Amplification in Light Energy Conversion at Q-CdTe Sensitized TiO2 Photonic Crystal, Photoelectrochemical Stability in Se2– Electrolyte, and Size-Dependent Type II Q-CdTe/CdSe Formation

Abstract

This study investigates the ability of Se2– redox electrolyte to separate the photoholes and stabilize Q-CdTe quantum dot solar cell with a liquid junction. We examined the photophysical and photoelectrochemical behaviors of Q-CdTe in two sizes, green-emitting dots of 2.3–2.7 nm diameter and red-emitting dots of 4 nm diameter, in the presence of alkaline Se2– electrolyte prepared under inert atmosphere. Photoelectrochemical, absorbance, emission and emission quenching measurements revealed the presence of size dependence in Se2– surface binding to Q-CdTe, growth of type II Q-CdTe/CdSe, and stability in the photoelectrochemical cell. Emission quenching measurements show that Se2– scavenges the Q-CdTe photohole, with mechanisms that depended on size and quencher concentration. Binding of Se2– to green-emitting Q-CdTe occurred with a greater binding constant compared to the red-emitting dots, resulting in formation of type II Q-CdTe/CdSe at the smaller core indicated in red-shifted absorbance and emission sp...