron acceptors (NFA) are considered as one of the critical materials for achieving high performance and low cost of polymer solar cells, and received much attention in the last few years. However, most of the NFAs are based on large fused π-aromatic core, which requires complicate synthesis efforts. In addition, the relatively weak light absorption limited to 800 nm of most the NAFs limits the energy harvesting capability of the solar cells. In this paper, we report an A-π-D-π-A type molecule cored with a cyclopentadithiophene unit, which can be easily synthesized in two steps from commercially available starting materials. This compound shows a broad absorption up to 900 nm in thin solid film, which is ascribed to the relatively high highest occupied molecular orbital (HOMO) energy level as confirmed by cyclic voltammery and theoratical calculation. Application of the compound in polymer solar cells was also investigated both in binary and in ternary systems. The optimized power conversion efficiency (PCE) in binary solar cell with PTB7-Th as donor is 5.76% with an open circuit voltage (VOC) of 0.838 V, a short circuit current (JSC) of 14.81 mA/cm2 and a fill factor (FF) of 46.4%. In the ternary solar cells which includes a second acceptor, PC71BM, the highest PCE achieved is 9.39% with a VOC of 0.803 V, a JSC of 19.01 mA/cm2, a FF of 61.6%, which is over 20% enhancement compared to the PTB7-Th:PC71BM system (PCE of 7.58%). This work develops a simple small molecule non-fullerene acceptor which can largely enhance the photo response in near infrared region to improve the performance of fullerene based organic solar cell.

Original languageEnglish
Article number105530
JournalOrganic Electronics
Volume77
DOIs
Publication statusPublished - Feb 2020

Keywords

  • Near IR absorption
  • Non-fullerene acceptor
  • Polymer solar cells
  • Ternary system

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