AbstractMicrostructured antireflective coatings (ARCs) can reduce reflection losses over a wide range of incidence angles when applied to the surface of a high‐efficiency III‐V photovoltaic cell in a concentrator photovoltaic (CPV) system. In this article, we present a microstructured ARC consisting of a monolayer of close‐packed silica microbeads partially submerged within a polydimethylsiloxane (PDMS) cell encapsulant for use within a reference 500× CPV submodule. Comparing a commercialized SiOx encapsulant to this microstructured coating with 25% submerged 1,000 nm‐diameter beads, angle‐dependent external quantum efficiency measurements yield a 2.6% current gain for the microstructured coating. Simulations demonstrate good agreement with measurements, predicting a 2.4% current gain for the same configuration. Extrapolating with our validated model, we estimate a maximum and achievable (within a large manufacturing tolerance) current gain of 3.4% and 2.9 ± 0.4% using 60% submerged and 10%–32% submerged 760 nm‐diameter beads, respectively.