Temperature Dependent Charge Carrier Recombination in Organic Metal Halide Perovskite Photodetectors
Synthesis and Properties of Functional Materials
Final Report Abstract
The main goal of the project was to investigate the charge carrier dynamics of various perovskite compounds (FAxMA1−xPbI3), integrated as a light-absorbing layer in photodetectors. These perovskites have so far led to the highest efficiencies in thin-film solar cells and therefore promise excellent suitability for photodetectors and sensors. The focus here was on the relationship between the device temperature, the change in crystal structure associated with temperature changes, and the recombination processes of photo-generated charge carrier pairs. In contrast to the established semiconductors gallium arsenide and silicon that are often used in photodetectors, the phase transition temperatures of the novel perovskite semiconductors fall within the typical range of device operating temperature. Thus, temperature will have a significant impact on the functionality, characteristics and on the stability of perovskite photodetectors. In this project, layer architectures and coating processes developed at KIT for perovskite solar cells were modified according to the requirements of photodetectors. These new photodetectors were manufactured, optimized, and optoelectronically examined in the laboratories of Physics and the "SPECIFIC" laboratories in Swansea. Prof. Paul Meredith's department, a gloablly leading group in the analysis and simulation of photodetectors, has primarily worked on organic semiconductors until now. As planned, in this project high-performance perovskite photodetectors which exhibited exceptionally low dark currents of less than 100 picoamperes were successfully produced. However, in the temperature-dependent analysis these devices unexpectedly exhibited behavior where the photocurrents showed a negative temperature coefficient in the range of -20°C to 70°C. This phenomenon cannot be explained by a phase transition of the perovskite layer but only by a change in interfacial resistances between the active layer and charge transport layers, which has not been reported in the literature before.
