Measuring the properties of colloidal PbS quantum dot thin films using differential photocarrier radiometry technology

Colloidal quantum dots have been widely applied in various optoelectronic devices such as solar cells, photodetectors, and light emitting diodes. The measurement of carrier dynamics not only allows the study of the passivation quality of quantum dot surfaces but also contributes to analyze the performance of related devices. In this study, by measuring and comparing the photocarrier radiometry signals of PbS quantum dot films on different substrates from the same batch, we investigated the carrier transport and trap properties in the material. First, based on the differences in surface recombination velocities of colloidal quantum dot films on different substrates, we established a theoretical model of differential photocarrier radiometry technique applicable to colloidal quantum dot films. We simulated and analyzed the effects of the carrier transport parameters, such as carrier lifetime, carrier hopping diffusivity, and surface recombination velocities, on the differential photocarrier radiometry signals. Finally, the photocarrier radiometry signals of PbS quantum dot films on K9 glass substrate and transparent indium tin oxide film coated glass substrate were experimentally measured, and the carrier transport parameters of the quantum dot films were also obtained through multiparameter fitting. The simulation and experimental results demonstrate that the differential photocarrier radiometry technique can be used for non-destructive measurement of the carrier transport and trap properties of colloidal quantum dot films without the adverse effects of instrument frequency response.