Synthesis and photovolatic properties of new poly(quarterselenophene) and poly(quarterselenophene-alt-quarterthiophene)s

Poly [3,3′-didodecylquaterselenophene] (PQS) and poly[3,3′- didodecylquaterselenophene-alt-didodecylquaterthiophene] (PQSQT), have been synthesized by using a Stille cross-coupling reaction. The weight-averaged molecular weights (M_w) of PQS and PQSQT were found to be 18,900 Da and 22,300 Da with polydispersity indices of 1.71 and 1.99, respectively. Photophysical measurements found the low bandgaps of 1.73 eV for PQS and 1.86 eV for PQSQT. The field-effect mobilities of PQS and PQSQT were determined to be 6.0×10^-3 and 0.05 cm²/V s, respectively. The influence of the selenium and sulfur atoms in the polymer backbones were investigated with regard to device performances. The polymers were combined with the PC₇₁BM ([6,6]-phenyl C₇₁-butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells with power conversion efficiencies of 0.73-2.37% under AM 1.5 G (100 mW/cm²) conditions.