For applications such as solar cells and displays, transparent single-crystal Si membranes were fabricated on a silicon-on-insulator (SOI) wafer. The SOI wafer included a buried layer of SiO2 and Si3N4 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 18, 72 and 5000 nm, the respective optical transparent were 96.9%, 93.7% and 9% for R (red, lambda = 660 nm), 96.9%, 91.4% and 1% for G (green, lambda = 525 nm), and 97.0%, 93.2% and 0% for B (blue, lambda = 470 nm). Organic light-emitting diodes (OLEDs) were then fabricated on transparent single-crystal Si membranes with various top Si thicknesses. OLEDs fabricated on 18, 72 and 5000 nm thick membranes and operated at 6 V demonstrated a luminance of 1350, 443 and 27 cd m(-2) at the current densities of 148, 131 and 1.5 mA cm(-2), respectively.