Charge-carrier recombination is the central process that realizes energy conversion in optoelectronic materials and plays a decisive role in determining the device efficiency. The recombination coefficients can be experimentally measured by using the carrier rate equation to fit the decay of, for instance, photoconductivity with different excitation pulse fluences. However, numerical fits of multiple parameters may involve significant uncertainties. Also, measurements of the coefficients do not allow direct and intuitive interpretation of the microscopic recombination mechanisms.
First-principles approaches may overcome this limitation and become particularly useful in this context. They allow not only rigorous computation of the recombination rates, but also intuitive interpretation of the microscopic recombination mechanisms from the electronic structure point of view. In recent years, we have developed a full set of first-principles approaches to compute the coefficients of different types of recombination processes, including first-order defect-assisted Shockley-Read-Hall recombination, second-order radiative recombination, as well as third-order Auger recombination (see Fig. 1). These methods were applied to technologically very important optoelectronic materials such as halide perovskites, which have yielded critical insights into the loss mechanisms and potential strategies for improved materials design.
Further details will be presented at the NUSOD-22 conference.
Fig. 1 Schematic for charge-carrier recombination processes of different orders.
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