High-Performance Organic Solar Cells Featuring Double Bulk Heterojunction Structures with Vertical-Gradient Selenium Heterocyclic Nonfullerene Acceptor Concentrations

Hao-Wen Cheng; Anisha Mohapatra; Yi-Ming Chang; Chuang-Yi Liao; Yu-Tang Hsiao; Chung-Hao Chen; Yu-Che Lin; Shih-Yu Huang; Bin Chang; Yang Yang; Chih-Wei Chu; Kung-Hwa Wei

doi:10.1021/acsami.1c06762

High-Performance Organic Solar Cells Featuring Double Bulk Heterojunction Structures with Vertical-Gradient Selenium Heterocyclic Nonfullerene Acceptor Concentrations

ACS Appl Mater Interfaces. 2021 Jun 16;13(23):27227-27236. doi: 10.1021/acsami.1c06762. Epub 2021 Jun 6.

Authors

Hao-Wen Cheng^{1

2}, Anisha Mohapatra³, Yi-Ming Chang⁴, Chuang-Yi Liao⁴, Yu-Tang Hsiao⁴, Chung-Hao Chen^{1

2}, Yu-Che Lin^{1

2}, Shih-Yu Huang^{1

2}, Bin Chang^{1

2}, Yang Yang⁵, Chih-Wei Chu^{3

6}, Kung-Hwa Wei^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu 3001, Taiwan.
² Department of Materials Science and Engineering, Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu 3001, Taiwan.
³ Research Center for Applied Science, Academia Sinica, Taipei 115, Taiwan.
⁴ Raynergy Tek Incorporation, 2F, No. 60, Park Avenue 2, Hsinchu Science Park, Hsinchu 30844, Taiwan.
⁵ Department of Materials Science and Engineering, California NanoSystems Institute, University of California, Los Angeles, California 90095, United States.
⁶ College of Engineering, Green Technology Research Center, Chang Gung University, Taoyuan City, 33302 Taiwan, ROC.

PMID: 34096256
DOI: 10.1021/acsami.1c06762

Abstract

In this study, we prepared organic photovoltaics (OPVs) featuring an active layer comprising double bulk heterojunction (BHJ) structures, featuring binary blends of a polymer donor and concentration gradients of two small-molecule acceptors. After forming the first BHJ structure by spin-coating, the second BHJ layer was transfer-printed onto the first using polydimethylsiloxane stamps. A specially designed selenium heterocyclic small-molecule acceptor (Y6-Se-4Cl) was employed as the second acceptor in the BHJ. X-ray photoelectron spectroscopy revealed that the two acceptors formed a gradient concentration profile across the active layer, thereby facilitating charge transportation. The best power conversion efficiencies (PCEs) for the double-BHJ-structured devices incorporating PM6:Y6-Se-4Cl/PM6:Y6 and PM6:Y6-Se-4Cl/PM6:IT-4Cl were 16.4 and 15.8%, respectively; these values were higher than those of devices having one-BHJ structures based on PM6:Y6-Se-4Cl (15.0%), PM6:Y6 (15.4%), and PM6:IT-4Cl (11.6%), presumably because of the favorable vertical concentration gradient of the selenium-containing small-molecule Y6-Se-4Cl in the active layer as well as some complementary light absorption. Thus, combining two BHJ structures with a concentration gradient of the two small-molecule acceptors can be an effective approach for enhancing the PCEs of OPVs.

Keywords: acceptor gradient concentration; double bulk heterojunction; heteroatoms; organic photovoltaics; selenium; transfer printing; vertical-gradient concentration.