From leds to solar cells: opto-electrical simulation and photon recycling

This thesis explores the theory and practical application of simulation methods in optoelectronic devices. Computational methods have been applied to model the performance of recently introduced optoelectronic sensors and perovskite solar cells. It begins by reviewing the importance of optoelectronic devices and numerical methods, providing a general foundation. Common optical simulation methods in the semiconductor field are discussed, such as the full solution of Maxwell’s equations, Ray tracing, and TMM. Detail balance approach and drift-diffusion methods are also discussed, as they are widely used in solar cell research works. The second chapter employs ray tracing and the full solution of Maxwell’s equations to analyze the performance of an optical sensory system comprising a pair of LEDs and a photo-detector. The entire sensory system is placed on a single commercial GaN LED substrate, offering a simple fabrication process and lower power consumption. The sensor is designed to monitor changes in the optical constants of the analyte, which is deposited on top of the GaN substrate. Ray tracing and the full solution of Maxwell’s equations have been used to model the interaction of the emitted light with the analyte. We utilized wave optics results to build a modified version of ray tracing to consider evanescent waves in the simulations. In addition, we also studied how non-uniformity in optical absorption of the analyte affects the performance of the sensor. In the third chapter, we turn the focus to solar cells. The TMM and drift-diffusion model are used to model the performance of perovskite solar cells using TiberCAD. Initially, a single perovskite cell has been modeled and results compared with experimental results. Comparisons indicate that TiberCAD is reliable and accurate software for simulation of the solar cell. The chapter continues with simulations of perovskite/silicon tandem solar cells and the application of perovskite solar cells for underwater operation. The iterative process of emission and absorption of photons within optoelectronic devices is termed photon recycling. Several methods have been developed by researchers to investigate this phenomenon in solar cells. However, in Chapter fourth, we present a novel self-consistent model that combines TMM and driftdiffusion to analyze the photon recycling effect in solar cells. This model has been implemented in TiberCAD. We have observed a good agreement between our simulation results and previous research works. Furthermore, we explore the effects of SRH recombination and active layer thickness on the photon recycling effect. Our findings suggest that the photon recycling effect is more pronounced in devices operating close to the radiative limit. Additionally, we found that the device geometry and parasitic absorption are additional parameters that affect the photon recycling effect. The thesis concludes with a summary of our findings and suggestions for future research directions.