Epitaxial lift-off of gaas thi̇n films and transferring on to the flexible carriers for solar cell applications

Epitaxial lift-off (ELO) method has recently gained interest as a cost-effective innovative technology for the GaAs-based III-V group large area solar cell applications. The ELO method allows the separation and transferring onto the new cheap carriers (flexible plastics, Si susbtrate, glass etc.) of epitaxially grown III-V group semiconductor thin film electronic/optoelectronic device structures from the very expensive substrates. After the exfoliation and transfer of epitaxially grown active film, the substrate can be used for another consequtive epitaxial growth. In this thesis study, GaAs thin films grown by molecular beam epitaxy on GaAs susbstrates were lifted off and transferred onto the flexible plastic carriers for solar cell applications. After the development and improvement in ELO processes, thin films with 3 inch in size were transferred to the flexible carriers with a lift off speed of approximately 30 mm/h. As a practical appication; ELO technique was applied to the designed thin film GaAs solar cell structures which were grown by MBE method. The energy conversion and quantum efficiency values of the manufactured cells were measured in accordance with the measurement standards. As a result of the measurements; energy conversion efficiency values of 18.78% and 22.03% were achieved for flexible thin film GaAs cells and susbstrate based reference GaAs cells respectively.