Chemical Bath Deposition of Stoichiometric CdSe Quantum Dots for Efficient Quantum-Dot-Sensitized Solar Cell Application

Cadmium selenide (CdSe) quantum dots (QDs) have been prepared by suppressing the formation of an amorphous selenium oxide (SeO2) layer on the surface of CdSe QDs. The precursor ratio for the chemical bath deposition was optimized to minimize the SeO2 layer growth and develop high-efficiency CdSe QDs for quantum-dot-sensitized solar cell (QDSSC) applications. The morphologies and optical and electrical properties of the CdSe QDs were investigated, and the growth mechanism was also proposed for the CdSe and SeO2 layer formation. Furthermore, electrochemical impedance spectroscopy results indicated that the SeO2 layer reduced the recombination resistance of photogenerated electron-hole pairs, thus degrading the cell efficiency. Therefore, a QDSSC based on an optimized CdSe/CdS/ZnO nanowire photoanode, polysulfide electrolyte, and Au counter electrode can enhance the power conversion efficiency to 4.8% under AM 1.5 G one-sun illumination.