Low cost thin film silicon solar cells on upgraded metallurgical (UMG) silicon substrates prepared by liquid phase epitaxy (LPE)

摘要

Liquid Phase Epitaxy (LPE) was used to grow high quality thin p-type silicon films with a doping level of 5×10{sup}16 cm{sup}-3 on upgraded metallurgical (UMG) Si substrates. A melt back step prior to the growing removed the oxide, smoothed out the surface and circumvented the addition of electronic grade Si to the solution. With a steady state method the growth rates were < 0.5μm/min. Higher rates were achieved by ramping down the temperature. The crystal structure and the electronic quality of the Si film strongly depended on the growth rate. The pn-junction was realized by a low cost P diffusion. Hydrogen passivation was quite effective and resulted in an increase in the efficiency of up to 60% relative. Contact formation was performed by both screenprinting and evaporation of Ti/Pd/Ag and Al respectively. The solar cells were analysed by I/V measurements, LBIC, SEM and spectral response data. Cells with evaporated contacts reached fill factors up to 74.1%, a V{sub}(OC) of 551 mV and a I{sub}(SC) of 14.7 mA/cm{sup}2. Therefore an efficiency of 6.0% could be achieved without antireflection coating (ARC) (η = 8.3% with ARC). Cells based completely on a low cost process (emitter diffusion and contacts) resulted in efficiencies of 6.6% without and 9.0% with ARC.