Advances in Surface Passivation Schemes for High Efficiency c-Silicon Solar Cells

摘要

Effective surface passivation is one of the most important prerequisites for high efficiency crystalline silicon (c-Si) solar cells fabricated on thin wafers. To obtain, a good quality SiO2 films and SiO2/Si interfaces low temperature post oxidation annealing was carried out. Surface recombination velocity of 62 cm/s, a low interface trap density of 3 x 10(11) states/cm(2)/eV and fixed charge density was reduced to 1 x 10(11)/cm(2) due to the annealing at 500 degrees C. Similarly we analyzed and compared the optical and passivation properties of Al2O3/SiNx and Al2O3/SiONx stack layer. Silicon oxynitride (SiONx) has been used to improve antireflection and passivation properties since SiONx provides an excellent optical reflection than the conventional SiNx. Dielectric stack passivation layer of Al2O3/SiONx is preferred for high efficiency solar cell since SiNx is not suitable for p-type c-Si passivation due to the formation of an inversion layer. The effective lifetime of the Al2O3/SiONx stack has resulted in 0.85 ms after firing. The reference cell with Al2O3/SiNx stack shows an efficiency of 18.61% with V-oc of 614 mV. With optimized layer parameters, cells having Al2O3/SiONx stack shows an efficiency of 19.45% with V-oc of 626 mV, J(sc) of 40.53 mA/cm(2), and FF of 76.6%.