多孔硅-导电聚酯材料复合发光器的光学特性研究

poly-4-dicyanomethylene-4H-cyclopenta2,1-b:3,4-b]dithiophene monolayer(PCDM)是一种导电，低导带聚酯材料。如果在多孔硅纳米结构中附上一层以自组方式生成的PCDM单分子层，就可以制成能够产生稳定电致发光的器件。发光器的结构是金／PCDM／多孔硅／硅／铝，发光器的电致发光，在白天可用肉眼观察到。有很宽的发光波长，几乎覆盖了整个可见光区域且峰值位于650nm，发光器的面积为1cm^2，启动正向电压在14－30V，电流约300mA。经长时间测试，发光器的稳定性很好，在空气中放置3个月，在输入功率不变的情况下，发光强度也不发生变化，当施以反向电压时，样品仍可以发光而且稳定性较高，在250h内I－V未发生明显变化，扫描电镜图像显示PCDM覆盖的表面要比多孔硅表面平整，而PCDM分子有可能进入到多孔硅纳米孔径当中去，起到了提高发光器稳定性和延长其寿命的作用。

Optical Characteristic Studies of Porous Silicon and Conducting Polymer (PCDM) Light Emitting Devices

For obtaining high quality LEDs, many different contacting schemes have been tried, e.g., using metals, conducting polymers and indium tin oxide. The main goal for these is to produce long life, stable and high efficient photoluminescence (PL)/electroluminescence (EL) from porous silicon at room temperature. A conducting polymer is a very promising contact for making high quality LEDs. Porous silicon-based devices produce stable electro-luminescence (EL) by the deposition of PCDM monolayer, a low band gap conducting polymer, into the nano-structure of PS. The structure of these devices is Au/PCDM/PS/Si/Al. The EL emission is bright, visible by the naked eye under normal daylight, and broad in wavelength, covering the whole visible range with a peak at 650 nm. The emission area of the devices is ~1 cm2. The EL starting voltage is in the range of 4~30V and the current is around 300mA. Since preventing oxygen molecules from approaching the PS surface, PCDM films largely increase the time stability of all the devices tested. After exposure to the air for more than 3 months, the PCDM coated samples show nearly the same emission intensity without increase of external power supplied. When a reversing bias is applied, the device can still emit stable light. There is no obvious change inI~Vcurve within 250h. The SEM image shows that the PCDM covered surface is soomther than that of bare porous silicon surface, which may imply that the PCDM may have penetrated into the nano-structure of PS. The substitution PCDM molecules for unstable molecules on the PS surface may results in theincreasing the lifetime and stability of the LEDs.