Study Of Silicate Phosphor For Wavelength Conversion Based On Enhancing The Efficiency Of Solar Cells

With its rapid development of economy, the steadily increased energyconsumption results in the short of energy supply. It is urgent to search for renewableenergy. Solar Energy has a character of green, safe, pollution-free and Inexhaustible.Solar cell, a direct way to use solar energy, has arising much attention. It has beenwidely used in many fields such as aeronautic and electrical equipments. At present,the photoelectric conversion efficiency of solar cell is relatively low for its narrowabsorption band. It fails to effectively absorb the high frequency ultraviolet light andlow frequency infrared light. Ultraviolet light and infrared light which accountedabout3percent and53percent of sunlight can’t be effectively absorbed by solar cell.If these energys could be used in solar cell, it will play a great role in increasing theefficiency. A simple and practical way is to coating light conversion materials to thesolar cell. These materials can convert the sunlight that can’t be absorbed by cells intothe available light. It includes high frequency ultraviolet light conversion and lowfrequency infrared conversion, i.e. downconversion and uponversion.Firstly, Zn₂SiO₄:Yb³⁺, Er³⁺phosphors, prepared by microwave method, canconvert the infrared light to red and green light. In order to enhance the emissionintensity, Li⁺and Bi³⁺ions are introduced to Zn₂SiO₄:Yb³⁺, Er³⁺phosphors. Theintroduced Li⁺ions makes the upconversion green light intensity increased by sixtimes and the red one increased by three times，respectively. Proper amount of Bi³⁺ions makes both of the red and green emission intensities increased by20times.Spectral probing method with Eu³⁺is used to discuss the reason for the improvement.Secondly, Zn₂SiO₄:Mn²⁺, prepared by solid-state reaction method, can efficientlyabsorb high-energy ultraviolet light and blue light and convert into green light,increasing the photoelectric conversion efficiency. In order to synthesize pure phase ofZn₂SiO₄, the three-step solid state method is used. So as to enhance the luminescentintensity, H₃BO₃and ZnF₂are introduced to the host. The intensity of samples withH₃BO₃can be indeed enhanced here while that with ZnF₂is decreased. In order tofurther improve emission intensity, rare-earth ions Yb²⁺and Tb³⁺are introduced to thehost. It’s found that the emission intensity of Zn₂SiO₄:Mn²⁺is enhanced by the twokinds of ions. Phosphor intensities of Yb²⁺and Tb³⁺codoped samples are increased by2.2and2.8times, respectively. Thirdly, Ca₂ZnSi₂O₇:Eu²⁺phosphors are prepared by solid-state method. It has awide band absorption ranging from ultraviolet light and blue light and then emitsyellow light. So as to increase the emission intensity, fluxes H₃BO₃and CaF₂areintroduced. Both H₃BO₃and CaF₂can enhance the emission intensity ofCa₂ZnSi₂O₇:Eu²⁺, of which CaF₂is better. It makes the emission intensity enhancedby5.34times. In order to further improve the emission intensity of CaF₂dopedCa₂ZnSi₂O₇:Eu²⁺phosphor, a complex composited by NH₄H₂PO₄and Al₂O₃isintroduced. Proper amount of P5+and Al³⁺makes the emission intensity furtherincreased by1.38times. Besides, afterglow is found in Ca₂ZnSi₂O₇:Eu²⁺in theaddition of Dy³⁺. These materials codoped with H₃BO₃and CaF₂have better afterglowperformance.