Study On The Highly Efficient And Stable Perovskite Solar Cells Based On Light Conversion

In recent years,organic-inorganic hybrid perovskite materials with ABX₃structure have become one of the hot spots in the research of optoelectronic materials due to their advantages such as high optical absorption coefficient,long carrier diffusion length,adjustable band gap,simple synthesis method and strong preparative.Perovskite soalr cells?PSCs?are a new type of highly efficient organic-inorganic hybrid solar cells.Compared with traditional silicon-based or dye-sensitized thin-film photovoltaic devices,PSCs have advantages of high efficiency,low cost,flexibility,and simple preparation processes.The photoelectric conversion efficiency of PSCs has increased from 3.8%in 2009 to 25.2%in 2019 in just ten years,and has obtained similar performance to silicon-based photovoltaic devices.Despite the great successes,there are still some challenges.The only way for PSCs to achieve high efficiency and commercial development is to improve the utilization rate of solar spectrum and stability.During the research period,I mainly focused on solving the problems of solar spectrum utilization and stability faced by PSCs.Our results show that efficient and stable PSCs can be achieved by applying fluorescent conversion materials to the interior of the device,utilizing photon energy conversion,and suppressing electron hole recombination.?1?Firstly,we synthesized an efficient Eu-complex Eu?TTA?₂?Phen?MAA and spin-coated it to mesoporous TiO₂,which can be used as the interface modification layer between the mesoporous TiO₂ layer and the perovskite photo absorption layer.After modification,the device efficiency increased from 17.00%to 19.07%.We find that the improvement of device performance can be attributed to on the one hand,Eu?TTA?₂?Phen?MAA can converts incident ultraviolet light into visible light,which is further utilized by perovskite light absorption layer,resulting in more photogenic carriers,on the other hand,due to the reduction of carrier recombination in the device.In addition,the ability of Eu?TTA?₂?Phen?MAA to convert ultraviolet light can improve the problem of poor stability of the device under solar irradiation,and the devices modified by Eu?TTA?₂?Phen?MAA can maintain 86%of the initial efficiency after 100 hours of continuous simulated solar irradiation.This work is of great significance to the study of light stability of PSCs.?2?Secondly,we enhanced NaYF₄:Yb³⁺,Er³⁺@NaYF₄:Yb³⁺,and Nd³⁺UCNPs with gold Au NRs and IR-783 dye as the scaffold layer and introduced them into PSCs to improve device performance by using their efficient up conversion luminescence.Under excitation at 980 nm,the luminescence intensity increased by150 times,and the quantum efficiency increased from 0.2%to 1.2%.Under the synergistic effect of light scattering and up conversion luminescence,the efficiency of the device increased from 19.3%to 20.5%.Under 1.0 W/cm² high power solar irradiation,efficiency of PSCs was further increased from 20.5%to 21.1%.As far as we know,it is currently the most efficient PSCs application based on various up conversion materials.This work shows that the introduction of UCNPs/IR-783dye/Au NRs composite film into PSCs is an effective way to improve PSCs efficiency.?3?Finally,we explored adding Nb⁵⁺to the CsFAMA perovskite precursor solution and applying CsPbBr₃ QDs to the device interior to improve the crystallinity of perovskite films and the humidity and light stability of the device.First,Nb⁵⁺doping enables the efficiency of PSCs devices to reach 20.9%and maintain moisture stability of 85%of the initial efficiency after 1000 hours.The results show that after introducing Nb⁵⁺,the crystallization quality of perovskite films can be improved,grain size can be increased,grain boundary and defect generation can be reduced and electron extraction ability can be improved.In addition,CsPbBr₃ QDs was further applied to the device.By using Nb₂O₅ to isolate CsPbBr₃ QDs from perovskite and an efficient one step spin coating method,the efficiency of the device finally prepared can reach 21.6%,and it has good light stability.In this work,the perovskite photoactive layer was modified and the fluorescence down conversion layer was introduced to provide a simple method for the preparation of efficient and stable PSCs.