Cell efficiency dependence on solar incidence angle

Triple junction photovoltaic cells used in concentrating PV systems normally have grid lines on the top surface that act as one of the two contacts of the cell. The effect of these grid lines on the optical coupling between the secondary optic and the PV material is studied and an analytic model is developed that describes the cell performance as light enters in an off-axis orientation. With a secondary optic attached to the multijunction cell, the angle of incidence on the cell will have a wide range from 0-90 degrees from normal. This paper explores how the efficiency of the cell changes as the light angle of incidence changes by using experimental data and estimation of measurement errors to develop a model to predict cell performance at various angles of light incidence. Light incident parallel to the grid lines is compared to light incident perpendicular to the grid lines.