Temperature coefficients of concentrator solar cells up to ultra-high irradiance

A flash-like, real-sun optical system has been used to experimentally measure the effect of irradiance (from 11 up to 8,600 suns) on the temperature coefficients of the key performance parameters of multijunction concentrator solar cells. Particular attention is paid to the time scales and magnitudes of junction heating, hence the degree to which the cell can be deemed isothermal, with implications for corresponding measurements from solar simulators with pulsed artificial light, and for the performance evaluation of concentrator photovoltaics. The theoretical bound for the magnitude of the temperature coefficient of V_oc (as function of irradiance) has also been calculated for current commercial triple-junction structures.