Preparation and characterization of mirrocrystalline and epitactially grown emitter layers for silicon solar cells

摘要

We have deposited thin B- and P-doped Si layers by electron cyclotron resonance CVD on c-Si (4 #OMEGA#cm, CZ) and on quartz glass substrates at T=325 deg C. Films grown on quartz glass are of microcrystalline nature with crystalline volume fractions of about 70 percent and a resistivity ranging from 0.01 - 10 (#OMEGA#cm)~(-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 P- doping. 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 11percent for cells without ARC. The result are compared to cells with diffused emitters, otherwise prepared with the same technological steps.