NOVELTY - A thin film III-V compound solar cell (103) free of substrate comprises active layer or several active layers (110A-110D); and backing layer (120) formed on active layer, where cell is formed on substrate and substrate is subsequently removed to leave solar cell free of the substrate. The active layer is formed of III-V compound. The solar cell further comprises surface grid metallization (140) formed on surface of active layer opposite backing layer; and antireflection coating (130) formed on surface of the active layer opposite the backing layer.    USE - As thin film III-V compound solar cell (claimed); as photovoltaic devices.    ADVANTAGE - The backing layer allows the wafer bonded thin film III-V compound solar cell to flex in at least two dimensions. The solar cell exhibits improved thermal conductivity; improved efficiency; increased flexibility; and is easy to handle. The solar cells are fabricated by a method that utilizes a removable and reusable substrate. The metalized layer, polymer layer or metal/polymer layer allows the solar cell to flex without being damaged. The solar cell can be fabricated by using a method that is applicable for large-scale fabrication.    DETAILED DESCRIPTION - A thin film III-V compound solar cell (103) free of a substrate comprises an active layer or several active layers (110A-110D); and a backing layer (120) formed on the active layer, where the thin film III-V compound solar cell is formed on a substrate and the substrate is subsequently removed to leave the thin film III-V compound solar cell free of the substrate. The active layer is formed of a III-V compound. The thin film III-V compound solar cell comprises a single junction thin film III-V compound solar cell solar cell; or a multiple junction thin film III-V compound solar cell solar cell. The solar cell further comprises surface grid metallization (140) formed on a surface of the active layer opposite the backing layer; and an antireflection coating (130) formed on the surface of the active layer opposite the backing layer. At least two of the several active layers are wafer bonded together. The solar cell includes gallium-arsenide (GaAs) active layer and gallium-indium-phosphide (GaInP) active layer; or gallium-indium-arsenide (GaInAs) active layer and a GaInAsP active layer; or a GaInAs active layer, a GaInAsP active layer, a GaAs active layer, an aluminum-gallium-indium-phosphide (AlGaInP) active layer, a GaInP active layer, AlGaInP active layer and a backing layer.    DESCRIPTION OF DRAWING(S) - The figure shows cross-sectional view of stack up of a wafer bonded thin-film multiple junction III-V compound solar cell.    Wafer bonded thin film multiple junction III-V compound solar cell (103)    First active layer (110A)    Second active layer (110B)    Third active layer (110C)    Fourth active layer (110D)    Backing layer (120)    Antireflection coating (130)    Metallized conductors (140)