Drift-diffusion simulations have proven very useful to understand the properties of novel devices such as perovskite solar cells. In order to make such simulations widely accessible and transparent, we have developed an open-software simulation suite called SIMsalabim. SIMsalabim incorporates hysteresis, ions, and tracking of the open-circuit voltage, as well as the ability to include scripting for different measurement techniques such as CELIV, TPC, TPV, and impedance spectroscopy. This makes it possible to fit simulation results to experimental data, including global fits of multiple experiments. To improve user experience and encourage its use by researchers in the field of photovoltaics, we have recently developed a web-version of SIMsalabim that runs in a web-browser [1]. In this talk, a few examples of the applicationof drift-diffusion modelling will be discussed.

Space-charge-limited current (SCLC) measurements have been widely used to study the charge carrier mobility and trap density. However, their applicability to metal halide perovskites is not straightforward, due to the mixed ionic and electronic nature of these materials. Here, we discuss the pitfalls of SCLC for perovskites, and especially the effect of mobile ions. We show, using drift-diffusion simulations, that the ions strongly affect the measurement and that the usual analysis and interpretation of SCLC need to be refined. We highlight that the trap density and mobility cannot be directly quantified using classical methods. We discuss the advantages of pulsed SCLC for obtaining reliable data with minimal influence of the ionic motion. We then show that fitting the pulsed SCLC with DD modeling is a reliable method for extracting mobility, trap, and ion densities simultaneously.

Wide-bandgap perovskite solar cells are plagued by relatively low open-circuit voltages. Here, a number of design rules to increase the open-circuit voltage of wide-bandgap perovskite solar cells are introduced. The combined effects of interface traps, ions, band alignment, and transport properties are introduced to identify the critical parameters for improving the open-circuit voltage. We show that the alignment of energy levels is only part of the story; the effective densities of states are of equal importance. The results pave the way to achieving high open-circuit voltages, despite a significant density of interface defects.

[1] simsalabim-online.com