Mark O. Liu

Lifetime Improvement of Organic Light Emitting Diodes using LiF Thin Film and UV Glue Encapsulation

This work demonstrates the use of lithium fluoride (LiF) as a passivation layer and a newly developed UV glue for encapsulation on the LiF passivation layer to enhance the stability of organic light-emitting devices (OLEDs). Devices with double protective layers showed a 25-fold increase in operational lifetime compared to those without any packaging layers. LiF has a low melting point and insulating characteristics and it can be adapted as both a protective layer and pre-encapsulation film. The newly developed UV glue has a fast curing time of only 6 s and can be directly spin-coated onto the surface of the LiF passivation layer. The LiF thin film plus spin-coated UV glue is a simple packaging method that reduces the fabrication costs of OLEDs.

Efficiency Improvement of Organic Solar Cells by Slow Growth and Changing Spin-Coating Parameters for Active Layers

The derivatives of C60, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and 3-hexylthiophene (P3HT) were dissolved in o-dichlorobenzene (DCB) solvent, and then spin-coated as an active layer for polymer solar cells. The experimental parameters including the spin-coating speed and drying conditions for the active layer, were studied carefully to obtain the optimum power conversion efficiency (PCE). In the active layer drying procedure, the DCB solvent saturated/unsaturated vapor pressure was adjusted by controlling the amount of solvent at a half-open capacity. The DCB solution was used to enhance the self-organization of the active layer of P3HT and to reduce the number of pure PCBM clusters. In the DCB optimum solution, the PCE of a polymer solar cell can be increased from 1.36 to 1.79%. The structure corresponds to a nano-to-micron scale ordering in the unsaturation-treatment films. In the optimum unsaturation procedure, the PCE of a polymer solar cell can be increased from 1.79 to 2.53%. Using two steps with optimum rotation speeds in the active layer spin-coating, the surface uniformity can be improved, with the PCE increased from 2.53 to 3.13%.

Comparison of Different Encapsulating Adhesives to Enhance the Efficiencies and Lifetimes of Polymeric Solar Cells

Polymeric solar cells (PSCs) with a derivative of C60 [[6,6]-phenyl C61-butyric acid methyl ester (PCBM)], and 3-hexylthiophene (P3HT) as active layers have been fabricated. The PSC devices were also packaged with glass and novel UV glues to improve their lifetimes and power conversion efficiencies (PCEs). After encapsulation with UV glue I, II, and III, the PCEs of PSCs reached 4, 4.82, and 6%, respectively, and their half-lifetimes increased to 16–18, 26–28, and 90 h, respectively, while the PCEs and half-lifetimes of PSCs without encapsulation were 3.76% and 2.5 h, respectively.

CHARACTERIZATION OF LOW COST ORGANIC PHOSPHOR FOR WHITE LIGHT-EMITTING DIODE

In this work, we prepared an organic phosphor and investigated its thermal as well as fluorescent properties. The experimental results reveal that lab-made organic phosphor exhibits excellent thermal stability (Decomposition temperature (Td) = 374 °C) and good fluorescent quantum yield (Φ = 0.88). The organic phosphor was then coated onto the blue LED chip to form a white light-emitting diode. The size of blue LED die used throughout this work was 15 mil square and the dominated wavelength was 460 nm. For the package process, the organic phosphor was firstly mixed with the epoxy and dipped it into the LED bowl of lead frame. Secondly, the pure epoxy resin was full-filled within the lamp model. For the measurement of spectrum and the C.I.E. value, it was found that the near white weight proportional of the epoxy resin A, B and the organic phosphor were 1 : 1 : 0.1.