The synthesis and photovoltaic performance of regioregular poly[3-(n-butoxymethyl)thiophene]

The synthesis and photovoltaic performance of poly [3-(n-butoxymethyl)-thiophene] (P3BMT) is reported. Incorporation of a n-butoxymethyl side chain, instead of an alkyl chain as in poly(3-hexylthiophene) (P3HT) may increase the oxidation potential via an inductive effect, leading to an increase in open-circuit voltage (V,,) in bulk heterojunction solar cells. Applying the Grignard metathesis polymerization route afforded highly regioregular P3BMT with > 95% HT coupling. In solution, the optical and electrochemical properties of P3BMT are nearly identical to those of P3HT. However, the absorption data in the film point to a lesser degree of 3D ordering. The ether functionality appears to prevent a close packing of the chains. The best bulk heterojunction solar cells made from P3BMT with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) as acceptor had V-oc=0.71 V, which is indeed similar to 0.1 V higher than that of P3HT:PCBM cells. As a result of the lower 3D ordering, the short-circuit current (J(sc)=4.16 mA/cm(2)) is less. In combination with a fill factor of 0.57, a maximum power conversion efficiency of 1.68% was obtained. (c) 2007 Elsevier B.V. All rights reserved.