With today’s record efficiency of 44.0 % under a concentration of 942 suns [38] III-V solar cells have not reached their full potential. The multi-junction concept has the perspective of obtaining efficiencies above 45 % and maybe even 50 % under concentration. New designs for cells with more than three junctions require the use of […]

One of the aims of ELO is to allow multiple reuse of the wafer after lift-off to reduce cell cost. Ideally, a minimum of wafer re-preparation between consecutive lift-offs is required. However, exposure to the HF solution increases the surface roughness of the wafer on a nanometer scale. The roughness is about 0.3 nm for […]

Wafer-based cells have a full area back contact. A thin-film cell allows access to the backside of the device. This makes it possible to apply a metal grid on front and back side. In this design the cell can be used as a bifacial cell [45] where illumina­tion takes place from both top and bottom […]

For space solar cells high efficiency, high radiation resistance, a low weight, and flexibility are the desired features. Because of their highest power output wafer – based III-V cells have been dominant over other cell types since the late 1990s. Wafer-based cells are mounted on a rigid honeycomb structure to prevent the wafers from breaking, […]

The first good quality thin-film III-V cell, a 4 cm2 GaAs cell with a 23.3 % efficiency, was made by Kopin in 1990 [25] at a time when the best wafer-based GaAs cell performance was 25.1 %. The thin-film was not lifted off chemically like in ELO but mechanically using the CLEFT (Cleavage of Lateral […]

Conventional triple junction cells grown on Ge have their limitations. They are inflexible, brittle, and relatively heavy. Therefore wafer-based cells require some kind of structural support to prevent damage. Thin-film III-V cells produced with the ELO technique offer new opportunities for device design, based on the fact that the thin-film carrier can be selected on […]

Alternative approaches for ELO are directed to the production of microchips using a transfer-printing technique to peel and print a large number of small thin-film structures onto glass or plastic [23]. The layer stack for this method is identical to other ELO methods: a device structure that is grown over an AlAs release layer, only […]

For the application of ELO the process needs to have a sufficiently high etch rate. It is and always will be a relatively slow process. With an etch rate of less than 1 mm/h it initially took more than a day to lift-off a 2 in. diameter thin-film structure. Therefore an important goal was to […]