A vertical organic light-emitting transistor (VOLET) was fabricated by stacking a capacitor cell on top of an organic light emitting cell joined by a common source electrode，and the operation mechanism was analyzed. This unique device has the dual functions of emitting light as an OLED and switching current as a transistor. When the capacitor is under bias, the stored charges on the thin and coarse electrode shared by the two units modulate the charge injection of the OLED active unit, hence control the current flow and consequently tune the light emission. This device structure provides an extremely short channel in the nanometer range and a large conduction area (004 cm2), which supply enough output current (up to 02 mA) to drive the light emitting unit. As a result, thanks to the vertical integration, this device not only realizes multifunction but also operates at lower voltage, which provides a navel solution for the active-matrix OLED display application.