A universal surface texture by solution coating

In this paper we propose a 'build-up' approach for surface texturing on solar cells. By coating solar cells with a monolayer of dielectric microparticles, followed by a dielectric film with a thickness less than the height of the particles, a surface texture can be formed on almost any type of solar cells. More importantly, this texture is prepared by solution coatings, ensuring its low cost. Dielectric particles of various shapes, spherical, pyramidal and conical, can all be used. Current experiments focus on spherical silica microparticles partially immersed in a spin-on glass film. It has been demonstrated that the spherical texture improves the transmittance of quartz substrate between 400 and 1,100 nm and in the incident-angle range of surface normal to at least 30°. Extensive modeling has been performed to optimize the design of and to find the process windows for the coatings. Recent progress includes uniform monolayer coating of silica microparticles on substrates of 6×6 in² in size by a convective process. Remaining challenges in integration of this texture into solar cells include: 1) index matching with top glass cover and existing antireflective coating; 2) cost-effective synthesis of index-matched dielectric microparticles and 3) large-area uniform coating of monolayer particles on rough poly-Si substrates.