Silaindacenodithiophene‐Based Fused‐Ring Non‐Fullerene Electron Acceptor for Efficient Polymer Solar Cells

• Published in: Chinese journal of chemistry 2018-06, Vol.36 (6), p.495-501
• Main Authors: Nian, Yaowen, Wang, Zhen, Jiang, Haiying, Feng, Shizhen, Li, Suhan, Zhang, Lianjie, Cao, Yong, Chen, Junwu
• Format: Article
• Language: English
• Subjects: Absorption; Bridge construction; Circuits; Construction standards; Energy conversion efficiency; Energy levels; Malononitrile; Molecular chains; Molecular orbitals; nonfullerene acceptor; Photovoltaic cells; polymer solar cells; Polymers; silaindacenodithiophene; Solar cells; thermal annealing
• ISSN: 1001-604X; 1614-7065
• DOI: 10.1002/cjoc.201700809

In this work, a new A‐D‐A type nonfullerene small molecular acceptor SiIDT‐IC, with a fused‐ring silaindacenodithiophene (SiIDT) as D unit and 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (INCN) as the end A unit, was design and synthesized. The SiIDT‐IC film shows absorption peak and edge at 695 and 733 nm, respectively. The HOMO and LUMO of SiIDT‐IC are of −5.47 and −3.78 eV, respectively. Compared with carbon‐bridging, the Si‐bridging can result in an upper‐lying LUMO level of an acceptor, which is benefit to achieve a higher open‐circuit voltage in polymer solar cells (PSCs). Complementary absorption and suitable energy level alignment between SiIDT‐IC and wide bandgap polymer donor PBDB‐T were found. For the PBDB‐T:SiIDT‐IC based inverted PSCs, a D/A ratio of 1: 1 was optimal to achieve a power conversion efficiency (PCE) of 7.27%. With thermal annealing (TA) of the blend film, a higher PCE of 8.16% could be realized due to increasing of both short‐circuit current density and fill factor. After the TA treatment, hole and electron mobilities were elevated to 3.42 × 10−4 and 1.02 × 10−4 cm2·V−1·s−1, respectively. The results suggest that the SiIDT, a Si‐bridged fused ring, is a valuable D unit to construct efficient nonfullerene acceptors for PSCs. Silaindacenodithiophene (SiIDT), a Si‐bridged fused ring, is introduced to construct a new narrow band gap non‐fullerene acceptor. Its polymer solar cells combining a well‐known PBDB‐T donor can show a power conversion efficiency up to 8.16%.