Avoiding Shading Losses in Concentrator Photovoltaics Using a Soft-Imprinted Cloaking Geometry
Shading losses are a longstanding obstacle in photovoltaic devices, particularly in concentrator photovoltaics, where the tradeoff between shading and resistive losses limits the concentration at which the highest power conversion efficiency is achieved to values far below the capabilities of concentrator optics. Here, we demonstrate a simple and scalable fabrication method that enables large front metal coverage while keeping shading losses to a minimum. Soft-imprint lithography is used to create trenches in a transparent polymer above the metal contacts, enabling cloaking via refraction at a range of angles near normal incidence. Using optical characterization techniques, we first confirm that the metal contacts are indeed optically cloaked. We then demonstrate an increase in short-circuit current density from 29.95 to 39.12 mA/cm2 for a Si solar cell with 25% front metal coverage before and after patterning, respectively. We investigate the angular performance of the trench pattern and further demonstrate how such a cloaking strategy could be implemented in concentrator photovoltaics to enable efficiency peaks at concentrations beyond 1000 suns.