Studies On P-type Organic Small Molecules/Silicon Heterojunction Photodiode

Compared with the inorganic photodetector, organic small molecules/silicon heterojunction photodiode has the advantages of high responsivity, wide spectral response. This dissertation have prepared silicon-based organic photosensitive diode with three structures, and researched the optoelectronic properties of the devices. Our findings are as follows:I.Preparation and optimization of organic layer and electrode thickness of the organic/silicon heterojunction photodiode based on PTCDA/p-Si have been achieved. Results have shown that the thickness of PTCDA and Au film have a great influence on the light responsivity of the photodiode. The light responsivity can reach the optimal value of0.5A/W in this structure with the thickness of100nm organic layer and20nm electrode.II.Wide spectral response organic/silicon heterojunction photodiode based on PTCDA: CuPc/p-Si has been prepared and their photoelectric performances have been studied. The results show that device achieves high responsivity under405nm,450nm,532nm,655nm and808nm illumination. Both Au/PTCDA:CuPc/p-Si and Al/PTCDA:CuPc/p-Si devices have a maximum light responsivity when light power is0.00396mW under the532nm illumination because of a relatively strong absorbtion at the wavelength of532nm of the PTCDA:CuPc film. Device with Au electrode has the maximum light responsivity of260A/W, while device with Al electrode has a light responsivity only of150A/W, relatively. In addition, device with Al electrode has lower light response at the wavelength of655nm and808nm (light responsivity less than10A/W).Ⅲ. Wide spectrum organic/silicon heterojunction photodiode based on PTCDA:CuPc: PbPc/p-Si has been prepared. Because of a relatively strong absorbtion at the wavelength of450nm of the PTCDA:CuPc:PbPc film, both devices have the greatest light responsivity under the450nm illumination when the light power is0.00258mW. Device with Au electrode has a maximum light responsivity of870A/W, and device with Al electrode only goes to520A/W, accordingly. Under655nm and808nm illumination, the device with Au electrode has a light responsivity more than device with Al electrode. In addition, under the five light irradiation, the organic/silicon heterojunction photodiode has the characteristics of wide spectral response.Ⅳ.A further study of Au/PTCDA:CuPc/p-Si and Au/PTCDA:CuPc:PbPc/p-Si device have found that the blending system of organic film has a great influence on the performance of devices. With0.2mW incident light power, as for Au/PTCDA:CuPc/p-Si, light responsivity goes to20A/W under illumination of532nm with, while Au/PTCDA:CuPc:PbPc/p-Si device reach64A/W under illumination of450nm. Both devices have the characteristics of wide spectral response.