CEA, LITEN, 17 Rue des Martyrs, Grenoble, France, CEA, LETI, MINATEC, 17 Rue des Martyrs, Grenoble, France

Cu(In, Ga)Se2 (CIGS) based thin film solar cells have been extensively studied and today, power conversion efficiencies higher than 20% have been demonstrated on both rigid and flexible substrates. However, very little is known about the mechanical resistance of flexible CIGS solar cells under flexion. Here we report an original study on the mechanical properties of CIGS solar cells fabricated on 100 µm-thick ultra-thin glass substrates. The Young's modulus and hardness of Mo and CIGS thin films are measured by nanoindentation, a technique well adapted to the characterization of thin film materials. Young's modulus values of 289 GPa and 70 GPa are obtained for the Mo and the CIGS layers respectively, as well as a CIGS hardness of 3.4 GPa. These values, combined with an analytical model, allow calculating the strain induced in thin film during the flexion of solar cells fabricated on ultra-thin glass substrate as well as on polyimide substrate. Thereby, we show that using a substrate with a low thickness and a low Young's modulus enables to lower the thin films strain during the flexion of cells. © 2016 Elsevier B.V.

Cu(In,Ga)Se2, Flexible, Hardness, Nanoindentation, Strain, Young's modulus

Bending (forming), Biomechanics, Copper, Elastic moduli, Films, Gallium, Gallium alloys, Glass, Hardness, Mechanical properties, Nanoindentation, Nanostructured materials, Semiconducting selenium compounds, Solar cells, Strain, Substrates, Thin films, Cu (in ,ga)se, Flexible, Low young's modulus, Mechanical resistance, Polyimide substrate, Power conversion efficiencies, Rigid and flexible substrates, Thin film material, Thin film solar cells