Device model for intermediate band materials

For twenty years, intermediate band (IB) materials have been developed with the goal of making high-efficiency photovoltaics, with limiting efficiencies equivalent to triple-junction devices but with simpler and potentially less expensive device designs. IB devices have yet to produce any high efficiencies. Existing devices did not optimize such parameters as their layer thicknesses, because there was no device model that could treat all the IB-specific effects, e.g., charge transport within the IB and IB-filling-dependent absorptivity and photofilling. We present Simudo, a finite element optoelectronic device model that implements these effects, in addition to treating standard semiconductors. Simudo models charge transport and generation in the conduction, valence, and a number of intermediate bands. It solves the coupled Poisson/drift-diffusion equations in two dimensions, along with self-consistent optics for IB-filling-dependent absorption. We validate this new software by benchmarking it against Synopsys Sentaurus on a pn-diode test problem, and we show excellent agreement. Simudo enables optimization of devices as well as understanding of experimental results, bringing the well-established value of device modeling semiconductors to IB systems.