非常荣幸能够担任光电所学会会长。首先要感谢光电所的各位同学，愿意给我一个机会为大家服务。在这里也要感谢江宏礼同学，以及潘昆懋同学，帮我处理了许多所学会以及实验室的事务，让我可以无后顾之忧。

从2007年的9月入学迄今，在光电所这个大家庭也度过了一年的光景。我想会让我担任所学会会长的原因有很多，最重要原因的在于，在光电所这一年生活当中，我和大家一起上课、做实验、踢球、联谊。几乎大部分的时间都是与同学们度过。我开心时，同学们总是愿意倾听分享我的喜悦；而在我失落遇到挫折时，身边的朋友们也带给我许多建议与鼓励。这段时间内，我感受到光电所的老师与同学们带给我的温情，让我了解自己是这个大家庭里的一份子，更希望自己也能为光电所尽一份心力，把自己体会到的喜悦带给大家。

有鉴于过去的一年中，常听到同学在讨论，相对于电资学院其它研究所而言光电所的活动实在太少，不免有些遗憾。因此在未来的一年中，所学会的重心将放在为同学们举办联欢活动，类型丰富，以期能够促进各实验室的感情。活动包括有餐会、运动比赛，以及艺文活动等，敬请期待，并请大家踊跃参与。同时我们期望能够建立起学生跟所办公室以及教授之间沟通的管道，让学生们能够对光电所的事务发表建议。

虽然跟光电所许多的前辈比起来，我无啻是个新人。但我愿以一颗充满热诚的心，在任期内全心奉献于所学会。也请光电所的每一份子不吝批评指教与协助，让所学会能够为大家提供最完美的服务。

FIG. 1a. Transmission change of as-grown SiO_1.25 and CO₂ laser annealed SiO_1.25 at Plaser=6 kW/cm². (Inset: Transmission spectra of pure quartz)

FIG. 1b. Absorption spectra of as-grown SiO_1.25 and CO₂ laser annealed SiO_1.25 at Plaser=6 kW/cm². (Inset: The calculated absorption spectra of Si₂₉H₂₄ and Si₂₉H₃₆)

FIG. 2. Optical band gap of CO₂ laser annealed SiO_1.25 as a function of laser intensity. (Inset: Tauc plot, (ahn) ^1/2 as a function of photon energy (hn) for as-grown SiO_1.25 sample and CO₂ laser RTA SiO_1.25 samples at Plaser from 6 to 12 kW/cm²)

FIG. 3a. PL spectrum of PECVD-grown SiO_1.25 annealed at CO₂ Plaser of 7.5 kW/cm² and transmission change of as-grown SiO_1.25 and CO₂ laser annealed SiO_1.25 at Plaser of 6 and 7.5 kW/cm².

Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices

Research groups of Prof. Hoang-Yan Lin and Prof. Jiun-Haw Lee

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

(e-mail) hylin@cc.ee.ntu.edu.tw

台湾大学光电所林晃岩教授

　We experimentally and theoretically investigated the optical characteristics of organic light-emitting devices (OLEDs), having different pixel sizes and attached with patterned microlens array films. For a regular microlens array (Fig. 1(b)), though it can extract the waveguiding light and increase luminous current efficiency for a large-pixelated OLED, we observed that it decreased the luminance to an even lower level than that of the planar OLED as its pixel size was close to the microlens dimension (Fig. 2). Although a microlens can effectively outcouple the light rays originally at incident angles larger than the critical angle, it also can impede the outcoupling for the light rays originally at incident angles smaller than the critical angle. Enhancement or reduction of the light extraction depends on the relative positions of the light emitting point and the microlens. Therefore, we proposed a center-hollowed microlens array (Fig. 1(c)), of which the microlenses directly upon the pixel are removed, and proved that it can increase the luminous current efficiency and luminous power efficiency of a small-pixelated OLED. As can be seen from Fig. 3, by attaching this patterned microlens array, 87% of luminance enhancement in the normal direction was observed for a 0.1´0.1 mm² OLED pixel. On the other hand, a regular microlens array resulted in 4% decrease under the same condition.

Electrical and Optical Characteristics of OLED with Bipolar Emitting Layer

Research group of Prof. Jiun-Haw Lee

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所李君浩教授

　One of the root causes which limits the operation lifetime of organic light-emitting device (OLED) is the charged carriers piled-up at the interface of transporting layer and emitting layer (EML). By introducing the bipolar EML, the recombination zone in an OLED becomes wider which effectively elongated the operation lifetime. We have demonstrated the performance improvement and studied the electrical and optical characteristics of OLEDs with bipolar EML quantitatively and qualitatively.

　We used high-electron-mobility ETL material, bis(10-hydroxybenzo[h] qinolinato)beryllium (Bebq₂), mixed with a-naphthylphenylbiphenyldiamine (NPB) as the bipolar EML. We have demonstrated an OLED with a luminance of 27600 cd/m² at only 5 V, and a lifetime four times longer than that of a conventional device. Since the recombination zone was wider, the maximum luminance in a bipolar OLED can be as high as 288000 cd/m² with the current density over 7 A/cm², which may be suitable for flashlight applications. Not only the performance improvement, we also discussed the carrier transport characteristics in a bipolar EML from current-voltage characteristics and the recombination process from the electro-luminescence measurement. We found an optimized mixing ratio which was NPB:Bebq2=1:1 with highest current density due to the electron-hole balance in this bipolar EML. The spectral shift was due to the recombination shift and the solid-state solvation effect.

　Besides, we used two different methods to quantitatively investigate the recombination zone in the MH-EML consisting of NPB and tris-(8-hydroxyquinoline) aluminum (Alq3). The first method was by using rigorous electrical and optical models to simulate the carrier distribution, recombination distribution, and EL spectra in the MH-OLED. By fitting the J-V curves and the spectra with different mixing ratios, the mobility values can be extracted. Electron (hole) mobility decreased (increased) monotonically with increasing the NPB ratio. However, the driving voltage increased then decreased due to the competition between the hole-current enhancement and the electron-current decline. For the second method, we used a thin 4-(dicyanomethylene)-2-tert-butyl-6-1,1,7,7-(tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) layer with the thickness of 1.2 nm and the volume concentration of 2% as a probe to determine the recombination zone. Besides, we also found that when the probe position overlapped the maximum recombination position, a voltage reduction of 1.97 V was observed. It can be well explained by the enhancement of the recombination current from the continuity equation. This result suggested that the driving voltage of an OLED with the bipolar EML can be reduced by inserting a dopant in a suitable region. A white OLED was fabricated with selectively doping a yellow dopant in the blue EML which exhibits high efficiency and low driving voltage.

摘要

在蓝光磷光组件的开发上，高三重态能阶主体材料是一项重要关键。故我们首先研究具有高三重态能阶之电洞传导材料与电子传导材料，以及高效率之蓝光磷光组件结构。次一主题是探讨新型多功能主体材料；其后并具体实现单层之高效率红光磷光组件。接着藉由高三重态能阶双极性传导材料之开发，成功地将高效率单层磷光组件推展到绿光与蓝光。此外，我们对于使用磷光主体材料以利用偶极矩作用能量转移机制之组件亦有探讨。本论文最后则研究混合荧光与磷光之白光有机发光组件，以期能实现固态照明之应用。