Photovoltaic characterization of poly(2,5-bis(3-dodecylthiophen-2-yl)-2′,2″-biselenophene) for organic solar cells

A novel regioregular selenophene and thiophene-based poly(2,5-bis(3-dodecylthiophen-2-yl)-2′,2″-biselenophene) (PBTBS), was chosen as promising electron donor materials blended with [6,6]-phenyl-C61 butyric acid methyl ester(PCBM) to fabricate bulk heterojunction solar cells. The optical and photovoltaic properties of PBTBS were characterized and compared to those of poly(3,3″′-didedocyl-quaterthiophene)( PQT-12). The PBTBS showed a higher ionization potential (IP) and improved oxidative stability than PQT-12 through the cyclic voltammetry (CV) measurements, which was due to stronger electron-donating properties of selenophene than that of thiophene analogue. A comparison of photovoltaic properties of cells between two polymer donors PBTBS and PQT-12 were also carried out. The result showed that cells based on the PBTBS had the comparable photovoltaic parameters with those of the PQT-12. An open voltage (V_OC) of 0.46 V, a short-circuit current (J_SC) of 0.17 mA/cm², a fill factor (FF) of 0.32 and a power conversion efficiency (η) of 0.34% were achieved at 100 mW/cm² (AM 1.5). The external quantum efficiency of cells based on the PBTBS exhibited much better performance with around 3.4% at 540 nm compared with that of the PQT-12.