High Performance Active-Matrix Light-Emitting Displays Enabled by Vertical Light-Emitting Transistor Technology

Opportunities for cost-effective manufacturing of fully printed high performance displays enabled by vertical light-emitting transistor pixels

“…Because the VOLET's channel length is simply the thickness of the deposited semiconductor layer, it is possible to achieve sub-micron channel length without high resolution patterning techniques. The resulting short channel length combined with the large cross-sectional area through which that current flows (figure 1) imbues the device with such a high current capability that even very low mobility semiconductors can now serve as the channel layer [61][62][63][64][65]. Note the distinction from the lateral channel TFT where the cross-section for current flow is confined to just a few nanometers above the gate dielectric interface across the width of the channel.…”

“…Thus, the device can be tailored to excel in many performance metrics. With the channel semiconductor and layers below it being transparent, including the CNT network source electrode which has a 98% transmittance throughout wavelengths of visible spectrum, the VOLET can readily be configured as a bottom emission device, avoiding the need for a transparent cathode and allowing for easier processing (figure 1) [64].…”

“…In addition to the intrinsic performance advantages, the integration of functionalities by the VOLET brings further advantages when it is situated in a bottom emission AMOLED pixel (figure 5) [64]. Since the VOLET emits light across its entire aperture, while simultaneously featuring built-in light emission control as well as intrinsic gate capacitance for charge storage between refresh cycles, the pixel real-estate that would normally accommodate the dr-TFT and the storage capacitor in a conventional AMOLED pixel becomes available for the VOLET, increasing the aperture ratio of the pixel.…”

“…Both OLED emitters and QLED emitters can be used on top of the channel layer to build the VOLET. Full color displays can be achieved using either Individual RGB VOLET light emitting pixels, or using a common emitter for all subpixels with color-forming layers to generate color, including White OLED plus color filters as well as blue OLED plus quantum dot color conversion layers [61][62][63][64]. All layers being flexible positions the VOLET well for flexible displays should flexible substrates be used.…”

“…The vertical organic light-emitting transistor (VOLET) provides a much-needed solution to this roadblock. It introduces a novel device architecture that circumvents the issues faced by the backplane manufacturing challenge to printed electronics [58][59][60][61][62][63][64][65]. As an integrated device that stacks light emitting layers directly atop the brightness-controlling functional structure, the VOLET itself is compatible with printed electronics processes.…”