Patent ID: 8507787

Claim:
A solar cell comprising: a base layer; an emitter layer disposed on one side of the base layer; a first electrode in electrical communication with the base layer; and a second electrode in electrical communication with the emitter layer, wherein the base layer has a higher doping concentration with increasing distance from an interface between the base layer and the emitter layer, and the base layer has a doping concentration change slope that is decreased with increasing distance from the interface between the base layer and the emitter layer; wherein the doping concentration of the base layer is discontinuously changed, wherein the base layer has a distinguishable plurality of doping levels, and a thickness having the constant doping concentration of each doping level which is smaller than a diffusion length of a minority carrier, and wherein the base layer has a distinguishable plurality of doping levels, and a doping thickness in each doping level becomes thinner with increasing distance from the interface between the base layer and the emitter layer.