Conventional and Back-Illuminated Cobalt- and Iodine-Mediated Dye-Sensitized Solar Cells for Artificial and Solar Light Conversion

Dye-sensitized solar cells (DSSCs) are among the leading PV technologies for indoor applications. These devices need to be optimized for these illumination conditions since, as it will be demonstrated, the best devices under solar conditions do not originate from the best devices under artificial illumination. This work studies the impact of the photoanode thickness, its light-scattering properties, dye loading, distance from the photoelectrode to the counter electrode on the charge transfer, recombination, and photovoltaic response of cobalt (III/II) bipyridine ([Co(bpy)3] 3+/2+) and iodide/triiodide (I–/I3–) DSSCs under 1 Sun and artificial 1000 lx light illumination. The champion [Co(bpy)3] 3+/2+ device displayed a power conversion efficiency (PCE) of 11.0 and 32.0% under AM1.5G and 1000 lx, respectively. The best I–/I3– cells yielded 9.0% 1 Sun PCE and 23.1% of PCE under 1000 lx. Optimized [Co(bpy)3]3+/2+ and I–/I3– DSSCs demonstrated huge potential as efficient indoor-photovoltaics and can straightforwardly be used as back-illuminated devices to improve the output power under low illumination. Under 1000 lx room light, the champion cobalt DSSCs displayed a record PCE of 27.3% from the rear-side with 85.3% of retention ratio.