Near Infrared Light Excitation Of H-BN Using Optical Frequency Up Conversion Technology

Wide band gap semiconductor materials refer to semiconductor materials with a band gap width of 2.3 eV and above,such as titanium dioxide(TiO₂),gallium nitride(Ga N),aluminum nitride(AIN)and so on.Because of their unique physical properties,wide band gap semiconductor materials have important applications in lighting,electronic devices,optical storage,photocatalysis and other fields.The wide band gap semiconductor has a large band gap and can absorb light at a shorter wavelength.To achieve its optical excitation,blue light or ultraviolet light with a shorter wavelength is required.Blue and ultraviolet light account for a small proportion of sunlight or cannot reach the ground at all,so researchers began to study the use of near-infrared light to achieve wide band gap semiconductor light excitation.The realization of near-infrared excitation of wide-band gap semiconductor is not only of great significance to improve the existing scientific theory and technology,but also has a wide application prospect in photocatalysis,biological medicine,space exploration and other fields.At present,the reported researches mostly use optical frequency up-conversion technology to achieve near-infrared light excitation of semiconductor materials with a band gap of about 3 eV,such as TiO₂ and Zn O,but have not achieved near-infrared light excitation of ultra-wide band gap semiconductor materials with a band gap of 6.0 eV or above.In addition,most of the reported related studies use the method of preparing core-shell nanocrystals from up-conversion materials and wide-band gap semiconductor materials,and the research on other composite methods needs to be improved.To solve the above problems,we propose a novel structure of photoelectric conversion device with wide band gap semiconductor materials that can be excited by near-infrared light,and on this basis,we use high-order up-conversion micron crystal to realize near-infrared light excitation of ultra-wide band gap semiconductor h-BN.The specific research results are as follows:(1)A device structure based on a wide band gap semiconductor material,a cross finger electrode and an up-conversion micron crystal composite is proposed.The device can be excited by near infrared light and realize photoelectric conversion.It can be divided into 4 layers from top to bottom,which are:special up-conversion micron crystal,cross finger electrode,wide band gap semiconductor material film and sapphire substrate.Using TiO₂ and Ca F₂:Yb as raw materials,a TiO₂ photoelectric conversion device that can be excited by near infrared light was prepared,which realized the near infrared light excitation of TiO₂,and verified the practicality of the device structure.(2)Based on the structure of the photoelectric conversion device mentioned above,using NaYF₄:Yb,Tm,Gd and h-BN as raw materials,the h-BN photoelectric conversion device which can be excited by near infrared light was prepared,and the excitation of h-BN(band gap of 6.0 eV)was realized.The changes of photocurrent during the whole excitation process were explained.In addition,the existence of FRET process is experimentally verified and a schematic diagram of the excitation process is drawn.In this work,near infrared light excitation of ultra-wide band gap semiconductor is realized for the first time.