1. IMPROVED, LOW-COST SILICON SOLAR CELL EMITTERS PRODUCED VIA LIQUID PHASE EPITAXY DOPING
Name: Ernesto Magana
Grad Year: 2020
To make silicon solar cells more accessible, we investigate methods for improving their efficiency and reducing their overall cost of production. Currently, silicon solar cell performance is largely limited by recombination in the heavily n-doped, top-most layer ? commonly referred to as the emitter. Typical fabrication of n-type emitters involves a POCl3 diffusion process, which requires high temperatures (greater than 800°C) and leads to large equipment costs. Furthermore, in POCl3-diffused emitters, the dopant concentration and depth profile, both critical to determining electronic performance, are dependent on solid-state diffusion kinetics. Herein, an innovative method for emitter formation is proposed using liquid phase epitaxy (LPE) to produce finely-tuned emitters, aimed at increasing solar cell performance and reducing their overall production costs. Liquid phase epitaxy has been studied for many years as a method to grow silicon at relatively low temperatures. LPE allows for doping profiles that would otherwise be impossible to produce using a standard diffusion process, as the peak dopant concentration, final emitter width, and process duration are independent of each other in contrast to solid-state processes. Simulations are used to compare the theoretical performance of LPE emitters against the state-of-the-art. Preliminary simulations indicate that using phosphorus as a dopant, an emitter produced by doping via LPE would result in an emitter saturation current density lower than that of most conventional diffused emitters (< 50 fA/cm^2).
Industry Application Area(s)
Energy/Clean technology | Materials | Semiconductor