Reduced temperature dependence of high-concentration photovoltaic solar cell open-circuit voltage (Voc) at high concentration levels

Thermal management has been an important issue for both one-Sun flat-plate, and concentration PV power system applications. It is well known that system output power, or efficiency, decreases with the increasing temperature of the solar cell incorporated within the system mainly due to a decrease in open-circuit voltage (Voc) as a function of increasing temperature. This paper reports the measurement results of temperature sensitivity for Voc of AMONIX´s high-concentration photovoltaic (HCPV) cells at various temperatures (25°C-65°C), and various concentration levels (one-Sun up to 500 Suns under AM 1.5) and compares against typical one-Sun flat-plate manufacturer´s data. Even after taking into account the negative temperature dependence of the fill factor, the study shows that output power in concentration systems is less affected by temperature variations compared to one-Sun flat-plate designs. The overall effect of this reduced temperature sensitivity for Voc of the HCPV cell on the power output at operating temperature is analyzed and compared against typical single and poly-crystalline silicon, front-junction, one-Sun, flat-plate manufacturer´s data. Experimental and analytical results show that typical flat-plate PV power systems have a -0.4%/°C (4000 PPM) decrease in power versus -0.25%/°C (2500 PPM) for high-concentration systems