The modeling group deals with the development and application of detailed mathematical models to describe the physics relevant to the operation of (thin-film) solar cells. Using simulations in combination with experiments allows for a detailed analysis of the physical processes involved in device operation, and thus helps in understanding, characterization and optimization of materials and devices.
We apply and develop both optical and electrical models. Thin film silicon solar cells commonly apply textured interfaces and highly reflective back contacts to enhance light absorption. The resulting optical properties of these devices are rather complex. For modeling of such complex structures we use various software tools that either numerically solve Maxwell's equations or utilize simplified models based on ray tracing.
The electrical properties of thin-film silicon devices are modeled using the classical semiconductor equations. Thin-films of amorphous and microcrystalline silicon are disordered semiconductors, which exhibit many structural defects that strongly influence the electrical properties of the material. Therefore, in addition to the semiconductor equations, we use models describing the electronic properties of these disordered materials. The resulting electrical model is readily combined with the discussed optical models.
Third generation solar cells are based on quantum effects and therefore these new types of solar cells need a quantum theory of photovoltaic processes in nanostructures. To this end we develop models for solar cells based on quantum effects, which consistently describe optical properties, optical absorption, quantum transport (tunneling, confinement, and coherence), scattering effects, and current injection.