Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 23, Pages 27227-27236Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c06762
Keywords
organic photovoltaics; double bulk heterojunction; vertical-gradient concentration; acceptor gradient concentration; selenium; heteroatoms; transfer printing
Funding
- Center for Emergent Functional Matter Science of the National Yang Ming Chiao Tung University
- National Chiao Tung University from the Featured Areas Research Center Program
- Ministry of Science and Technology, Taiwan [MOST 106-2221-E-009-132-MY3]
- Ministry of Science and Technology (MOST) of Taiwan [107-2221-E-001-007-MY3]
- Sustainability Science Research Program, Academia Sinica, Taiwan [AS-SS-108-04, AS-SS-109-05]
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This study focused on preparing organic photovoltaics (OPVs) with double bulk heterojunction (BHJ) structures, incorporating two small-molecule acceptors with concentration gradients to enhance charge transportation and power conversion efficiencies. The results showed that devices with the double-BHJ structure had higher PCEs compared to those with single-BHJ structures, highlighting the effectiveness of combining two BHJ structures with a concentration gradient of small-molecule acceptors for improving OPV performance.
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.
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