| 초록 |
Dithieno[3,2-b:2’,3’-d]silole (DTS) has been used as an attractive electron-rich unit of donor-acceptor type conjugated copolymers for polymer solar cells, because it improves the crystallinity and hole mobility owing to rigid coplanar structure and the bridging atom of Si instead of C. However, DTS-based polymers have exhibited a relatively high HOMO energy level due to its strong electron donating ability, causing a low VOC in solar cell devices. In this work, for the purpose to improve the VOC, we introduced 2,7-dibenzosilole (DBS) as an electron-rich unit which has a weaker electron donating ability than DTS, and synthesized a low bandgap polymer (PDBSDTBO) composed of DBS as an electron-rich unit and alkoxy substituted 1,2,5-benzooxadiazole as an electron-deficient unit. The HOMO energy level of PDBSDTBO (‒5.5 eV) is much deeper than that of PDTSDTBO (‒5.0 eV), and therefore PDBSDTBO exhibits much higher VOC (0.93 V) of the solar cell device than that of PDTSDTBO (0.64 V). |
