High-Concentration Photovoltaics—Effect of Inhomogeneous Spectral Irradiation

At high solar concentration, subtle optical and electrical effects in combination can have a substantial impact on photovoltaic power (PV) generation. We have identified such an effect through its clear signature: a “ripple” in the output current with respect to the pointing angle of the concentrated PV (CPV) system to sun direction. At small angular misalignment, this effect can lower cell current by as much as 15% at 1600x concentration in full sun. At medium concentration between 500 and 1000x, while not as clearly visible in single cells, the effect also reduces output by a smaller amount. The disappearance of the “ripple” signature at low concentrations below 300x indicates that the effect is not a linear effect, such as a light loss. We attribute the pronounced angular sensitivity of power output at high concentrations to a combination of inhomogeneous spectral irradiation incident on the multijunction solar cell and of the impact of the finite lateral resistance of the cell.