Upconverting TiO2 spheres with light scattering effect for enhanced quantum dot-sensitized solar cells

Abstract

Semiconductor quantum dots (QDs) for solar cells could only absorb solar light in the visible region. Upconverters could convert near-infrared (NIR) photons into visible light photons that could be used to generate photocurrent by the sensitizers. Consequently, it is reasonable to utilize upconverters in the quantum dotsensitized solar cells (QDSCs) in order to broaden the light utilization region. In this article, Yb3+/Er3+ co-doped TiO2 spheres were integrated into the photoanodes for QDSCs. The influence of photoanode configuration on the performance of the QDSCs has been scrutinized. The photoanode with the optimized composite film was employed to fabricate QDSC, yielding a conversion efficiency (η) of 3.53%. The QDSC with the composite film photoanode outperforms that with the pure TiO2 film photoanode. The amplified cell performance for the composite photoanodes could be attributed to the following two aspects: first, the upconversion process of the upconverter leads to indirect exploitation of NIR light. Second, the light scattering effect of the upconverterdoped TiO2 spheres enhances the absorption of visible light.