Investigations on the mechanical properties of the elementary thin films composing a CuIn 1−x Ga x Se 2 solar cell using the nanoindentation technique

Abstract

In this investigation, the mechanical properties of the different layers composing a CuIn 1 − x Ga x Se 2 (CIGS) based solar cell were studied. Magnetron sputtering technique was used for the deposition of these layers except for the cadmium sulphide (CdS) layer which was deposited using chemical bath deposition process. We performed several indentation tests on the individual layers, i.e. molybdenum (Mo) back contact layer, CIGS absorber layer, CdS and alternative zinc sulphide oxide (ZnOS) buffer layers, and zinc oxide (ZnO)-AZO (aluminium-doped zinc oxide) transparent window layer; all were deposited on glass substrates. We report the values of the hardness (H) and of the Young's modulus (E) for each material, using indentation tests and an analytical model. The Mo layer remained the hardest and the most rigid, with H = 8.7 GPa and E = 185 GPa, while the CIGS layer has shown poor mechanical properties with H = 3 GPa and E = 58 GPa. On the other hand, the observed similarity in mechanical properties of the ZnO and ZnOS layers might be attributed to the similarity of their microstructures.

Identification of the elastic-plastic properties of CrN coating on elastic-plastic substrate by nanoindentation using finite element method-reverse algorithm

“…The same model was used to determine Young's modulus of the coating and of the substrate, considering C as a variable depending on the material [2,27]. This constant was lower than the value used for the determination of the hardness since the elastic zone extended further than the plastic zone.…”

“…Difficulties in measuring the mechanical properties of thin films by classical methods have led to the use of the indentation method in nanoscale. Although nanoindentation technique has attracted considerable attention in recent decades, one of the main issues affecting the measurement of properties of the thin film by this technique is the substrate effect [1][2][3][4][5][6].Generally, to prevent this problem, a common practice is to consider that the modulus of the thin film is not affected by the substrate for indentation depths smaller than 1/10 of the film thickness [7]. Then, Young's modulus (E) and hardness (H) of the film can be obtained through Oliver & Pharr method [8].…”

Review on mechanical behavior of solar cells for building integrated photovoltaics

“…Zbib et al [81] found that the elastic modulus of polycrystalline silicon solar cell particles processed by a fluidized bed reactor was approximately 160 GPa according to the nanoindentation technique. Abib et al [82] demonstrated the mechanical properties of each layer of CIGS solar cells using the nanoindentation technique combined with the JH model. They found that the Mo layer had the highest hardness and stiffness, 9.7 GPa and 185 GPa, respectively.…”

“…They found that the Mo layer had the highest hardness and stiffness, 9.7 GPa and 185 GPa, respectively. The hardness and stiffness of the CIGS layer were only 3 GPa and 58 GPa [82]. Jin et al [83] measured the mechanical properties of gallium arsenide crystals used in solar cells by the nanoindentation technique.…”