Solar Cells Constructed with Polythiophene Thin Films Grown along Tethered Thiophene-Dye Conjugates via Photoelectrochemical Polymerization

A polythiophene-based solar cell (PTSC) is constructed by photoelectrochemically polymerizing thiophene onto an ultrathin compact TiO2 layer (150 nm thick) covered with a sub-monolayer of tethered 3-(5-[N,N-bis(4-diphenylamino)phenyl]thieno[3,2-b]thiophen-2-yl}-2-cyano-acrylic acid dye (ca. 10% coverage). The influence of morphology and thickness of the PT film on the photocurrent generated by the PTSC was investigated. With a 270 nm thick PT film and 2,2',7,7'-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9'-spirobifluorene serving as the hole-transport material, the PTSC exhibited a short-circuit current density J(SC) of 12.90 +/- 0.63 mA/cm(2), an open-circuit voltage V-OC of 0.81 +/- 0.01 V, and a fill factor of 0.72 +/- 0.01. The high conversion efficiency (7.52 +/- 0.58%) of the PTSC is attributed to the controlled PT growth along the ordered and spatially accessible dye molecules at the compact TiO2 layer, which facilitates charge transfer, prevents the hole/electron recombination, and simplifies the polymer solar cell construction with a stable and easily processable material.