High Ambient Contrast Ratio and Efficiency LED Display Devices Utilizing Inverted Packaging Structure

Abstract

Highly light-absorbed encapsulation is generally used to eliminate the ambient light for light-emitting diode (LED) display devices, it is challenging to simultaneously achieve a high ambient contrast ratio (ACR) and high light output efficiency (LOE). To solve this problem, we propose an inverted packaging structure for LED display devices. The LED chips’ emitting surface is mounted on the transparent carrier board (TCB) while the backside is packaged by the composite encapsulation, causing that the substrate is inverted to the topside of devices. As a result, the chips can emit light directly from the TCB and avoid the absorption loss of the encapsulation, leading to the high ACR and LOE performances. Compared to traditional devices, the inverted device showed an average increase of over 800% in luminous flux (LF) and LOE, and an average increase of over 390% in ACR. Additionally, the devices exhibited excellent soldering performance, corrosion resistance, airtightness, and thermal stability. This novel device overcomes the bottleneck of achieving both high ACR and high LOE, providing new insights for the development of LED display technology. Future work can further optimize the structure and materials of the TCB and composite encapsulation to enhance device performance.