Hydroquinone redox mediator enhances the photovoltaic performances of chlorophyll-based bio-inspired solar cells

• Published in: Communications chemistry Vol. 4; no. 1; pp. 118 - 10
• Main Authors: Duan, Shengnan, Uragami, Chiasa, Horiuchi, Kota, Hino, Kazuki, Wang, Xiao-Feng, Sasaki, Shin-ichi, Tamiaki, Hitoshi, Hashimoto, Hideki
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.08.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 639/638/439/946; 639/638/440/527/1820; 639/638/440/947; 639/638/440/949; 639/638/440/950; Absorption spectroscopy; Anions; Biodegradability; Biomimetics; Carotene; Cations; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Chlorophyll; Deoxygenation; Energy conversion efficiency; Excitation; Hydroquinone; Photoelectricity; Photosynthesis; Photovoltaic cells; Solar cells; Spectrum analysis
• ISSN: 2399-3669; 2399-3669
• DOI: 10.1038/s42004-021-00556-5

Chlorophyll (Chl) derivatives have recently been proposed as photoactive materials in next-generation bio-inspired solar cells, because of their natural abundance, environmental friendliness, excellent photoelectric performance, and biodegradability. However, the intrinsic excitation dynamics of Chl derivatives remain unclear. Here, we show sub-nanosecond pump–probe time-resolved absorption spectroscopy of Chl derivatives both in solution and solid film states. We observe the formation of triplet-excited states of Chl derivatives both in deoxygenated solutions and in film samples by adding all-trans-β-carotene as a triplet scavenger. In addition, radical species of the Chl derivatives in solution were identified by adding hydroquinone as a cation radical scavenger and/or anion radical donor. These radical species (either cations or anions) can become carriers in Chl-derivative-based solar cells. Remarkably, the introduction of hydroquinone to the film samples enhanced the carrier lifetimes and the power conversion efficiency of Chl-based solar cells by 20% (from pristine 1.29% to 1.55%). This enhancement is due to a charge recombination process of Chl-A + /Chl-D – , which is based on the natural Z-scheme process of photosynthesis. Chlorophyll derivatives can be applied in bio-solar cells, but their excited-state dynamics are not fully understood in this context. Here pump–probe time-resolved absorption spectroscopy measurements of chlorophyll derivatives reveal enhanced lifetimes of radical species in the presence of hydroquinone.