Spatial separation strategies to control charge recombination and dye regeneration in p-type dye sensitized solar cells

• Published in: Solar energy 2022-04, Vol.236, p.107-152
• Main Authors: Daoud, Adel, Cheknane, Ali, Meftah, Afek, Michel Nunzi, Jean, Shalabi, Manal, Hilal, Hikmat S.
• Format: Article
• Language: English
• Subjects: Charge recombination; Charge separation; Competition; Design; Dye-sensitized solar cells; Dyes; Electrodes; Electrolytes; Electrolytic cells; Holes (electron deficiencies); Kinetic competition; Manufacturing; Molecular structure; Nickel oxides; p-DSSC; Photovoltaic cells; Photovoltaics; Production methods; Recombination; Recombination reactions; Regeneration; Semiconductor materials; Separation; Solar cells; Solar energy; Spatial separation
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2022.02.050

[Display omitted] •p-NiO attracts special attention as a working electrode in p-DSSCs.•Spacers in dyes inhibit various recombination types and improve performance in p-DSSCs.•p-DSSC performance improves with dye HOMO level lower than NiO Valence Band.•Dye LUMO should be higher than Redox couple potential for higher p-DSSC performance.•Aluminum-doped zinc oxide is recommended in p-DSSCs. Dye-sensitized-solar cells, DSSCs, are emerging as alternatives to traditional photovoltaic solar cells. Among them, p-type DSSCs attracted special attention due to their easy manufacturing methods, understandable operating mechanisms and friendliness to environment. In these solar cells, the fate of the excited electron is determined based on the kinetic competition that occurs between two processes: electron-hole charge separation and recombination processes. Additionally, the type of the electrolyte is responsible for another competition, namely between recombination reactions and the dye regeneration by the electrolyte. Early studies showed that p-DSSCs and n-DSSCs may be combined to create tandem solar cells (t-DSSCs). Nonetheless, the performance is normally very poor due to the above-mentioned competing processes, which dictates the need to improve DSSCs. Various semiconductor materials were described in manufacturing the working electrodes in DSSCs, among which NiO is the most common material. Therefore, special attention is paid to NiO as a working electrode (WE) here. Effects of sensitizer, redox couple and the transparent conducting oxide electrode with NiO electrode on the cell performance are discussed here with useful recommendations. Inserting spacers in the dye molecular structure can improve cell performance by improving dye regeneration and inhibiting charge recombination, as widely described. However, the effect of spatial separation within the dye has not been specifically reviewed earlier, and this review article is mainly devoted to such effect within the frameworks of spatial separation strategy. Sensitizer molecule aggregations are also discussed, with techniques to optimize dye loading without aggregation.