科研之友
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摘要
Designing electron-deficient unit based on fused ring is an effective strategy for constructing high-performance conjugated copolymers. In this work, a new electron-deficient monomer (DTPZ) with 9,10-difluorodithienophenazine as the core was synthesized, and two new polymers PB-DTPZ and PFB-DTPZ were prepared. The photo. physical properties, electrochemical properties, and organic photovoltaic performance of the two polymers as well as their active layer morphologies were studied and analyzed. Polymers PB-DTPZ and PFB-DTPZ possess optical band gaps of 1.70 and 1.68 eV, respectively, showing red-shifted absorption spectra compared with common wide band gap polymers. The PB-DTPZ and PFB-DTPZ also show low-lying HOMO energy levels of -5.51 and -5.68 eV, respectively, suggesting the electron-deficient feature of DTPZ. Thanks to the more matched HOMO energy level to Y6 acceptor, the PB-DTPZ:Y6-based binary polymer solar cell can achieve a power conversion efficiency (PCE) of 12.13%, which is higher than that (10.4%) of the PFB-DTPZ:Y6-based binary device. Due to the deeper HOMO levels and complementary absorption spectra of PB-DTPZ and PFB-DTPZ, the addition of the two polymers as the third component to the PM6:Y6 system can further improve the PCE, and the resulting ternary devices can deliver PCEs of 17.08% and 16.99%, respectively.
