Photon recycling and efficiency limit of a silicon solar cell with Lambertian surfaces

Aliabadi Farahani, Faezeh (2023) Photon recycling and efficiency limit of a silicon solar cell with Lambertian surfaces. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis introduces an idealized silicon solar cell with Lambertian front and back surfaces. We assume that the reflection coefficient of the back surface is 1. When a photon enters the solar cell, it gets refracted by a randomly corrugated front surface and subsequently undergoes random reflections by back and front surfaces until it either gets absorbed or escapes the material with the probability that depends on the material’s refractive index. After each reflection event, the angle of photon propagation relative to the normal is randomized with Lambertian distribution. This thesis is focused on the photons produced in the radiative recombination events inside the cell. An exact analytical expression for the probability of photon reabsorption and recycling in an idealized solar cell with two Lambertian surfaces is derived. The existing approximations are found to agree with the exact formula to within 5 %. The most accurate approximation turned out to be the simplest one that sets the reabsorption probability to the weak-absorption limit of the cell absorptance. The maximal photoconversion efficiency of a silicon solar cell is evaluated to be 29.5% at the base thickness of 98 μm.

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