All-back-Schottky-contact thin-film photovoltaics

The concept of All-Back-Schottky-Contact (ABSC) thin-film photovoltaic (TFPV) devices is introduced and evaluated using 2D numerical simulation. Reach-through Schottky junctions due to two metals of different work functions in an alternating, side-by-side pattern along the non-illuminated side generate the requisite built-in field. It is shown that our simulation method quantitatively describes existing data for a recently demonstrated heterojunction thin-film cell with interdigitated back contacts (IBCs) of one metal type. That model is extended to investigate the performance of ABSC devices with bimetallic IBCs within a pertinent parameter space. Our calculations indicate that 20% efficiency is achievable with micron-scale features and sufficient surface passivation. Bimetallic, micron-scale IBCs are readily fabricated using photo-lithographic techniques and the ABSC design allows for optically transparent surface passivation layers that need not be electrically conductive. The key advantages of the ABSC-TFPV architecture are that window layers, buffer layers, heterojunctions, and module scribing are not required because both contacts are located on the back of the device.