Wu Chun-Ya

Hydrothermal synthesis of hexagonal-phase NaYF4: Er, Yb with different shapes for application as photovoltaic up-converters

Hexagonal β-NaYF4 co-doped with Yb3+ and Er3+ is directly synthesized under mild conditions using a hydrothermal method. The variation of the ratio of Ln3+ to F− and ethylenediaminetetraacetic acid (EDTA) causes the shape of the microcrystal to change from microplate to microcolumn. The NaYF4 powder is mixed with polydimethylsiloxane (PDMS) to create an up-converter for thin film amorphous silicon solar cells so as to evaluate the effectiveness of the synthesized material as an up-converter. In order to overcome the difficulty in measuring the effectiveness of up-conversion material, a new method of using near infrared illumination to measure the short circuit current densities of solar cells both with and without up-converters is developed. An up-converter with pure hexagonal NaYF4:Yb3+/Er3+ microcrystal produces a high current output. Emission intensity data obtained by photoluminescence suggest that pure hexagonal NaYF4:Yb3+/Er3+ microcrystals are more efficient than nanocrystals when used as up-converting phosphors.

Tricolor microcavity OLEDs based on P-nc-Si:H films as the complex anodes

A P + -nc-Si:H film (boron-doped nc-Si:H thin film) was used as a complex anode of an OLED. As an ideal candidate for the composite anode, the P + -nc-Si:H thin film has a good conductivity with a high work function (∼ 5.7 eV) and outstanding optical properties of high reflectivity, transmission, and a very low absorption. As a result, the combination of the relatively high reflectivity of a P + -nc-Si:H film/ITO complex anode with the very high reflectivity of an Al cathode could form a micro-cavity structure with a certain Q to improve the efficiency of the OLED fabricated on it. An RGB pixel generated by microcavity OLEDs is beneficial for both the reduction of the light loss and the improvement of the color purity and the efficiency. The small molecule Alq would be useful for the emitting light layer (EML) of the MOLED, and the P + -nc-Si film would be used as a complex anode of the MOLED, whose configuration can be constructed as Glass/LTO/P + -nc-Si:H/ITO/MoO3/NPB/Alq/LiF/Al. By adjusting the thickness of the organic layer NPB/Alq, the optical length of the microcavity and the REB colors of the device can be obtained. The peak wavelengths of an OLED are located at 486, 550, and 608 nm, respectively. The CIE coordinates are (0.21, 0.45), (0.33, 0.63), and (0.54, 0.54), and the full widths at half maximum (FWHM) are 35, 32, and 39 nm for red, green, and blue, respectively.

Design for SOP AMOLED display panel

A novel full color SOP (system on panel) AMOLED display based on the MIUC polycrystalline silicon TFT technique, and a new control circuit for the panel, which can deal with both VGA and DVI input signals have been developed. To realize gray-scale a sub-frame technique has been designed and implemented by FPGA device, in which an I2C module has been inserted. Through actual circuit, the whole design has been proven and the advantages of the SOP AMOLED display panel have been confirmed.

Dynamic Ni gettered by PSG from S-MIC poly-Si and its TFTs

A dynamic phosphor-silicate glass (PSG) gettering method is proposed in which the processes of the gettering of Ni by PSG and the crystallizing of α-Si into poly-Si by Ni take place simultaneously. The effects of PSG gettering process on the performances of solution-based metal induced crystallized (S-MIC) poly-Si materials and their thin film transistors (TFTs) are discussed. The crystallization rate is much reduced due to the fact that the Ni as a medium source of crystallization is extracted by the PSG during crystallization at the same time. The boundary between two neighbouring grains in S-MIC poly-Si with PSG looks blurrier than without PSG. Compared with the TFTs made from S-MIC poly-Si without PSG gettering, the TFTs made with PSG gettering has a reduced gate induced leakage current.