Preparation of F-passivated ZnO for quantum dot photovoltaics

For photovoltaic power generation, pn junction is the core unit. The electric field in the junction can separate and transport electron and hole to negative and positive electrode, respectively. Once the pn junction is connected with a load and exposed to a light ray, it can convert photon power into electrical power and deliver this power to the load. This photovoltaic application has long been used for the power supply of satellite and space vehicle, and also as the power supply of renewable green energy for human.

As the star materials, Si, GaAs, and perovskite has been widely applied for solar power harvesting. However, the absorption cutoff wavelength of these materials is below 1100 nm, which limits their photovoltaic applications in infrared photon power. Hence, it is urgent to explore new materials for photovoltaics. Among various materials, PbSe colloidal quantum dots (CQDs) are promising candidates for photovoltaics because its photoactive range can cover the whole solar spectrum. Thanks to the rapid advances of metal halide ligands and solution phase ligand exchange process, the efficiency of PbSe CQD solar cells approaches to 11.6%. In view of these developments, further improvement for device performance can focus on the optimization of electron transport layer (ETL) and hole transport layer (HTL).

Dr. Jungang He at Wuhan Institute of Technology (WIT) and Prof. Kanghua Li at Huazhong University of Science and Technology (HUST), China, are interested in the improvement of ETL. They have already reported a record efficiency of PbSe CQD solar cells. In order to further improve the performance with little change the device architecture, they focus on the optimization of F-passivated ZnO. F ions are chosen for defect passivation of ZnO because the radius of F ions is similar to that of oxygen ions. Hence, the trap density of ZnO can be decreased and the device performance can be improved. The work entitled “Fluoride passivation of ZnO electron transport layers for efficient PbSe colloidal quantum dot photovoltaics” was published on Frontiers of Optoelectronics (published on Oct. 27, 2023).