Preparation and Characterization of Microcrystalline and Epitactially Grown Emitter Layers for Silicon Solar Cells

Abstract

AbstractWe have deposited thin B- and P-doped Si layers by electron cyclotron resonance CVD on c- Si (4 Ωcm, CZ) and on quartz glass substrates at T=325°C. Films grown on quartz glass are of microcrystalline nature with crystalline volume fractions of about 70 % and a resistivity ranging from 0.01 - 10 (Ωcm)−1 depending on doping concentration. The doping efficiency is close to unity with the carrier mobility being independent of doping concentration for both B- and Pdoping. Films grown on c-Si, on the other hand, exhibit perfect homoepitaxial morphology when the gas phase doping concentration exceeds 1000 ppm and 5000 ppm for P- and B-doping, respectively. The quality of the films is tested by preparing thin film emitter solar cells. We find efficiencies above 11 % for cells without ARC. The result are compared to cells with diffused emitters, otherwise prepared with the same technological steps.