Study On The Luminescence Properties Of Rare Earth Doped NaGdF₄ And Its Application In The Porous Layer Of Perovskite Solar Cells

With the increasing shortage of energy and the demand for clean energy,the development of solar cells has become one of the important tracks for national competition.Rare earth light materials have been applied in the field of solar cells because of their up-conversion luminescence and quantum cutting properties.The good luminescence properties of rare earth luminescent materials are inseparable from good host materials.NaGdF₄is considered to be an ideal host material due to its unique ability to adjust the energy exchange between rare earth impurities.In this paper,NaGdF₄is selected as the luminescent matrix for studying up-conversion and quantum cutting,and applied to the porous layer,aiming to improve the light absorption rate of the perovskite layer.At present,the optimization direction of the perovskite battery is to improve its solar light absorption efficiency.We proposed to mix the porous layer with NaGdF₄:Ho³⁺/Yb³⁺to achieve the above purpose.At the same time,this paper also studied the influence of different water inhibitors on the prepared dense layer and the exploration of the preparation method of the perovskite layer.The samples were characterized by XRD and SEM,aiming to prepare perovskite layers and dense layers with good morphology and high crystallinity.Therefore,we launched the following work:We prepared NaGdF₄:Ho³⁺/Yb³⁺luminescent material by hydrothermal method.Using the 980 laser as the light source,the test shows that the emission wavelength of the sample is located in the green region and the near-infrared region.In order to further improve the up-conversion efficiency,we adjusted the sensitizer Yb³⁺doping concentration and found that the visible light and near-infrared emission peaks were first enhanced and then weakened,and concentration quenching occurred.With the increase of Yb³⁺doping concentration,the luminescence intensity of NaGdF₄:Ho³⁺/Yb³⁺in visible light and near-infrared under the excitation of 448 nm increases first and then decreases.Through lifetime decay calculation,the quantum cutting efficiency of 40%Yb³⁺doping concentration is the best.The quantum transfer efficiency at 541 nm under 448 nm excitation is 79.8%,and the quantum efficiency is179.8%.Considering the strong hydrolysis of butyl titanate,intermediate by-products will be produced in the process of preparing the TiO₂dense layer,so we choose diethanolamine,nitric acid,acetic acid and acetylacetone as water inhibitors.The SEM test results show that the surface of the dense layer prepared with diethanolamine as a water suppressant is free of impurities,and the absorption peak position of the ultraviolet-visible light absorption shows that the absorption peak position is just complementary to the absorption of the perovskite layer,which can reduce the decomposition of the perovskite layer by ultraviolet rays.The perovskite layer was prepared by one-step method and two-step method,and the samples were analyzed by SEM and XRD.The two-step method prepared the methylamine lead iodide with dense structure and better crystallinity.We combined the perovskite layer with the porous layer doped with luminescent materials,and found that the increase of luminescent materials enhances the luminescence of the perovskite layer under excitation at 460 nm,which indicates that the increase of luminescent materials causes the perovskite layer to generate more electron-hole pairs.For further verification,we have prepared a complete five-layer structure except for the electrodes for the convenience of fluorescence detection.The luminescence intensity of this structure decreases under excitation at 460 nm,which indicates that the spin coating of the electron and hole transport layer has successfully separated the electron-hole pairs generated by the light-absorbing layer.This also shows the great potential of NaGdF₄:Ho³⁺/Yb³⁺in perovskite solar cells.