SILICON SOLAR CELLS: PHOSPHORUS EMITTER AND METAL - GRID OPTIMIZATION FOR HOMOGENEOUS (n~+p) AND DOUBLE-DIFFUSED (n~(++)n~+p) STRUCTURES

摘要

This work focuses on studying two types of structure: homogeneous (n~+) and double-diffused (n~(++)n~+) emitter solar cells. The emitter collection efficiencies and the recombination current densities were studied for a wide range of surface dopant concentrations (N_s= 1 × 10~(18)cm~(-3) to 1 × 10~(20)cm~(3)) and thicknesses (W_e=0.1μm to 10μm). The frontal metal-grid was optimized for each emitter, considering the dependence on the metal-semiconductor contact resistivity and on the emitter sheet resistance. Complete structures (n~+p and n~(++)n~+p) were analyzed and the output parameters (short-circuit current density, J_(sc); open-circuit voltage, V_∝; fill factor, FF and efficiency, η) were determined. The best efficiency for n~+p structures, η=25.5%, is found for emitters with thicknesses between W_c≈0.5μm-3μm and surface doping concentrations in the range N_s=2×l0~(19)cm~(-3)-4×l0~(18) cm~(-3); while for the n~++n~+p structure a maximum efficiency of η ≈ 26.0% was identified for an even wider range of emitter dopant profiles, 1×l0~(-18)cm~(-3) < N_s < 1 ×10~(19)cm~(-3) and 0.5μm < W_e < 10μm.