High transmittance and deep RGB primary electrochromic color filter for high light out-coupling electro-optical devices.

We report a transmittance controllable electrochromic color filter (TCECF) by incorporating new electrochromic leuco dyes and their optimized composition. Each primary color red (R), green (G), and blue (B) electrochromic filter has an excellent transmittance of more than 84% at 650 nm, 540 nm, 450 nm, and the color coordinates are controllable from white (0.332, 0.347) to deep-red (0.621, 0.344), deep-green (0.327, 0.646), and deep-blue (0.179, 0.085), respectively. Also, each TCECF has good coloration efficiencies of 188.7 cm2 C-1 (R), 189.3 cm2 C-1 (G), and 147.8 cm2 C-1 (B) with high optical density change. A full color producible electrochromic color filter (ECF) is designed and fabricated by integrating primary RGB color filters with a refractive index matching adhesive layer. The fabricated three-stack full color producible ECF enables high transmittance of about 61% for clear white light extraction, and it can produce various colors including RGB. This TCECF technology will be very useful for high light out-coupling electro-optical applications, such as smart lighting, smart window, and display.

An accurate measurement of the dipole orientation in various organic semiconductor films using photoluminescence exciton decay analysis.

In this study, we report an accurate and more reliable approach to estimate the dipole orientation of emitters especially phosphorescence, fluorescence and even thermally activated delayed fluorescence. The dipole orientation measurements are performed by examining the variation of the photoluminescence (PL) exciton decay rate from time-resolved PL and optical analysis. Our anisotropic dipole orientation results are consistent with those of previous reports. The studied measurement approach is very reliable and accurate to estimate the dipole orientation of any organic semiconductor materials regardless of whether they are doped or neat films.

Highly efficient single-stack hybrid cool white OLED utilizing blue thermally activated delayed fluorescent and yellow phosphorescent emitters.

Highly efficient single-stack hybrid cool white organic light-emitting diodes (OLEDs) having blue-yellow-blue multiple emitting layers (EMLs) are designed and constructed by utilizing blue thermally activated delayed fluorescent (TADF) and yellow phosphorescent emitters. The out-coupling efficiencies of yellow and blue emissions are maximized by tuning the ITO and total device thickness that satisfies both of antinode positions for yellow and blue emissions in a limited multiple EML thickness. To obtain a cool white emission, the exciton formation ratio in the blue-yellow-blue multiple EML system is controlled by manipulating the recombination zone through charge conductivity variation of host medium in the blue TADF EML. The resulting device exhibits cool white emission with very high maximum external quantum efficiency of 23.1% and CIE color coordinates of (0.324, 0.337). We anticipate that the studied approach will raise the viability of single-stack hybrid cool white OLEDs for high performance display applications.

Next generation smart window display using transparent organic display and light blocking screen.

Transparent organic light emitting diodes (TOLED) have widespread applications in the next-generation display devices particularly in the large size transparent window and interactive displays. Herein, we report high performance and stable attractive smart window displays using facile process. Advanced smart window display is realized by integrating the high performance light blocking screen and highly transparent white OLED panel. The full smart window display reveals a maximum transmittance as high as 64.2% at the wavelength of 600 nm and extremely good along with tunable ambient contrast ratio (171.94:1) compared to that of normal TOLED (4.54:1). Furthermore, the performance decisive light blocking screen has demonstrated an excellent optical and electrical characteristics such as i) high transmittance (85.56% at 562nm) at light-penetrating state, ii) superior absorbance (2.30 at 562nm) in light interrupting mode, iii) high optical contrast (85.50 at 562 nm), iv) high optical stability for more than 25,000 cycle of driving, v) fast switching time of 1.9 sec, and vi) low driving voltage of 1.7 V. The experimental results of smart window display are also validated using optical simulation. The proposed smart window display technology allows us to adjust the intensity of daylight entering the system quickly and conveniently.