Surface recombination and internal currents in a vertical-junction solar cell

Expressions for short-circuit current and open-circuit voltage for a vertical-junction solar cell are derived using two-dimensional analysis. The analysis shows that the effects of surface recombination in vertical-junction and conventional solar cells are comparable for small values of W (the width of the p layer) and S n (the surface recombination velocity). As the values of S n and/or W increase, the effect of surface recombination increases more rapidly in the vertical-junction cell. It is found that in the open-circuit configuration circulatory drift currents flow inside the solar cell and a part of the energy is wasted inside the cell itself. The voltage everywhere across the junction is reduced to a value equal to that at the bottom of the cell. The use of a totally reflecting bottom mirror to minimize the internal currents and to improve the open-circuit voltage is suggested.