Ultrafast Study On Photoinduced Charge Transfer Mechanism Of Photoelectric Materials

With the rapid increase of population,the traditional fossil energy consumption caused serious impact on the environment.Finding the suitable alternative energy become significant and is one of the urgent problems today.At the end of the 20th century and the 21st century,most of local war was taken place to grab more oil resources.The development and utilization of renewable solar energy can reduce even get rid of the dependence of traditional fossil energy.The surface plasmon character of noble metals are derived from the interaction of electromagnetic waves and conduction electrons in the metal,which can greatly improve the photoelectric response of the device.Gold nanoparticles as a stable precious metal nanoparticle have received more and more attention in recent years,mainly because they have many attractive properties,such as simple preparation and easy functionalization.At the same time,it has a strong ability to absorb visible light due to its surface plasmon effect.Gold nanoparticles can be widely used in many applications,such as in materials science applications,multiple types of functional assembly;size-related electrical,magnetic and optical properties?quantum size effects?,and their applications in photocatalysis and biology.The research on the surface plasmon effect of gold nanoparticle is a hot topic in the field of new materials and energy science research.Exploring visible light responsive materials that make full use of sunlight is the key to improving the performance of photoelectric conversion materials.Applying the surface plasmon effect of gold nanoparticles to photoelectric conversion will greatly improve the visible light absorption performance and light stability of conventional photoelectric conversion materials.We know that solar cells based on bipyridylium hydride derivatives/titanium dioxide nanocrystalline composite films are currently inexpensive,highly efficient and practical.But the biggest problem is the stability of the dye.As a stable metal material,gold nanoparticles can be used to replace this traditional photosensitizer to solve this problem.The femtosecond ultrafast spectroscopy provides a very sensitive experimental method for studying charge transfer behavior.Using ultrashort laser pulses as a tools of excitation and detection of excited state,transient processes on atoms and molecules can be studied by measuring transient absorption spectra and kinetics.In the current research,how surface plasma of the noble metal affect the efficiency of photovoltaic devices was be explained by measuring the value of the photoelectric conversion efficiency.The key debate is the explanation of mechanism that the enhancement of the photoelectric conversion efficiency is caused by the charge transfer of the thermal motion of the electron or electron injection from the noble metal to the corresponding receptor upon excitation of surface plasmon band of the noble metal.It is of great practical significance to clarify this mechanism by using ultrafast spectroscopy.In this paper,we use chloroauric acid as a raw material and polyvinylpyrrolidone as a protective agent to synthesize gold nanoparticles of different diameters by increasing the molar content of gold particles in the drug.The gold nanoparticles are then assembled with titanium dioxide?TiO₂?,and films having a thickness of about 15?m are prepared by doctor blade method.The mechanism will be clarified by studying the charge transfer process of different size gold nanoparticles assembled with semiconductor systems upon excitation of surface plasmon band using femtosecond transient absorption kinetics.