Recently, ‘Liquid crystal display (LCD) vs. organic light-emitting diode (OLED) display: who wins?’ has become a topic of heated debate. In this review, we perform a systematic and comparative study of these two flat panel display technologies. First, we review recent advances in LCDs and OLEDs, including material development, device configuration and system integration. Next we analyze and compare their performances by six key display metrics: response time, contrast ratio, color gamut, lifetime, power efficiency, and panel flexibility. In this section, we focus on two key parameters: motion picture response time (MPRT) and ambient contrast ratio (ACR), which dramatically affect image quality in practical application scenarios. MPRT determines the image blur of a moving picture, and ACR governs the perceived image contrast under ambient lighting conditions. It is intriguing that LCD can achieve comparable or even slightly better MPRT and ACR than OLED, although its response time and contrast ratio are generally perceived to be much inferior to those of OLED. Finally, three future trends are highlighted, including high dynamic range, virtual reality/augmented reality and smart displays with versatile functions.

Emission mechanisms for OLEDs and their characteristics.

Sunlight readability is a critical requirement for display devices, especially for mobile displays. Anti-reflection (AR) films can greatly improve sunlight readability by reducing the surface reflection. In this work, we demonstrate a broadband moth-eye-like AR surface on a flexible substrate, intended for flexible display applications. The motheye-like nanostructure was fabricated by an imprinting process onto a flexible substrate with a thin hard-coating film. The proposed nanostructure exhibits excellent AR with luminous reflectance <0.23% and haze below 1% with indistinguishable image quality deterioration. A rigorous numerical model is developed to simulate and optimize the optical behaviors. Excellent agreement between the experiment and simulation is obtained. Meanwhile, the nanostructure shows robust mechanical characteristics (pencil hardness >3 H), which is favorable for touch panels. A small bending radius (8 mm) was also demonstrated, which makes the proposed nanostructure applicable for flexible displays. Additionally, a fluoroalkyl coating was applied onto the moth-eye-like surface to improve the hydrophobicity (with a water contact angle >100°). Such a self-cleaning feature helps protect touch panels from dust and fingerprints. The proposed moth-eye-like AR film is expected to find widespread applications for sunlight readable flexible and curved displays.

In this letter, we present and analyze the device performance of the mixed host ͑MH͒ organic light-emitting devices ͑OLEDs͒. The host of the emitting layer ͑EML͒ material in this device consists of a hole transport layer ͑HTL͒ and an electron transport layer ͑ETL͒ fabricated by coevaporation. The bipolar transport characteristic of the MH layer helps to reduce the driving voltage. Device lifetime is increased due to the elimination of the sharp boundary of the HTL/EML interface. Combining the MH structure with a high mobility electron ETL material, bis͑10-hydroxybenzo͓h͔qinolinato͒beryllium, the OLED has shown a brightness of 27 600 cd/ m 2 at a driving voltage of 5 V, and a lifetime four times longer than that of a conventional OLED.

The authors report the investigation of the charge transport behaviors in mixed thin films of N , NЈ-diphenyl-N , NЈ-bis͑1-napthyl͒-1,1Ј-biphenyl-4 , 4Ј-diamine and tris͑8-hydroxyquinoline͒ aluminum. The extracted electron and hole drift mobility were found to be sensitive to the compositional fraction and interpreted by energy levels, charge mobilities of neat compounds, and microscopic networks within the mixed systems. The carrier conduction characteristics, therefore, were used to illustrate the electrical and optical properties of the organic light emitting devices with a mixed layer and present direct evidences on the role of the mixed layer in these devices.