Abstract
Chlorophyll a derivatives were integrated in "all solid-state" dye sensitized solar cells (DSSCs) with a mesoporous TiO 2 electrode and 2 ,2 ,7,7-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9-spirobifluorene as the hole-transport material. Despite modest power conversion efficiencies (PCEs) between 0.26% and 0.55% achieved for these chlorin dyes, a systematic investigation was carried out in order to elucidate their main limitations. To provide a comprehensive understanding of the parameters (structure, nature of the anchoring group, adsorption. . .) and their relationship with the PCEs, density functional theory (DFT) calculations, optical and photovoltaic studies and electron paramagnetic resonance analysis exploiting the 4-carboxy-TEMPO spin probe were combined. The recombination kinetics, the frontier molecular orbitals of these DSSCs and the adsorption efficiency onto the TiO 2 surface were found to be the key parameters that govern their photovoltaic response.