Tailored emitter, low-resistivity, ion-implanted silicon solar cells

Open-circuit voltages as high as 0.645 V (AM0, 25°C) have been obtained by a new process developed for low-resistivity silicon. The process utilizes high-dose phosphorus implantation followed by furnace annealing and simultaneous oxide growth. The effect of the thermally grown oxide is a reduction of surface recombination velocity; the oxide also acts as a moderately efficient antireflection (AR) coating. Boron-doped, float-zone silicon with resistivities from 0.1 to 1.0 Ω . cm has been processed according to this sequence; results show that the highest open-circuit voltage is obtained with 0.1 Ω . cm starting material. The effects of Auger recombination and bandgap narrowing caused by high doping concentrations in the n⁺-junction region have also been investigated by implanting phosphorus over a wide range of dose levels. The effects of emitter-phosphorus concentrations tailored to optimize electric fields in the emitter have also been investigated.