A Near-IR Absorbing Copolymer for Nanoarchitected Solution-Processable Photovoltaic Devices: Synthesis and Application

A novel low bandgap copolymer based on dithienosilole and pyridalthiadiazole (PDTSDTPT) is synthesized via Stille cross coupling. Its chemical, thermal, optical, electrical, and elctrochemical properties were investigated. We evidenced by UV-vis Spectroscopy that PDTSDTPT with modulated HOMO and LUMO energy levels exhibit higher absorptions over a larger fraction of the solar spectrum than the BT analogue with an absorbance that reaches around 900 nm in the infrared region. The photovoltaic applicability of this specific polymer was confirmed by preliminary tests in devices based on bulk heterojunction (BHJ) employing PC60BM, [6,6]-phenyl-C-60 butyric acid methyl ester, as the n-type semiconductor under irradiance of 100 mW cm(-2). The results indicate that despite the low mobility of PC60BM and without control of the morphology, PDTSDTPT show promising improvable performances. Open circuit voltage (V-OC) close to 0.7 V, short circuit current (J(SC)) close to 4.6 mA cm(-2) and power conversion efficiency (PCE) of 1.2% were obtained. However, in current work, we expect that further improvement of device performance will be achieved via the substitution of PC60BM by semi-conducting carbon nanotubes (s-SWNT) in the photoactive layer that should increase the charge mobility and enhance the device performance.