Enhancing Indacenodithiophene Acceptor Crystallinity via Substituent Manipulation Increases Organic Solar Cell Efficiency

• DOI: 10.1021/acs.chemmater.7b04616
• Publication Date: 2017-11-28T01:22:49Z
• Authors: Thomas J. Aldrich; Steven M. Swick; Ferdinand S. Melk...; Tobin J. Marks
• Keywords: 01 natural sciences; 7. Clean energy; 0104 chemical sciences

The post-fullerene indacenodithiophene acceptor ITIC is a highly effective n-type component of high-performance bulk-heterojunction (BHJ) polymer solar cells (PSCs) for reasons that are not well-understood. Here, the impact of the ITIC alkyl sub-stituent architecture on PSC active layer film morphology, charge transport, and photovoltaic (PV) performance is investigated with the donor polymers PBDB-T and PBDB-TF. On progressing from n-propyl to n-hexyl to n-nonyl ITIC substituents, PSC power conversion efficiency (PCE) increases from <0.1 % to 9.31% to 10.24%, respectively. BHJ blend morphology, carrier recombina-tion dynamics, and PV performance with both donor polymers as probed by AFM, XRD, GIWAXS, and light intensity dependence correlate with marked differences in ITIC acceptor crystallinity. The DSC cold crystallization temperatures of the n-hexyl and n-nonyl-functionalized acceptors are found to closely track the anneal-ing temperatures for optimum PSC performance. These results identify a promising...