Photovoltaic Characteristics Of Gradient Doped Homo-heterojunction Solar Cells

With the continuous improvement of industrialization,the uncontrolled exploitation and use of fossil energy make the world face the threat of energy shortage and environmental pollution.So far,a large number of new energy are emerging and applied in all aspects of production and life.Among many new energy sources,solar energy has the advantages of wide coverage,clean,safe,green and pollution-free.The solar cell which uses photovoltaic effect to convert solar energy into electric energy has become the top priority of the research.There are many kinds of solar cells,and the preparation technology has been gradually improved.Up to now,the research of HH cells mainly focuses on the influence of various factors on the output characteristics when the back field and emitter are uniformly doped.However,it has not been reported when the emitter and back field are gradient doped.In this work,the numerical simulation software AFORS-HET is used to optimize the doping concentration of emitter and back field.In addition,the emitter and back field of HH battery are divided into five equal parts,and the doping concentration decreases or increases linearly from top to bottom,so as to achieve the effect of gradient doping of HH cells.On the premise of the same total doping concentration,the performance of HH cells with uniform doping is compared in the following aspects:（i）emitter doping concentration（N_e）,（ii）The thickness of the emitter,（ⅲ）the doping concentration of the back field,（iv）Defect density at the former heterointerface,（v）Suspended bond defect density of states in the emitter(N_tr),（ⅵ）the work function of the transparent conductive oxide layer.The results are shown as follows:（1）The gradient doping of emitter can improve the output performance of HH solar cells.This is mainly because when the emitter is gradient doped,the carrier distribution in the cell is uneven,resulting in an additional electric field.The direction of the additional electric field is consistent with the built-in electric field,which enhances the conversion efficiency of HH solar cells.（2）The back field gradient doping will not improve the photovoltaic characteristics of HH cells.（3）The stability of HH cells doped with emitter gradient is higher.