Photovoltaic investigation of minority carrier lifetime in the heavily-doped emitter layer of silicon junction solar cell

Abstract

The minority carrier lifetime in a phosphorous-diffused layer of a conventional N+/P silicon photocell has been investigated experimentally. The photovoltages have been measured as a function of photon flux density from low to medium illumination levels. From the quasi-Fermi level analysis of Gray-Kao-Schroder, we have determined the carrier recombination lifetime as a function of the photogeneration rate 〈G〉 in the heavily-doped N+ layer. When the band gap narrowing effect is taken into consideration, the recombination processes can be described by (i) a ’’positive-field controlled’’ Shockley-Reed-Hall recombination at low photo injection level, (ii) a ’’positive-field influenced’’ Auger recombination at the medium injection level, and (iii) a ’’negative-field controlled’’ Auger recombination at the high injection level. Under a very high photoexcitation condition, the magnitude of the saturated open circuit voltage of the cell is limited by the recombination lifetime at the surface contact region.