Open circuit voltage of MIS Schottky diode solar cells

Abstract

The efficiency of p-n junction solar cells is limited by the high sheet resistivity of the semiconductor. Schottky barrier solar cells, while not limited by this resistivity problem, suffer from low output voltage. The output voltage of Schottky barrier cells is proportional to the logarithm of the ratio of the light current to the dark current. The dark current is, in turn, proportional to the exponential of the barrier height. Thus, high barrier height means high open circuit voltage. Barrier height can be controlled through the surface states and through the use of thin insulating layers between the metal gate and the semiconductor. In this paper, the results of theoretical and experimental studies on barrier height control are presented. Data on the effect of barrier height on open circuit voltage are presented. Particular attention is paid to the role of oxide thickness and minority carriers in the semiconductor space charge region in determining barrier height. It is shown both theoretically and experimentally that MIS solar cells can approach the performance of a commerical p-n junction solar cell.