An investigation into the origin of variations in photovoltaic performance using D–D–π–A and D–A–π–A triphenylimidazole dyes with a copper electrolyte

The potential of using non-planar triphenylimidazole-donor-based dyes in dye-sensitized solar cells was explored via synthesizing two novel dyes, LG-P1 and LG-P3, with D–D–π–A and D–A–π–A architectures, respectively. Anthracene and benzothiadiazole were used as the auxiliary donor and auxiliary acceptor units, respectively, in these newly designed sensitizers. The dyes were custom-designed to have a more positive ground state potential to make them compatible with a new-generation alternative copper electrolyte, [Cu(dmp)2]1+/2+. We investigated various factors contributing to the variations in the photovoltaic performance upon the use of triphenylimidazole dyes with different auxiliary donor and acceptor units with [Cu(dmp)2]1+/2+ electrolyte. Based on our observations, the triphenylimidazole dye having D–A–π–A architecture with benzothiadiazole as the auxiliary acceptor unit delivered better photovoltaic performance than the dye with anthracene as an auxiliary donor with D–D–π–A architecture. Electrical and optical perturbation methods were used to systematically probe the charge transfer and transport behaviours at the interfaces when employing these sensitizers.