Nd sub(2)(S, Se, Te) sub(3) Colloidal Quantum Dots: Synthesis, Energy Level Alignment, Charge Transfer Dynamics, and Their Applications to Solar Cells

Novel and less toxic quantum dot (QD) semiconductors are desired for developing environmentally benign colloidal quantum dot solar cells. Here, the synthesis of novel lead/cadmium-free neodymium chalcogenide Nd sub(2)(S, Se, Te) sub(3) QDs via solution-processed method is reported for the first time. The results show that small-bandgap semiconductor QDs with a narrow size distribution ranging from 2 to 8 nm can be produced, and the wide absorption band can be achieved by the redshift owing to the size quantization effect by controlling the initial loading of chalcogenide precursors. By analyzing the band structure of QDs and the energy level alignment between QDs and TiO sub(2), the influence of energy offset between the conduction band edges of QDs and TiO sub(2) on the charge transfer dynamics and photovoltaic performance of QD solar cells (QDSCs) is investigated. It is revealed that among the three types of QDs studied, Nd sub(2)Se sub(3) QDSCs with the smallest energy offset exhibit the best performances and a decent power conversion efficiency of 3.19% is achieved. This work clearly demonstrates the promising potentials of novel rare earth chalcogenide quantum dots in photovoltaic applications. Lead/cadmium-free and optimized neodymium chalcogenide quantum dots (QDs) have been synthesized by varying the ratio of neodymium to chalcogenide and their promising applications to solar cells have been demonstrated in terms of optical properties, energy level alignment, and charge transfer dynamics, etc. Nd sub(2)Se sub(3) QDs exhibit a faster charge transfer rate and a conversion efficiency of 3.19% has been achieved.