Phase behaviors of NPB molecule under vacuum

Shim, Seob; Kim, Jin‐Tae; Shin, Eun Myoung; Chung, Nak-Kwan; Ko, Moon Kyu; Kwon, Ohyun; Yun, Ju‐Young

doi:10.1016/j.materresbull.2016.01.054

Cited by 4 publications

(2 citation statements)

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“…Visible light has a wavelength of several hundred nanometers, hence NLA with a diameter of several hundred nanometers is required to achieve the desired properties of blue TOLEDs. The recent study has reported that, even though the NPB melting temperature is constant at 280 °C regardless of the pressure, the boiling temperatures decrease linearly with the decrease in the pressure from 10 2 to 10 –2 Torr . This indicates that lower pressure conditions (down to 10 –2 Torr) in the vaporizer provide higher NPB vapor pressures.…”

Section: Results and Discussionmentioning

confidence: 97%

“…The recent study has reported that, even though the NPB melting temperature is constant at 280 °C regardless of the pressure, the boiling temperatures decrease linearly with the decrease in the pressure from 10 2 to 10 −2 Torr. 32 This indicates that lower pressure conditions (down to 10 −2 Torr) in the vaporizer provide higher NPB vapor pressures. Figure 1a (10 −1 Torr, ∼100 nm) and 1b (5 × 10 −2 Torr, ∼150 nm) shows that larger hemispherical nanolenses are obtained by decreasing the vaporizer pressure.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Optical Analysis of Power Distribution in Top-Emitting Organic Light Emitting Diodes Integrated with Nanolens Array Using Finite Difference Time Domain

Han

Park

Cho

et al. 2018

ACS Appl. Mater. Interfaces

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Recently, we have addressed that a formation mechanism of a nanolens array (NLA) fabricated by using a maskless vacuum deposition is explained as the increase in surface tension of organic molecules induced by their crystallization. Here, as another research using finite difference time domain simulations, not electric field intensities but transmitted energies of electromagnetic waves inside and outside top-emitting blue organic light-emitting diodes (TOLEDs), without and with NLAs, are obtained, to easily grasp the effect of NLA formation on the light extraction of TOLEDs. Interestingly, the calculations show that NLA acts as an efficient light extraction structure. With NLA, larger transmitted energies in the direction from emitting layer to air are observed, indicating that NLAs send more light to air otherwise trapped in the devices by reducing the losses by waveguide and absorption. This is more significant for higher refractive index of NLA. Simulation and measurement results are consistent. A successful increase in both light extraction efficiency and color stability of blue TOLEDs, rarely reported before, is accomplished by introducing the highly process-compatible NLA technology using the one-step dry process. Blue TOLEDs integrated with a N, N'-di(1-naphthyl)- N, N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine NLA with a refractive index of 1.8 show a 1.55-times-higher light extraction efficiency, compared to those without it. In addition, viewing angle characteristics are enhanced and image blurring is reduced, indicating that the manufacturer-adaptable technology satisfies the requirements of highly efficient and color-stable top-emission displays.

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Section: Results and Discussionmentioning

confidence: 97%

Section: ■ Results and Discussionmentioning

confidence: 99%