SPLTRAK Abstract Submission
Planar Transparent Conductive Oxide/Ag Rear Contacts for High Efficiency III-V Photovoltaics
Christopher T. Gregory, Sean J. Babcock, Richard R. King
Arizona State University, Tempe, AZ, United States

Photon recycling in photovoltaic devices can be attained by using highly reflective back surfaces. Some of the highest reflectance surfaces are composed of a plane of dielectric material deposited on a highly reflective metal such as Ag or Au. Although optically effective, the use of a planar dielectric layer complicates electrical contact to the device, leading to approaches such as point contacts. A simple solution—that may not result in significant optical or resistive losses—is to use a planar transparent conductive oxide (TCO) layer instead of a dielectric layer. This work investigates the viability of a such a contact. It is observed that contact resistivities of the TCO/Ag stack on a highly doped AlGaAs or GaAs contact layer are below 0.1 Ω cm2 for TCO doping concentrations on the order of 1019 cm-3. The contact resistivity can be reduced further by increasing the doping in the semiconductor layer. Internal hemispheric reflectances of the proposed contacts are expected to reach up to 98% at the wavelength of interest, facilitating photon recycling. The performance of this contact structure suggests use in technologies such as photonic power converters and thermophotovoltaics.