Molecular design of metal-free D-pi-A substituted sensitizers for dye-sensitized solar cells by Alibabaei, L, Kim, J, Wang, M, Pootrakulchote, N, Teuscher, J, Di Censo, D, Humphry-Baker, R, Moser, J, Yu, Y, Kay, K, Zakeeruddin, S, Graetzel, M