Electro-optical Optimization of C-si Thin Solar Cells Patterned by Photonic Crystals

Using Photonic Crystals (PC) to pattern the top surface of thin film solar cells aims at increasing absorption in the red part of the solar spectrum. In this conference, we explain that a PC also introduces new optical properties for high energy photons since they can be channeled through the holes of the PC itself. Then, optical intensity at the corresponding wavelength is mainly located into the air (or cladding media), leading to a lower effective absorbing constant compared to the bulk material. In other words, these photons can be absorbed further from a carrier collector located at the surface, where carrier recombinations are elevated due to a high doping level. Unfortunately, surface recombinations are even more critical since the residual absorption of the channeled photons is mainly located on the lateral surface of the holes. In this communication, we focus on the influence of the junction location, the shape of the top contact doping profile (conformal or not) and on the influence of the surface passivation to obtain a robust devices.