The Research On Photogenerated Charge Transfer Of Organic/inorganic Heterojunction

The behavior of surface photogenerated charge transfer in organic/inorganic heterojunction is the basic behavior in photo-electric conversion, photocatalysis and molecular-electric device. Surface Photovoltage Spectra (SPS) is a sensitive tool for detecting the photogenerated charge at the surface of semiconductor materials, which makes it the most important measuremant for studying the behavior of photognerated charge transfer at the surface and interface of semiconductor materials. Applied external electric field can promote the separation of photogenerated electron-hole pairs, thus influence the transfer, capture and recombination of photogenerated carriers. So, field induced surface photovoltage spectra (FISPS) based on the basic of field effect which is normally considered as the steady state SPS can detect the nice change of photogenerated charge at the surface of semiconductor materials. In this thesis, we built the photovoltage electric field scanning (PVEFS) technique based on the SPS and FISPS. This measurement focuses on the photogenerated charge transfer, capture and recombination on the semiconductor materials. Therefore, we developed the basic theory of surface photovoltage and introduced the electric field induced dipole model for the first time. We also built the method for interpretting nanoparticles and nano-cmoplexs which is significantly useful for comprehending the behavior of photogenerated chrage transfer. I. We pointed out that the semiconducor nanoparticles anisomerously bind up the photogenerated charge and determined the state of free exction and bound exction after the resrarch on the TiO2 nanoparticles in chapter II. We have also discussed the photovoltaic characteristic at the interface of anatase and rutile, and introduced the conception of the photovoltage reverse. Based on the determination of free exction and bound exction, we introduced the electric field induced dipole model and pointed out that the built-in field is the significantly driving force which affects the photovoltage. Based on the comprehension of chapter II, we have disscussed the factors such as conductivity, particle size and absorbed substance which make the traditional theory of photovoltage including the solid energy band theory is not suitable for interpretting the behavior of photogenerated charge transfer in nano semiconductor materials in chapter V. Based on the field induced dipole mechanism, we built the photovoltage electric field scanning (PVEFS) technique. Through the analysis of obtained curves, we found that it almost suits all of our smaple. II. Chapter III and IV is mainly focus on studying the porphyrin/TiO2 and liquid crystal/TiO2 system. We have studied the photovoltaic properties of porphyrin/TiO2 system in chapter III. We found some factors that affect the photovoltage of porphyrin: 1. The size of TiO2, 2. Category of functional group of porphyrin. 3. The amount of functional group of porphyrin. The conclusion is as follows: 1. The TiO2 with small size facilitate the separation of photogenerated electron-hole pairs. 2. The category of the functional group of porphyrin significantly affect the photovoltage of system, the electron donating group makes porphyrin easily contact with TiO2, while the electron withdraw group makes this difficulty. 3. The amount of functional group also affect the generation of photovoltage. At the same time, the testing results in chapter III are also useful for introducing the dipole theory in chapter V. Chapter IV studied the photovoltage characteristic of liquid crystal/TiO2 system. The results show that photovoltage correlates not only with the mentioned factors in chapter III, but also with the steric hindrance effect. Porphyrin with evident...