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/cm2, 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.