LAUSR

Abstract An analytical model based on charge neutrality principle and energy band diagram analysis is investigated to model a new structure of silicon heterojunction solar cell, which encompasses both homo and heterojunctions. In the analysed structure, a thin (p+)c-Si and a thin (n+)c-Si layers are used at front and back surfaces of (n)c-Si substrate respectively. The purpose of incorporating these layers is to reduce the solar cell output parameters sensitivity to a-Si:H/c-Si interface defect densities, increase the open circuit voltage ( V o c ) and increase the fill factor ( F F ) . Since (n)c-Si silicon bulk becomes quasi neutral in the mentioned structure, charge neutrality equation can be separated as two independent equations for front and back surfaces. Solving charge neutrality equations, result in a-Si:H/c-Si interface potential, and subsequently charge concentration, electric field, surface recombination velocity, and open circuit voltage ( V o c ) calculation. Then, by adjusting doping concentration of the two additional layers, their effect on surface potential and energy band bending is studied. It is observed that when doping concentration of (p+)c-Si layer is increased from 1 × 10 18 c m − 3 to 5 × 10 19 c m − 3 , the V o c drops by 15 m V , and F F increases by 2.5 % , while V o c and F F sensitivity to interface defects density is improved considerably. On the other hand, by (n+)c-Si layer insertion at back surface, in addition to decreasing sensitivity to interface defect densities in comparison to conventional SHJ silicon solar cell, V o c and F F are increased due to combination of high conductivity and enhancement of field effect passivation at back surface of solar cell. Moreover, when doping concentration of (n+)c-Si layer increases from 1 × 10 18 c m − 3 to 5 × 10 19 c m − 3 V o c and F F increases from 680 mV and 71% to 740 mV and 82% respectively.