Simulation and partial prototyping of an eight‐junction holographic spectrum‐splitting photovoltaic module

Spectrum‐splitting photovoltaics incorporate optical elements to separate sunlight into frequency bands, which can be targeted at solar cells with bandgaps optimized for each sub‐band. Here, we present the design of a holographic diffraction grating‐based spectrum‐splitting photovoltaic module integrating eight III‐V compound semiconductor cells as four dual‐junction tandems. Four stacks of simple sinusoidal volume phase holographic diffraction gratings each simultaneously split and concentrate sunlight onto cells with bandgaps spanning the solar spectrum. The high‐efficiency cells get an additional performance boost from concentration incorporated using a single or a compound trough concentrator, providing up to 380X total concentration. Cell bandgap optimization incorporated an experimentally derived bandgap‐dependent external radiative efficiency function. Simulations show 33.2% module conversion efficiency is achievable. One grating stack is experimentally fabricated and characterized. Spectrum‐splitting photovoltaics use an optical element to separate different frequency bands of light and send them to solar cells with bandgap energy best tuned to use that band of light, enabling more subcells than can be included in traditional tandem multijunction architectures. Here, we use a holographic spectrum splitter featuring twelve holographic optical elements to split light onto eight high‐efficiency III‐V alloy solar cells of bandgaps spanning the solar spectrum. We describe our design and optimization process using optoelectronic modeling, including an experimentally grounded, bandgap‐dependent external radiative efficiency model; experimental measurements of hologram stacks guide the analysis.