Enabling thin silicon technologies for next generation c-Si solar PV renewable energy systems using synchrotron X-ray microdiffraction as stress and crack mechanism probe

Abstract

Recently, there has been a strong commercial push toward thinner silicon in the solar photovoltaic (PV) technologies due to the significant cost reduction associated with it. Tensile stress (normal, in-plane) and fracture of the silicon cells are increasingly observed and reported for products of crystalline solar cell technologies. In an effort to shed light on these topics, stress measurements and mapping of the solar cells in the vicinity of the most typically observed crack initiation locations using synchrotron X-ray microdiffraction technique was conducted and are reported in this paper. The technique is unique as it has the capabilities to quantitatively determine stresses in silicon and to map these stresses with a micron resolution, all while the silicon cells are already encapsulated.With this technique, we aim to gain fundamental understanding of the stress magnitudes as well as characteristics that could lead to crack initiation and propagation. We have thus far found evidences of both extrinsic (device related) as well as intrinsic (crystallographic) nature of silicon cracking, which further confirm that the control of mechanical stress is the key to enable thin silicon solar cell technologies in the coming years. This study represents an ongoing high impact technology research that addresses real and important fundamental materials issue facing the crystalline silicon solar PV industry and contributes directly to the industry drive to reduce cost of PV systems to grid parity.