title: Effect of the co-sensitization sequence on the performance of dye-sensitized solar cells with porphyrin and organic dyes.
abstract: To obtain a broad spectral response in the visible region, TiO2 film is co-sensitized with a porphyrin dye (FNE57 or FNE59) and an organic dye (FNE46). It is found that the stepwise co-sensitization in one single dye solution followed by in another single dye solution is better than the co-sensitization in a cocktail solution in terms of photovoltaic performance. The stepwise co-sensitization first with a porphyrin dye and then with an organic dye outperforms that in a reverse order. DSSC devices based on co-sensitizers FNE57 + FNE46 and FNE59 + FNE46 with a quasi-solid-state gel electrolyte generate power conversion efficiencies of 7.88% and 8.14%, respectively, which exhibits remarkable efficiency improvements of 61% and 35%, as compared with devices sensitized with the porphyrin dyes FNE57 and FNE59, respectively. Co-sensitization brings about a much improved short-circuit photocurrent due to the complementary absorption of the two sensitizers. The observed enhancement of incident monochromatic photon-to-electron conversion efficiency from individual dye sensitization to co-sensitization is attributed to the improved charge collection efficiency rather than to the light harvesting efficiency. Interestingly, the open-circuit photovoltage for the co-sensitization system comes between the higher voltage for the porphyrin dye (FNE57 or FNE59) and the lower voltage for the organic dye (FNE46), which is well correlated with their electron lifetimes. This finding indicates that not only the spectral complementation but also the electron lifetime should be considered to select dyes for co-sensitization.
authors.affiliation: Department of Chemistry, Lab of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai 200438, P. R. China. zs.wang@fudan.edu.cn and School of Chemistry & Material Engineering, Fuyang Normal College, Fuyang, Anhui 236037, P. R. China.
authors.forename: Suhua
authors.initials: S
authors.lastname: Fan
authors.affiliation: Department of Chemistry, Lab of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai 200438, P. R. China. zs.wang@fudan.edu.cn.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Chemistry, Lab of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai 200438, P. R. China. zs.wang@fudan.edu.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Chemistry, Lab of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai 200438, P. R. China. zs.wang@fudan.edu.cn.
authors.forename: Gang
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Department of Chemistry, Tung Hai University, NO. 1727, Sec.4, Taiwan Boulevard, Xitun District, Taichung, Taiwan 40704, P. R. China.
authors.forename: Yuan Jay
authors.initials: YJ
authors.lastname: Chang
authors.affiliation: Department of Chemistry, Lab of Advanced Materials, Collaborative Innovation Center of Chemistry for Energy Materials, Fudan University, Shanghai 200438, P. R. China. zs.wang@fudan.edu.cn.
authors.forename: Zhong-Sheng
authors.initials: ZS
authors.lastname: Wang