Residual stresses and mechanical properties of thin film photovoltaic materials

Thin film solar cells;mechanical performance

Antartis, Dimitrios ; Chasiotis ; Ioannis

关键词: Thin film solar cells;    mechanical performance;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/34218/Antartis_Dimitrios.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The mean and gradient residual stresses and the failure behavior of individuallayers in inorganic thin film photovoltaics were investigated. The thin film photovoltaicsconsisted of an amorphous silicon (Si) p-n junction diode, a zinc oxide (ZnO)Transparent Conductive Oxide (TCO) layer (each 1μm thick), a Kapton® polyimidelayer acting as the bottom cathode and a thick aluminum substrate. Analysis of straightblister delaminations in the p-n junction layer and telephone cord type delaminations inthe p-n junction-TCO bilayer provided the mean residual stress values in the Simonolayer and the Si/ZnO bilayer, which were -466±118 MPa and -661±93 MPa,respectively. High aspect ratio freestanding strips of the Si/ZnO bilayer and the Simonolayer were used to determine the residual stress gradient using curvaturemeasurements. The stress gradient in the Si monolayer layer was 274±20 MPa/μm whilethe stress gradient in the Si/ZnO bilayer resulted in a maximum tensile stress value of360±27 MPa at the top of the ZnO layer and a maximum compressive stress of 319±24MPa at the bottom surface of the Si layer. The monolayer and bilayer strips were alsosubjected to uniaxial tension with a microscale tension apparatus to determine the failurestrength and the elastic modulus of each layer. The elastic modulus of the amorphous Simonolayer was 94±6 GPa, which is in agreement with bulk values. The bilayer strips, hadan elastic modulus of 107±7 GPa which provided a value of 120±13 GPa for the Young’smodulus of the ZnO layer, and tensile strength that was significantly lower than the Simonolayer. These results indicated poor adhesion and load transfer between theamorphous Si and the ZnO film and a mechanically weak ZnO film. Finally, proof ofconcept experiments were conducted with photovoltaic cells attached to carbon fibercomposites, which showed extensive fragmentation of the thin film photovoltaicsoccurring at small strains without though significant loss of functional performance of thecells until ~3% strain in the composite laminate.