Donor Derivative Incorporation: An Effective Strategy toward High Performance All-Small-Molecule Ternary Organic Solar Cells

Hua Tang; Tongle Xu; Cenqi Yan; Jie Gao; Hang Yin; Jie Lv; Ranbir Singh; Manish Kumar; Tainan Duan; Zhipeng Kan; Shirong Lu; Gang Li

doi:10.1002/advs.201901613

Donor Derivative Incorporation: An Effective Strategy toward High Performance All-Small-Molecule Ternary Organic Solar Cells

Adv Sci (Weinh). 2019 Sep 4;6(21):1901613. doi: 10.1002/advs.201901613. eCollection 2019 Nov 6.

Authors

Hua Tang^{1

2

3}, Tongle Xu^{1

2}, Cenqi Yan³, Jie Gao¹, Hang Yin³, Jie Lv^{1

2}, Ranbir Singh⁴, Manish Kumar⁵, Tainan Duan¹, Zhipeng Kan¹, Shirong Lu¹, Gang Li³

Affiliations

¹ Chongqing Institute of Green and Intelligent Technology Chinese Academy of Sciences Chongqing 400714 China.
² University of Chinese Academy of Sciences Beijing 100049 China.
³ Department of Electronic and Information Engineering The Hong Kong Polytechnic University Hong Hum Kowloon Hong Kong China.
⁴ Department of Energy & Materials Engineering Dongguk University Seoul 04620 Republic of Korea.
⁵ Pohang Accelerator Laboratory Pohang University of Science and Technology Pohang 37673 Republic of Korea.

Abstract

Thick-film all-small-molecule (ASM) organic solar cells (OSCs) are preferred for large-scale fabrication with printing techniques due to the distinct advantages of monodispersion, easy purification, and negligible batch-to-batch variation. However, ASM OSCs are typically constrained by the morphology aspect to achieve high efficiency and maintain thick film simultaneously. Specifically, synchronously manipulating crystallinity, domain size, and phase segregation to a suitable level are extremely challenging. Herein, a derivative of benzodithiophene terthiophene rhodanine (BTR) (a successful small molecule donor for thick-film OSCs), namely, BTR-OH, is synthesized with similar chemical structure and absorption but less crystallinity relative to BTR, and is employed as a third component to construct BTR:BTR-OH:PC₇₁BM ternary devices. The power conversion efficiency (PCE) of 10.14% and fill factor (FF) of 74.2% are successfully obtained in ≈300 nm OSC, which outperforms BTR:PC₇₁BM (9.05% and 69.6%) and BTR-OH:PC₇₁BM (8.00% and 65.3%) counterparts, and stands among the top values for thick-film ASM OSCs. The performance enhancement results from the enhanced absorption, suppressed bimolecular/trap-assisted recombination, improved charge extraction, optimized domain size, and suitable crystallinity. These findings demonstrate that the donor derivative featuring similar chemical structure but different crystallinity provides a promising third component guideline for high-performance ternary ASM OSCs.

Keywords: morphology; organic solar cells; small molecules; structural similarity; thick films.