Effect of Doping, Photodoping, and Bandgap Variation on the Performance of Perovskite Solar Cells

Most traditional semiconductor materials are based on the control of doping densities to create junctions and thereby functional and efficient electronic and optoelectronic devices. The technology development for halide perovskites had initially only rarely made use of the concept of electronic doping of the perovskite layer and instead employed a variety of different contact materials to create functionality. Only recently, intentional or unintentional doping of the perovskite layer is more frequently invoked as an important factor explaining differences in photovoltaic or optoelectronic performance in certain devices. Here, numerical simulations are used to study the influence of doping and photodoping on photoluminescence quantum yield and other device relevant metrics. It is found that doping can improve the photoluminescence quantum yield by making radiative recombination faster. This effect can benefit, or harm, photovoltaic performance given that the improvement of photoluminescence quantum efficiency and open-circuit voltage is accompanied by a reduction of the diffusion length. This reduction will eventually lead to inefficient carrier collection at high doping densities. The photovoltaic performance may improve at an optimum doping density which depends on a range of factors such as the mobilities of the different layers and the ratio of the charge carrier capture cross sections.