Photovoltaic Effect in Silicon Treated by Compression Plasma Flows

Photovoltaic effect on single-crystalline silicon treated by compression plasma flows is studied. A number of samples (1 1 cm) of single-crystalline silicon with n- and p-types of conductivity and different dopant concentrations (p-type silicon doped by B: 0.3, 4.5, 10, 12 Ω cm; n-type silicon doped by P: 0.5, 4.5, 20 Ω cm) were treated by nitrogen, hydrogen and helium compression plasma flows with energy density 5-12 J/cm2. Open-circuit voltage (AM1.5 spectrum of solar irradiation) dependence on plasma-forming gas, type of conductivity and dopant concentration was studied. It was established that photovoltaic effect takes place only in p-type silicon. The effect is maximal for boron concentration 4.5 Ω cm. Nitrogen plasma treatment causes appearance of photovoltaic effect for all types of p-silicon. At the same time after helium and hydrogen plasma treatment the effect is observable only for 4.5, 10 and 12 Ω cm samples and is absent for 0.3 Ω cm silicon. Thermo-EMF sign measurements show that the present effect is connected with appearance of new additional donors under plasma action in pre-surface layer.Possible reasons of donor appearance are silicon doping by nitrogen and appearance of thermo-donors. Compression plasma flows can be considered as perspective cheap method of silicon treatment for silicon based solar cell technology.