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

Abstract

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 − /I 3 − ) 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 − /I 3 − cells yielded 9.0% 1 Sun PCE and 23.1% of PCE under 1000 lx. Optimized [Co(bpy) 3 ] 3+/2+ and I − /I 3 − 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.

Top-ranked efficiency under indoor light of DSSCs enabled by iodide-based DES-like solvent electrolyte

“…In particular, PTZ-Th-C 8 sensitized cells filled with solution 3 and PTZ-TTh-C 6 sensitized cells filled with solution 4 offered the best performance, with PCE reaching the remarkable value of 8%. These results are just slightly lower than that of VOC-based cells with similar characteristics (similar power input, no co-sensitization, and I − /I 3 − based electrolyte), 79 and outmatch the only example reported in the literature for VOC-free water-based DSSCs under ambient light. 75 Once again, the ChI/EG electrolyte showed superior performances compared to the ChCl/EG counterpart.…”

“…30 mW cm −2 , which compare well with literature values. 75,79,81 Such power quantities well match the power required by small electronic appliances, 23,82 such as TV remote controls, for a 4 cm 2 device area, and small wireless sensors.…”

Solid‐State Monolithic Dye‐Sensitized Solar Cell Exceeding 10% Efficiency Using a Copper‐Complex Hole Transport Material and a Carbon Counter‐Electrode

“…Better PCEs should be possible to reach if the devices are optimized specifically for artificial illumination. [ 51 ] Long‐term operational stability is another crucial parameter to evaluate the practical implementation of these devices. Figure displays the photovoltaics metrics vs. time for solid‐state M ‐DSSCs under artificial light soaking.…”

“…The solution used for the spray pyrolysis was composed of anhydrous 2‐propanol (7.0 mL), of titanium diisopropoxide bis(acetylacetonate) (0.6 mL), and of acetylacetone (0.4 mL); the compact layer of TiO 2 was sintered at 450 °C for 45 min. A mesoporous TiO 2 layer (circular shape with an area of 0.126 cm 2 ) was deposited by screen printing and annealed for 1 h at 500 °C; the 18NR‐T titania paste, composed of particles with an average particle size of 20 nm, [ 51 ] was diluted in α‐terpineol in the ratio 2:1 (titania:α‐terpineol), which formed a mesoporous TiO 2 layer with a thickness of 4.5 ± 0.5 μm ( Figure a). The TiO 2 layer was dipped in a TiCl 4 aqueous solution (53 mM; 70 °C; 30 min), then sintered at 500 °C for 1 h. After the treatment with TiCl 4 , a spacer layer made of TiO 2 ‐rutile paste (WER2‐O), diluted in α‐terpineol in the ratio 2:1 (titania:α‐terpineol), was screen printed over the mesoporous layer and annealed at 500 °C for 1 h, resulting in an active TiO 2 layer with a thickness of 4.5 ± 0.5 μm (Figure 11b).…”

“…The WER2‐O TiO 2 paste is composed of a blend of anatase and rutile particles, with sizes of 20 nm up to 450 nm. [ 51 ] The morphology of the TiO 2 mesoporous and TiO 2 spacer layers was studied by SEM (Figure S8, Supporting Information). The counter‐electrode, composed of GCB paste (Elcocarb B/SP), was deposited by screen‐printing atop the spacer layer and annealed for 45 min at 420 °C to form a 23 ± 3 μm carbon layer (Figure 11c).…”