A NEW P(A-SiN:H/A-Si:H)-I(A-Si:H)-N(A-Sic:H/A-Si:H) Superlattice Solar Cell

Abstract

The objective of this work is (1) the evaluation and control of the Fermi level position in an amorphous hydrogenated silicon p-i-n Solar Cell through its carbon (or nitrogen) alloy n-and p-contact regions. The Fermi levels in both p- and n-regions of a P(a-Si:H/a-Si0.8N0.2:H)- i - N(a-Si:H./a-Si0.5C0.5:H) superlattice solar cell are computed. (2) prediction of open-circuit voltage values for this novel device. The p- and n- regions are replaced by superlattices, in which the Fermi levels in the wide gap barrier regions are, on an absolute scale, closer to the valence band or conduction band edges of the low band gap material (a-Si:H). In order for the p- and n- superlattices to yield a larger built-in voltage, the density of states in the doped wide band gap material, must be much greater, and the Fermi level of the wider band gap layer has to be closer to the corresponding band edge than that of the undoped low gap quantum well. Hence, the wide gap material must be heavily doped and have effective tails wider than that of the undoped low band gap material. As a result, the final Fermi level will lie between the corresponding bulk Fermi levels of the layers of the superlattice.