Quantum efficiency analysis of highly doped areas for selective emitter solar cells

The increase of solar cell efficiency via the implementation of a selective emitter in crystalline silicon solar cells is currently under research and partly in transition into production. The choice of the doping profile underneath the contacts can have significant impact on cell efficiency. In this work, the quantum efficiency of highly doped areas and its impact on the short circuit current are investigated. The aim of this work is to asses the influence of highly doped illuminated areas, which can possibly diminish the gain of the selective emitter structure regarding JSC. Areas of high doping are created by the technique of laser induced diffusion. The doping profile is varied by adjusting the laser pulse energy. The IV characteristics and spectral response of finished solar cells are measured. The internal quantum efficiency is analyzed using a model proposed by Fischer. Deeper diffused profiles are found to have larger dead layers and a linear correlation between the dead layer thickness and the resultant short circuit current is observed. The impact on solar cells with selective emitter is discussed.