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An Efficient Tin‐Free Route to Small Molecules Based on Silole‐Modified Pentathiophenes for Solution‐Processed Organic Solar Cells

2014; Wiley; Volume: 3; Issue: 9 Linguagem: Inglês

10.1002/ajoc.201402106

2193-5815

Qingcai Yu, Weifei Fu, Hongyu Wang, Xiaofeng Wu, Jun‐Hua Wan, Minmin Shi, Hongzheng Chen,

Perovskite Materials and Applications

Abstract A acceptor–donor–acceptor (A–D–A) molecule based on a silole‐modified pentathiophene (SiPTA) electron‐donor unit and two diketopyrrolopyrrole (DPP) acceptor units, DPP 2 (SiPTA), was designed and synthesized. An unsymmetrical molecule with D–A structure, DPP‐SiPTA, was also synthesized for comparison. Both molecules were synthesized using an environmentally friendly Suzuki coupling protocol, which was modified to avoid ring‐opening of the silole under basic conditions. The D–A design has an obvious effect on the electronic structure of these compounds. The D–A–D‐structured DPP 2 (SiPTA) has a much lower band gap and HOMO than D–A‐structured DPP‐SiPTA. Furthermore, the molecular symmetry significantly influenced crystallinity. Organic solar cells (OSCs) based on DPP 2 (SiPTA)/PC 71 BM (1:5, w/w; PC 71 BM=[6,6]‐phenyl C 71 ‐butyric acid methyl ester) have a power conversion efficiency of 2.36 % with an open‐circuit voltage of up to 0.84 V, which, as expected, is much higher than that of the recently reported OSCs based on DPP 2 (NPTA) (0.71 V), in which pyrrole‐modified pentathiophene (NPTA) is the donor unit.