# Quantum Dot-Based White Organic Light-Emitting Diodes Excited by a Blue OLED
## 1 Introduction  
Flourishing white organic light-emitting diodes (OLEDs) are vital for future solid-state lighting devices and full-color displays [1]. The quantum dot (QD) OLED is one of the most popular OLEDs today because of its wide color space, wide viewing angle, and other benefits it provides [2]. The emission wavelengths of QDs can be adjusted by the altering the size of the QDs, and the quantum efficiency of their photoluminescence (PL) is high. They have a high absorption capacity at blue wavelengths and offer high conversion efficiency. Therefore, QDs can be used as perfect color conversion materials [3]. Due to the feasibility of the solution process of the QD layer, the color tuning of the QD material, the narrow FWHM of the emission spectrum, the high luminous efficiency, and the fact that QDs areinorganic materials means that they have a useful life that is longer than organic ones. QD materials have proven that their advantages have great potential for next-generation displays. As a color conversion material, QDs can be used as a color enhancement film (QDEF) in the backlight of an LCD screen or as a quantum dot color filter (QDCF) in an OLED screen to expand the screen's color space [4; 5]. A QD has discrete electronic states, like natural atoms, and its electronic wave function is somewhat similar to that of an atom. They are often referred to as artificial atoms [6]. QDs are widely applicable in a variety of fields due to their highly tunable properties. They could potentially be used in electronic technologies and display technology, for example, in solar cells, photodetectors, photodiodes, field-effect transistors, biological systems, flat-panel TV displays, digital cameras, mobile phones, and gaming equipment [7; 8; 9; 10; 11; 12; 13]. Many studies are being conducted on quantum dot units, yet few provide information on how the device or process architecture might contribute to the overall color space [14]. For example, [PERSON] et al., from Jilin University, used CdSe/ZnS quantum dot material mixed with polymethylmethacrylate (PMMA) to create a separate composite film to convert a blue OLED to a white color, producing a white OLED with a maximum luminance of 10,250 cd/m\({}^{2}\) and maximum current efficiency of 20.6 cd/A. In the case of white the OLED, the CIE coordinates shifted only from (0.291, 0.406) at 4 V to (0.288, 0.405) at 8 V. This showed a relatively high degree of spectral stability under voltage variations. In addition, by integrating ordered microcylinder arrays with down-conversion films by transfer imprint, the viewing characteristics, and light extraction performance were improved for white OLEDs [15]. [PERSON] et al. from Yonsei University, South Korea, used red and green quantum dot materials mixed with PGMEA and positive photoresist and exposed and developed the technology on a glass substrate to create a full-color OLED display. Compared with conventional OLED displays, after using QDs, the light intensity of the white OLED in the red and green sub-pixels increased by 32.1% and 9.6%, respectively. After that, an air-gapped bridge structure was added between the OLED and the QDs to achieve a full internal reflection (FIR) that performed an optical cycle to improve the QDs' color conversion efficiency. The light intensity of the red and green sub-pixels increased by 58.2% and 16.8%, respectively, and due to the narrow emission spectrums of the QDs, the color space of the proposed OLED screen increased by 65%, from 5% to 75.9% [16]. [PERSON] et al. Hongik University in South Korea investigated the color conversion properties of QDs/OLEDs using the microcavity effect, with OLEDs fabricated on WO\({}_{3}\)/Ag/WO\({}_{3}\) (WAW) anodes. WAW devices with different thicknesses have different color coordinates due to the resonant cavity effect. As an example, when the WO\({}_{3}\) material possesses 120 nm of thickness, its coordinates for white light are (0.31, 0.37) [17].