Triphenylimidazole Based Dye-Sensitized Solar Cells for Efficient Solar and Artificial Light Conversion using Iodide/Triiodide Redox Electrolyte

Though metal complex-based redox couples showed promising results in test cell devices of dye-sensitized solar cells (DSSCs), it hampers the scale-up of modules/panels due to mass transport and recombination issues. Copper (II/I) redox couple-based DSSCs have dispensed exceptional results at diffused/artificial indoor light conditions as potential candidates for Internet of Things (IoT) applications. Recently, our group have reported triphenylimidazole based metal-free organic dyes (LG-P series) with [Cu(tmby)₂]^2+/+ (tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine) redox couple realizing device efficiency of ~10% under low-light conditions. In the present study, we extended the work using iodide-triiodide (I⁻/I₃⁻) redox couple with LG-P series of sensitizers and measured the device efficiencies under both full sun (100 mW/cm²) and low-light conditions (1000 lux indoor illumination). Under full sun condition, LG-P3 has delivered a power conversion efficiency (PCE) of 2.15%, whereas at 1000 lux daylight, LED LG-P1 showed a PCE of 10.53%, and at 1000 lux daylight CFL LG-P3 showed PCE of 9.19%, which we observed with I⁻/I₃⁻ redox electrolyte. We have adopted charge extraction (CE), open-circuit voltage decay (OCVD) and electrochemical impedance spectroscopy (EIS) to explain the efficiency differences in LG-P series of dyes.

Graphical abstract

Mass transport and recombination are two hurdles for metal complex-based redox couples for dye-sensitized solar cells. We have fabricated DSSC devices using triphenylimidazole-based organic dyes with I⁻/I₃⁻ redox electrolyte and measured its device efficiency under full sun and artificial/indoor light conditions and the potential for the Internet of Things (IoT) applications.