Simulation of a Silicon Heterojunction Solar Cell with a Gradient Doping Emitter Layer

A silicon heterojunction solar cell structure consisting of a gradient doping emitter layer, which possesses a potential to obtain high power conversion efficiency, is explored by the numerical simulation tool automat for simulation of heterostructures. We have demonstrated that the gradient doping solar cell has a higher open-circuit voltage than a uniform doping solar cell, due to the introduction of an additional electric field, which can achieve a better conversion efficiency, whereas their thickness and defect state distribution are identical. A high conversion efficiency of 29.5% is achieved by using a gradient doping for the n-type emitter layer with the same reference as the uniform doping. In addition, through the investigation of the effect of gradient doping, we find that the field-effect passivation can appropriately explain the interesting behaviors that the recombination rate is less sensitive to the defect density state, and that the open-circuit voltage is enhanced when increasing the doping gradient in the n-a-Si emitter layer.