Influence of counter-anions during electrochemical deposition of ZnO on the charge transport dynamics in dye-sensitized solar cells

Abstract

Porous ZnO/EosinY films have been electrochemically deposited by oxygen reduction in the presence of a zinc salt from EosinY-containing aqueous solutions, with either chloride or perchlorate as the counter anion. EosinY was removed and the films were sensitised by D149. These electrodes were used for dye-sensitised solar cells (DSCs), and charge transport in the porous network was studied by intensity modulated current/voltage spectroscopy (IMVS/IMPS) and electrochemical impedance spectroscopy (EIS) under illumination. Doping of ZnO during the electrodeposition could be proven by changes in the charge transport in ZnO and could be shown to occur when chloride was used as the counter ion. By using perchlorate as the counter ion, on the other hand, a more reproducible occupation of trap levels was obtained at, however, slightly lower voltages in DSCs whose origin is discussed in detail.

Metal Complexes as Redox Shuttles in Dye-Sensitized Solar Cells Based on Electrodeposited ZnO: Tuning Recombination Kinetics and Conduction Band Energy

“…24 In brief, a 600 nm thick compact ZnO layer was deposited on pre-cleaned ZnO:Al substrates (Kaivo, < 10 −1 ) by applying a constant potential of −1.06 V versus an Ag/AgCl reference electrode (REF210 Red Rod, Radiometer analytical) for 10 min in presence of a Pt wire as counter electrode. The substrates were attached to a rotating disk electrode (500 rpm, BELLTEC) in contact to an aqueous solution (70…”

Efficient Electron Collection by Electrodeposited ZnO in Dye-Sensitized Solar Cells with TEMPO+/0 as the Redox Mediator

“…The τ tr -values for both nanoparticulate TiO 2 and electrodeposited ZnO are in a range that is typically observed for both materials. ,− Fast recombination of electrons from the semiconductor to the TEMPO + species leads to a significantly lower τ n than for other redox couples such as I 3 – /I – or [Co­(bpy) 3 ] 3+/2+ . , As evident from Figure c, electron recombination occurs at about the same rate for TiO 2 and ZnO. However, because of the much faster transport of electrons through the highly crystalline electrodeposited ZnO electrode, τ n > τ tr is still fulfilled and leads to efficient charge collection and, consequently, a high EQE and j sc , unlike for the nanoparticulate TiO 2 photoelectrode.…”

“…A compact ZnO-underlayer (ZnO-UL) was electrodeposited from an oxygen-saturated, aqueous zinc salt solution onto cleaned aluminum-doped zinc oxide (AZO)-coated glass substrates (Kaivo, <10 Ω □ –1 ), followed by the electrodeposition of a porous ZnO film from the same solution with the addition of 50 μM eosin Y (Chemplex, >88%). The process was carried out as described in detail previously. ,, The porous film covered a circular area with diameter 0.6 cm (0.283 cm 2 ). The compact ULs and the porous films had a thickness of roughly 0.6 and 2.7 μm as determined by profilometry, respectively.…”

“…The process was carried out as described in detail previously. 37,41,42 The porous film covered a circular area with diameter 0.6 cm (0.283 cm 2 ). The compact ULs and the porous films had a thickness of roughly 0.6 and 2.7 μm as determined by profilometry, respectively.…”

Charge transfer at organic-inorganic interfaces

“…The layer is prepared by applying a TiO 2 -gel and sintering at 450 • C. Mesoporous ZnO was prepared by an electrochemical deposition of ZnO on FTO glass in the presence of a structure-directing agent, using KCl as electrolyte component. The deposited film was left overnight in an aqueous KOH solution to remove the structure-directing agent and dried before the sensitization (see 17 for experimental details). Indoline dye layers were prepared by drop casting the same solution as used for soaking on flat substrates, i.e., on single crystals of ZnO(0001), rutile TiO 2 (100), and SiO 2 (0001) (Crystec) as well as on standard fused silica.…”