Candidate
Christopher J Baldus-Jeursen
Title
Heterojunction Photovoltaic Devices With Rapid Thermally Annealed Crystalline Thin Films
Supervisor
Siva Sivoththaman
Abstract
Rapid thermal annealing is a low thermal budget high throughput method of creating crystalline silicon films from highly doped amorphous precursors deposited on silicon wafers. This thesis investigates a variety of thermal profiles to crystallize thin layers of amorphous silicon both on bare crystalline substrates and substrates coated with thin silicon nitride interface passivation layers. Techniques used to analyse film crystallinity include ultraviolet reflectance, Raman, XRD, ellipsometry, and Hall Effect. Electrical characterization of solar cell devices is explored to define the optimal annealing profiles and determine which recombination mechanisms limit device performance. Even without high efficiency features such as back surface field or texturing, solar cell efficiencies up to 15.1% were achieved. Simulation of heterojunction devices is performed using AFORS-HET software with an emphasis on the effect of interface defects. Simulations examine electrical and optical qualities of thin crystalline and amorphous emitter layers, interface defect electroluminescence, and capacitance spectroscopy with variation of ac frequency and temperature.