Solar Paint from TiO₂ Particles Supported Quantum Dots for Photoanodes in Quantum Dot-Sensitized Solar Cells

The preparation of quantum dot (QD)-sensitized photoanodes, especially the deposition of QDs on TiO₂ matrix, is usually a time-extensive and performance-determinant step in the construction of QD-sensitized solar cells (QDSCs). Herein, a transformative approach for immobilizing QD on the TiO₂ matrix was developed by simply mixing the as-prepared oil-soluble QDs with TiO₂ P25 particles suspension for a period as short as half a minute. The solar paint was prepared by adding the TiO₂/QD composite in a binder solution under ultrasonication. The QD-sensitized photoanodes were then obtained by simply brushing the solar paint on a fluorine-doped tin oxide substrate followed by a low-temperature annealing at ambient atmosphere. Sandwich-structured complete QDSCs were assembled with the use of Cu₂S/brass as counter electrode and polysulfide redox couple as an electrolyte. The photovoltaic performance of the resulting Zn-Cu-In-Se (ZCISe) QDSCs was evaluated after primary optimization of the QD/TiO₂ ratio as well as the thicknesses of photoanode films. In this proof of concept with a simple solar paint approach for photoanode films, an average power conversion efficiency of 4.13% (J _sc = 11.11 mA/cm², V _oc = 0.590 V, fill factor = 0.631) was obtained under standard irradiation condition. This facile solar paint approach offers a simple and convenient approach for QD-sensitized photoanodes in the construction of QDSCs.