Theoretical and photovoltaic investigations of 1,3,5-triazine-based photosensitizers achieving highly efficient DSSCs

Abstract By establishing a new push-pull relationship, three novel metal-free organic sensitizers based on A'–π–A framework were synthesized, in which A' and A represent the auxiliary acceptor (triazine) and the main acceptor (cyanoacrylic acid), respectively, coded ZS03, ZS04, and ZS05. In this paper, the molecular structure, photophysical property, electrochemical property, theoretical calculation, and photovoltaic property of these three sensitizers are described in detail. The results show that the additional acceptor and alkyl chains significantly affect the molecule’s energy level and spatial structure. In terms of photovoltaic characteristics, the ZS03-based device exhibits the best power conversion efficiency (PCE) of 7.11%, corresponding to a short-circuit photocurrent density (Jsc) of 14.31 mA cm−2, an open-circuit voltage (Voc) of 708 mV, and a fill factor (FF) of 0.723, which is the highest efficiency among the known A'–π–A type dyes. It can be determined that the improvement of PCE is mainly due to the combination of the following two factors: the π-spacer with appropriate length and the alkyl chain with a reasonable layout.