Near-white appearance solar cells enabled by nanoclay-based scattering layers

Building-integrated photovoltaics (BIPVs) require both high power conversion performance and an aesthetically acceptable appearance, particularly near-white façades that are widely used in architecture. However, conventional whitening methods based on surface-textured glass or highly scattered pigment layers can cause considerable optical losses. In this study, we proposed a scattering layer using nanosized smectite clay and investigated its potential for realizing near-white solar cells with reduced power loss. Organically modified smectite was dispersed in a thermoplastic acrylic resin and spin-coated onto glass to form clay films with controlled clay volume fractions. When applied to Si heterojunction (SHJ) cells, the clay films provide high haze through volume scattering, while maintaining a hemispherical transmittance close to that of flat glass, resulting in very low optical loss. In particular, a 50 vol% clay film achieved a near-white appearance comparable to that of commercial textured glass diffusers, while maintaining an optical loss below 1% with a lightness of 32. We also designed and fabricated hybrid films combining clay with dielectric multilayer films (DMFs), optimized by multi-objective Bayesian optimization. The optimized clay–DMF hybrid films achieved a lightness of approximately 60 with an optical loss of approximately 11%, exhibiting a color tone closer to white. These results demonstrate that nanoclay-based scattering layers and their hybridization with DMFs could offer a promising approach for producing near-white BIPV modules with enhanced aesthetic quality while retaining acceptable power performance. • BIPVs require high power conversion and an aesthetically acceptable appearance. • However, conventional whitening methods can cause considerable optical losses. • Hybrid films that combined nanoclay with dielectric multilayer films were studied. • 50 vol% clay film exhibited near-white appearance with optical loss <1% in SHJ cells. • Optimized clay–DMF hybrid films exhibited L∗ ≈60 at ∼11% optical loss.