Energies, Vol. 18, Pages 4751: Tunable Dye-Sensitized Solar Cells via Co-Sensitization and Energy Transfer from Spiropyran Derivatives to YD2

Energies, Vol. 18, Pages 4751: Tunable Dye-Sensitized Solar Cells via Co-Sensitization and Energy Transfer from Spiropyran Derivatives to YD2

Energies doi: 10.3390/en18174751

Authors:
Keitaro Ono
Ryuhei Ejima
Michihiro Hara

We fabricated dye-sensitized solar cells (DSSCs) co-sensitized with the organic dye YD2 and a spiropyran derivative (SPNO2), a photochromic molecule capable of reversible isomerization under light irradiation. Upon UV exposure, SPNO2 converts from its closed spiropyran (SP) form to the open photomerocyanine (PMC) form, which absorbs visible light and changes the optical properties of the photoelectrode. Spectroscopic analysis showed an 18% decrease in transmittance at 540 nm after UV irradiation and a 10% increase following visible light exposure. These changes were accompanied by a 0.5% increase in power conversion efficiency (η) after 5 min of UV irradiation, and a 0.83% decrease after 10 min of visible light. Although direct electron injection from PMC into TiO2 appears inefficient, the enhanced performance is attributed to Förster resonance energy transfer (FRET) from PMC to YD2. This photoresponsive behavior highlights a co-sensitization strategy that combines dynamic optical control and efficient energy transfer. Our findings demonstrate a promising approach to designing smart DSSCs with externally tunable photovoltaic properties using photochromic sensitizers.