Temperature changes of I-V characteristics of photovoltaic cells as a consequence of the Fermi energy level shift

Abstract

Current voltage (I-V) characteristic of illuminated photovoltaic (PV) cell varies with temperature changes. The effect is explained according to the solid state theory. The higher the temperature, the lower the open-circuit voltage and the higher the short-circuit current. This behaviour is explained on the basis of band theory of the solid state physics. The increasing temperature causes a narrowing of the forbidden gap and a shift of the Fermi energy level toward the centre of the forbidden gap. Both these effects lead to a reduction of the potential barrier in the band diagram of the illuminated PN junction, and thus to a decrease of the photovoltaic voltage. In addition, narrowing of the forbidden gap causes higher generation of electron-hole pairs in the illuminated PN junction and short-circuit current increases.