Energy Band Engineering for Improved Vertical Transport in Quantum Structured III-V p-i-n Solar Cells

Abstract

AbstractThe use of InGaAsN and GaBiAsN quantum structures in the intrinsic region of conventional III-V p-i-n solar cells, lattice matched to GaAs, presents several advantages for photovoltaic (PV) application. First they allow for very shallow to zero valence band offsets thus permitting the free movement of holes. Second, a wide range of band-gap values are made possible due to the large band gap decrease upon the introduction of minute amounts of N and Bi. Using band structure calculations that include the strain effects, conduction and valence band anti-crossing models describing the large band gap bowing and the transfer matrix method, we present the theoretical investigation of optimum design conditions for enhanced vertical transport. The direct quantum mechanical resonant tunneling of electrons out of the quantum structures and into the continuum of the conduction band of the host semiconductor material can be facilitated provided that an adequate choice of material parameters is made. The high electron transmission probability together with the free movement of quasi-3 D holes is predicted to result in enhanced PV device performance. Furthermore, the increase in electron effective mass due to the incorporation of N translates in enhanced absorptive properties, ideal for PV application.