For organic light-emitting diodes (OLEDs), transparent singlecrystal-Si membranes were fabricated on a silicon-on-insulator (SOI) wafer. The SOI wafer included a buried layer of SiO 2 and Si 3 N 4 as an etch-stop layer. The etch-stop layer enabled fabrication of transparent single-crystal-Si membranes with various thicknesses, and the thinning technology is described For membranes with thicknesses of 72 and 5000 nm, the respective optical transmittances were 93%, and 9% for R (λ=660 nm), 91%, and 1 % for G (λ=525 nm), and 93%, and 0 % for B (λ=470 nm). Organic light-emitting diodes were then fabricated on transparent single-crystal-Si membranes with various top Si thicknesses. OLEDs with 72 and 5000 nm thick membranes and operating at 8.5 V observed luminance of 2260 and 123 cd/m 2 , respectively.