Abstract
We report the synthesis and characterization of new metal-free organic dyes (namely B18, BTD-R, and CPTD-R) which designed with D-π-A concept to extending the light absorption region by strong conjugation group of π-linker part and applied as light harvester in dye sensitized solar cells (DSSCs). We compared the photovoltaic performance of these dyes in two different photoanodes: a standard TiO2 mesoporous photoanode and a ZnO photoanode composed of hierarchically assembled nanostructures. The results demonstrated that B18 dye has better photovoltaic properties compared to other two dyes (BTD-R and CPTD-R) and each dye has higher current density (Jsc) when applied to hierarchical ZnO nanocrystallites than the standard TiO2 mesoporous film. Transient photocurrent and photovoltage decay measurements (TCD/TVD) were applied to systematically study the charge transport and recombination kinetics in these devices, showing the electron life time (τR) of B18 dye in ZnO and TiO2 based DSSCs is higher than CPTD-R and BTD-R based DSSCs, which is consistent with the photovoltaic performances. The conversion efficiency in ZnO based DSSCs can be further boosted by 35%, when a compact ZnO blocking layer (BL) is applied to inhibit electron back reaction.
Highlights
Triphenyl amine donor, gained popularity because of the prominent performance in Dye sensitized solar cells (DSSCs) devices
The transient photocurrent and photovoltage decay (TCD/transient voltage decay (TVD)) results demonstrated that device with B18 dye has better τR and negligible shift in the conduction band (CB) of dye sensitized photoanodes as compared to CPTD-R and BTD-R dyes based devices
Each dye results in higher Jsc in hierarchical structured ZnO than in standard mesoporous TiO2, mainly due to better electron transport properties featured by hierarchical structured ZnO nanocrystallites compared to TiO2
Summary
Triphenyl amine donor, gained popularity because of the prominent performance in DSSC devices. Since all the other components of the cells (photoanode, electrolyte and counter electrode) are the same, the difference in functional performances is mainly dependent on the properties of dye molecules such as: (i) electron injection efficiency (position of LUMO level with respect to the CB of semiconductor); (ii) oxidized dye regeneration efficiency (position of HOMO level with respect to standard redox potential of I−/I3−); (iii) light harvesting efficiency (γ LHE).
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