Study Of Red Conversion Based On Enhancing The Efficiency Of Solar Cells

With the emergence of energy crisis and environmental pollution,solar energy has received considerable attention because it is a green, safe and inexhaustible energy. Solar cells will be widely used in many fields. Photoluminescent materials could covert the sunlight into the responding region of solar cell. Those materials could change the current situation of low efficiency of solar cells, increasing the ulitility of sunlight. In this paper, CaAl₁₂O₁₉:Mn⁴⁺,Ge⁴⁺ which can convert ultraviolet light (UV), violet light and blue light to red light have been prepared by a combustion method. CaAl₁₂O₁₉:Mn⁴⁺,Cr³⁺ which could convert ultraviolet light (UV), violet light, blue light and green light to red light have been prepared by solid-state reaction method accompanying thermal decomposition of nitrate assisted with wet chemical mixing route. LiYF4:Er³⁺,Ho³⁺, a new kind cooperated down and up-conversion material, which can convert blue light, green light and infrared light to red light, have been prepared by a method of co-precipitation.Since most of the solar cells couldn't absorb the ultraviolet, violet and blue light efficiently, we choose CaAl₁₂O₁₉: Mn⁴⁺ phosphor to convert the light of high energy into 657nm red emission. With the introduction of Ge⁴⁺ and the annealing treatment, the red emission intensity in CaAl₁₂O₁₉:Mn⁴⁺ phosphor increases by 81% under 330 nm UVA excitation. The concentration of Ge⁴⁺ and annealing temperature has been optimized in our experiment. And the luminescence mechanism has been discussed.CaAl₁₂O₁₉:Mn⁴⁺,Cr³⁺ which can not only convert ultraviolet violet and blue light to red light, but also convert green light to red light, has been investigated. The concentration of Mn⁴⁺ and Cr³⁺ has optimized in our experiment. And the luminescence mechanism has been also discussed.52% sunlight is in the infrared region. Only a little of infrared light could be absorbed by most of solar cells. At present,upconversion materials can convert the infrared light to the red emission. However, the enhancement of efficiency of electroluminescent is not obvious because of low efficiency of up-conversion. Hence, LiYF4:Er³⁺,Ho³⁺, a new kind material cooperated down and up conversion has been prepared. This material not only converts blue light and green light to red light by stokes shift, but also converts infrared light to red light by up-conversion. What's more, the efficiency of cooperated down and up-conversion is larger than the total of stokes shift and up-conversion, due to the nolinear superposition.