Optimization of silicon pyramidal emitter by self-selective Ag-assisted chemical etching

Abstract

Optimization of a silicon pyramidal emitter by self-selective Ag-assisted chemical etching is explored with regard to solar cell applications. Increased sheet resistance and increased lifetime of the minority carriers together indicate that the emitter recombination is significantly reduced, as a result of minimizing the dead layer on the silicon surface. Scanning electron microscopy (SEM) images reveal that the peaked pyramid becomes rounded, alleviating the heavy phosphorus (P) diffusion at the peak of the pyramid. Moreover, the reflectivity of the silicon wafers increases a little after optimization due to the formation of the rounded pyramids, indicating that the emitter becomes more uniform as well. Such an optimization process will result in a minimized dead layer and uniform emitter, leading to decreased Auger recombination and enhanced efficiency of collecting electrons, which improves the open-circuit voltage (V_oc), short-circuit current density (J_sc), conversion efficiency (E_ff) and external quantum efficiency (EQE) of the solar cells significantly.