Key factors limiting the open circuit voltage of n+pp + indium phosphide solar cells

The problem of the presently obtained best open-circuit voltage (V _oc) values of n⁺pp⁺ InP solar cells being considerably smaller than those predicted by basic theory is theoretically investigated. The values of some key parameters in the cells are obtained with a computer model by closely matching theoretical and measured curves for illuminated I-V, log I_sc-V_oc , and spectral response characteristics of a high-efficiency (17.9%) InP solar cell made by the Spire Corporation. An optimally designed InP solar cell with nearly the best efficiency that it is capable of providing in the n⁺pp⁺ shallow homojunction structure is described and modeled using these parameters. The performance parameters of the optimally designed solar cell are calculated, and it is shown that such a cell is capable of having an efficiency of 22.61% under 1 AM0 at 27°C (300 K). Using a baseline solar cell design which is a slightly modified and improved version of the Spire 6 cell, the key factors which limit the open-circuit voltage V _oc of such a solar cell are discussed