Preparation Of TiO₂ Electron Transport Layer Based On Low Temperature And NiO Interface Modified Perovskite Solar Cells

Perovskite solar cells have attracted a great deal of attention due to their rapidly increasing energy conversion efficiency from 3.8%to a maximum of over 22%in just a few years.The organic-inorganic lead halide perovskite has excellent properties such as high extinction coefficient,wide light absorption range,low exciton binding energy,long carrier lifetime and diffusion length,making it an excellent material for the third generation of solar cells.For perovskite solar cells,how to improve the energy conversion efficiency and reduce the manufacturing cost are the key issues in its development.Due to the continuous development of the perovskite method,the perovskite thin film growth process is gradually improved,To further improve the performance of perovskite batteries,the dynamics of carriers in all layers of the device must be strictly controlled.In this paper,we start from two different ideas.The traditional preparation of dense TiO₂ layer is often achieved by high-temperature sintering.In this experiment,NOBF₄ was used to exchange the oleic acid and oleylamine ligands in TiO₂ for ligand exchange to achieve the process of preparing perovskite solar cells at low temperature,which reduced the cost of battery preparation to a certain extent.On the basis of low temperature,the interface between layers of perovskite cells was further modified to improve the efficiency of perovskite cells.The specific research contents are as follows:?1?Based on the laboratory preparation of TiO₂,TiO₂ is coordinated with oleic acid and oleylamine long hydrocarbon molecules to make them disperse better in non-polar hydrophobic solvents.However,the existence of such an insulating ligand limits the formation of TiO₂ electrons transport layer of low temperature preparation.In this experiment,a simple ligand exchange of oleic acid oleyl amine ligand in TiO₂solution was carried out by using NOBF₄.It was found that NOBF₄ could completely peel off the insulating ligands on TiO₂ surface.Compared with the traditional high temperature sintering at 500?,the TiO₂ after the ligand exchange can obtain the high quality electron transport layer thin film only under the treatment of 150?.The perovskitesolarcellswiththeplanarstructureof FTO/TiO₂/Perovskite/Spiro-OMeTAD/Au prepared by TiO₂ thin films assembled at the optimal concentration achieved an average efficiency of 17.28±0.73%and an optimum efficiency of 18.51%.Compared with the low-temperature preparation of TiO₂-based battery device that has not been ligand-exchanged,the high-temperature calcination process is avoided and the better optoelectronic properties are exhibited.?2?In perovskite solar cells,the interface between the layers and the interface between the layers and the interface between the perovskite grains and the grains have a significant impact on the performance of the battery.Interface modification has now proved to be one of the most effective ways to improve battery performance.On the basis of low temperature,we modified the TiO₂ electron transport layer with NiO after ligand exchange to prepare a perovskite solar cell with a planar structure of FTO/NiO@TiO₂/Perovskite/Spiro-OMeTAD/Au.The influence of the presence of NiO on the crystallinity of perovskite was studied,and the effect of NiO on the optoelectronic properties of perovskite cells was also studied.The experiment found that a NiO thin layer with a concentration of 1 mg·ml^-1 can promote perovskite crystallization and reduce carrier recombination,resulting in a proper increase in current density.The average efficiency of the prepared battery module reached 18.22±0.55%,the best efficiency increased to 19.42%.?3?In addition to the interface between TiO₂ and perovskite,the interface between the perovskite and Spiro-OMeTAD also affects cell performance.It has been pointed out that the doped Spiro-OMeTAD reacts with free I ions in perovskites,resulting in a decrease in hole transport capacity.We use NiO solution coated on the perovskite layer,through the introduction of a modified layer,to avoid the perovskite layer and Spiro-OMeTAD direct contact,and a perovskite solar cell with a planar structureofFTO/TiO₂/Perovskite/NiO/Spiro-OMeTAD/Auwasprepared.Experimental studies have shown that a thin layer of NiO above the perovskite can promote interfacial contact between the perovskite layer and the hole transport layer and reduce the voltage loss at the interface.Finally,the average efficiency of the prepared perovskite solar cell device was 18.43±0.57%,the best efficiency was19.72%,and the high voltage of 1.16 V was obtained.