| Summary: | <p>This thesis studies the production and performance of p-type inversion layer (IL) Si solar cells. IL cells use an electric field to induce an inversion layer and create a <i>pn</i> junction. Compared with the mainstream diffused <i>pn</i> junctions, the advantages of field-induced junctions include lower fabrication costs and less carrier recombination. IL cells have been studied since the 1970s. In previous work, intrinsic charge in dielectric materials has been used to induce the inversion layer. However, the charge density was not high enough to induce a sufficiently conductive junction emitter (n-type surface layer). In this thesis, a field and temperature-assisted ion migration method was used to incorporate a controllable amount of positive ionic charge into dielectric thin films and fully exploit IL cells.</p>
<p>The ion migration method was first used to induce an electron accumulation layer on n-type substrates. The lowest accumulation layer sheet resistance (Rsh) obtained is 950 W/sq, which is the lowest reported in the literature. A model was developed in Sentaurus TCAD to study the formation and properties of field-induced layers. The simulation results suggested that the Rsh is determined by charge density, band-tail interface state density, and illumination. With optimised charge density and interface parameters, the lowest IL Rsh that can be achieved in the dark is 1.1 kW/sq. Although such Rsh is ~7 times higher than that of typical n-type phosphorous-diffused emitters (150 W/sq), the cell performance evaluated by device simulations is not limited by the high Rsh. The simulation model comprises a field-induced emitter and a PERC-like structure at the rear. The best simulated IL cell shows an efficiency of 24.8%, comparable to the best predicted for PERC. This indicates that field-induced emitters can perform as well as P-diffused emitters.</p>
<p>Proof-of-concept IL cells were fabricated via laser doping, annealing, ion migration, and light-assisted electroplating. The formation and uniformity of the field-induced emitter were confirmed by taking a photocurrent map of the IL cell. The champion cell presents an efficiency of 10.8%, demonstrating that IL cells can be fabricated using the ion migration method. Although the efficiency is low, simulation results suggest that an efficiency of as high as 24.8% can be achieved with optimised processing. With low fabrication costs and high potential cell efficiencies, field-induced emitters can become competitive alternatives to P-diffused emitters in commercial applications.</p>
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