Xiong Shao-Zhen

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.

Research on the boron contamination at the p/i interface of microcrystalline silicon solar cells deposited in a single PECVD chamber

This paper studies boron contamination at the interface between the p and i layers of μc-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary Ion Mass Spectroscopy. It is found that the mixed-phase μc-Si:H materials with 40% crystalline volume fraction is easy to be affected by the residual boron in the reactor. The experimental results showed that a 500-nm thick μc-Si:H covering layer or a 30-seconds of hydrogen plasma treatment can effectively reduce the boron contamination at the p/i interface. However, from viewpoint of cost reduction, the hydrogen plasma treatment is desirable for solar cell manufacture because the substrate is not moved during the hydrogen plasma treatment.

Structural properties of a-SiOx:H films studied by an improved infrared-transmission analysis method

An improved method of fitting point-by-point is proposed to determine the absorption coefficient from infrared (IR) transmittance. With no necessity of empirical correction factors, the absorption coefficient can be accurately determined for the films with thin thicknesses. Based on this method, the structural properties of the hydrogenated amorphous silicon oxide materials (a-SiOx:H) are investigated. The oxygen-concentration-dependent variation of the Si—O—Si and the Si—H related modes in a-SiOx:H materials is discussed in detail.

A 4TH ORDER FULLY INTEGRATED ACTIVE RC COMPLEX FILTER WITH NOVEL AUTOMATIC TUNING SYSTEMS

This letter introduces a 4th order active RC complex filter with 1.5MHz center frequency and 1MHz bandwidth. The total harmonic distortion of the filter is less than −60dB and the image rejection ratio is greater than 60dB. A novel technique is also proposed in this letter to automatically adjust the variation of the time constant. The advantages of the proposed method are its high precision and simplicity. Using 5bits control words, the tuning error is less than ±1.6%.

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.

The mechanism of hydrogen plasma passivation for poly-crystalline silicon thin film

The mechanism of hydrogen plasma passivation for poly-crystalline silicon (poly-Si) thin films is investigated by optical emission spectroscopy (OES) combined with Hall mobility, Raman spectra, absorption coefficient spectra, and so on. It is found that different kinds of hydrogen plasma radicals are responsible for passivating different defects in poly-Si. The H? with lower energy is mainly responsible for passivating the solid phase crystallization (SPC) poly-Si whose crystallization precursor is deposited by plasma-enhanced chemical vapor deposition (PECVD). The H* with higher energy may passivate the defects related to teh Ni impurity around the grain boundaries more effectively. In addition, H? and H? with the highest energy are required to passivate intra-grain defects in the poly-Si crystallized by SPC but whose precursor is deposited by low pressure chemical vapor deposition (LPCVD).

Analysis of heating effect on the process of high deposition rate microcrystalline silicon

A possible heating effect on the process of high deposition rate microcrystalline silicon has been studied. It includes the discharge time-accumulating heating effect, discharge power, inter-electrode distance, and total gas flow rate induced heating effect. It is found that the heating effects mentioned above are in some ways quite similar to and in other ways very different from each other. However, all of them will directly or indirectly cause the increase of the substrate surface temperature during the process of depositing microcrystalline silicon thin films, which will affect the properties of the materials with increasing time. This phenomenon is very serious for the high deposition rate of microcrystalline silicon thin films because of the high input power and the relatively small inter-electrode distance needed. Through analysis of the heating effects occurring in the process of depositing microcrystalline silicon, it is proposed that the discharge power and the heating temperature should be as low as possible, and the total gas flow rate and the inter-electrode distance should be suitable so that device-grade high quality deposition rate microcrystalline silicon thin films can be fabricated.

Reduction of the phosphorus contamination for plasma deposition of p-i-n microcrystalline silicon solar cells in a single chamber

This paper investigates several pretreatment techniques used to reduce the phosphorus contamination between solar cells. They include hydrogen plasma pretreatment, deposition of a p-type doped layer, i-a-Si:H or μc-Si:H covering layer between solar cells. Their effectiveness for the pretreatment is evaluated by means of phosphorus concentration in films, the dark conductivity of p-layer properties and cell performance.

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.

Al-Induced Crystallization of Polycrystalline Silicon Thin Films Based on Solution Method

A new low-cost method to prepare polycrystalline silicon thin films by solution-based aluminum-induced crystallization (AIC) was introduced in this article. Amorphous silicon (a-Si) thin films with 50 nm thickness were deposited by low-pressure chemical vapor deposition (LPCVD) and used as the precursors of crystallization. Aluminate solution with several components was spun on the surface of the a-Si films. Crystallization was accomplished at the annealing temperature between 550 and 620 ℃ for several hours in furnace and N2 ambience. The crystallization effect was dependent on the aluminum concentration in aluminate solution and the surface status of the studied a-Si films. We found that the AIC process could take place only with solution containing meta-aluminates, and continuous polycrystalline silicon thin films could be obtained if the solution concentration was not too low. The natural oxide layers on the surface of a-Si films were good for adhesion of aluminate solution to the films and the formation of larger grains, but would lead to a higher crystallization temperature. In addition, various micrographic patterns taken from the crystallized films were observed, which were resulted from different kinds of Al-salt solution as the source for AIC. In one word, it was important to choose appropriate experiment parameters.