Improving the efficiency of industrial samples of silicon solar elements

Abstract

Possibilities of increasing the efficiency by more than 20 % for silicon photoelectric converters made in China have been investigated. It has been established by the method of computer simulation that the life-times of nonequilibrium charge carriers, which are 520 μs, realized in such photoelectric converters, do not limit the possibility of increasing their efficiency by more than 20 %. It is shown that an increase in the photocurrent density to 43.1 mA/cm2 leads to an increase in efficiency to 20.1 %, and a decrease in the diode saturation current density to 3.1∙10-14 A/cm2 leads to an increase in efficiency to 20.4 %. Simultaneous change of these diode characteristics leads to an increase in efficiency to 23.1 %. The paper proposes physical and technological approaches to increase the photocurrent density and reduce the diode saturation current density in ready-made photovoltaic converters. The study of the influence of operating temperature on the efficiency of crystalline silicon photoelectric converters is carried out in the article. It is shown that with increasing operating temperature the relative decrease in the efficiency of single-crystal devices is –0.7 relative %/C, which is significantly higher than in the instrument structures of European production and due to non-traditional decrease in short-circuit current density. Mathematical modeling of the influence of light-emitting diode characteristics on the efficiency of crystalline silicon solar cells showed that the decrease in the efficiency of instrument structures with increasing operating temperature is due not only to an increase in diode saturation current density from 10-13 A to 3·10-13 A, which is 300 %, but also by reducing the shunt resistance from 2.5 kOhm to 1.5 kOhm. A study of the effect of operating temperature on the diode saturation current showed that the height of the potential barrier in the studied silicon photovoltaic converters is 0.87 eV, due to the insufficient level of doping of the base material. The limited height of the potential barrier leads to an unconventional decrease in the shunt resistance with increasing operating temperature.