Preparation And Optoelectronic Performance Of Perovskite Solar Cells Based On NiO Inorganic Hole Transport Layer

The research and application of renewable energy will contribute to ameliorate the energy crisis and environmental pollution in the world.Among all the renewable energy sources,solar energy has been considered as one of the most potential energy sources,and an important way to use the solar energy is employing solar cells for the conversion of solar energy into electric energy.Recently,organic-inorganichybridperovskitematerials(ABX₃,A=CH₃NH₃⁺（MA⁺）,NH=CHNH₃⁺（FA⁺）;B=Pb²⁺,X=Cl^-,Br^-,I^-)have attracted extremely research attention owing to their strong light-absorption,long charge carrier lifetimes,high carrier mobility,long carrier diffusion length and easy processing,and more and more researchers have focused on the development of these materials-based perovskite solar cells（PSCs）.Particularly,inverted PSCs have been received considerable attention due to its simple fabrication process.Despite numerous hole transport materials（HTM）reported in inverted PSCs,nickel oxide（NiO）has been emerging as one of the most promising inorganic HTM in planar PSCs because of its good environmental stability,low cost,large bandgap and good energy level alignment with perovskite layers.However,as an inorganic HTM,the poor carrier mobility of NiO film is an urgent problem to be solved.Till now,element doping has been conceived as one of the most effective way to improve it.In this thesis,NiO thin films were prepared by the magnetron sputtering or sol-gel process,and the influence of process parameters on the performance of NiO thin films was investigated.Meanwhile,the sol-gel-processed NiO thin films were doped by yttrium,and the performance of the yttrium-doped NiO thin films were also studied.In addition,the above-obtained NiO thin films were empolyed for inverted PSCs,and their corresponding optoelectronic performance were further investigated.Main contents are listed as follows:1.Preparation and characterizations of PSCs based on magnetron sputtering NiO thin films inorganic hole transport layerNiO thin films（20-NiO,150-NiO and 300-NiO）were prepared through magnetron sputtering process under different substrate temperatures（20oC,150oC and 300oC）,and the influence of the substrate temperature on the properties of NiO thin films as well as the PSCs was also studied.From the results,we can find that with the increase of substrate temperature,the crystallinity of NiO thin films became better in accompany with a larger grain size,thus resulting in a higher power conversion efficiency（PCE）of PSCs.The PSCs based on 300-NiO thin film had the champion PCE of 11.43%,which was increased by about 32%in comparison with that of the 20-NiO thin film-based PSCs.This could be ascribed to the better light transmittance and the higher hole mobility of the 300-NiO thin film,which could promote the optical absorption as well as the separation efficiency of photogenerated charges of perovskite layer thus leading to the enhanced PCE.2.Preparation and characterizations of PSCs based on sol-gel NiO thin films inorganic hole transport layerVarious NiO thin films were prepared using different precursor concentrations（i.e.,0.05 M,0.10 M and 0.15 M）by a sol-gel process at different spin-coating speeds（i.e.,2000 rpm,3000 rpm,4000 rpm and 5000 rpm）.The results show that when the precursor concentration was 0.10 M and the spin-coating speed was 4000rpm,NiO thin film had the minimum surface roughness,suitable thickness and good crystallization.When using this NiO thin film as the HTL,the PSCs exhibited the highest average PCE of about 10.28%.3.Preparation and characterizations of PSCs based on Y-doped NiO thin films inorganic hole transport layerY-doped NiO thin films containing different Y doping concentrations（x=0,3,5,7 and 10）were prepared through sol-gel process for the first time.The transmittance of the NiO thin films was almost not influenced by the Y doping,which could ensure more photons to reach the perovskite layer for photocurrent generation,whereas the hole mobility of Y-doped NiO thin film was increased with the increase of the doping concentration of Y element.Notably,the PSCs using a5%Y-NiO HTL exhibited the best performance with a PCE of 16.31%,resulting in a27.62%enhancement in comparison with the pure NiO-based PSC device,and also showed neglectable hysteresis.The enhanced performance of the 5%Y-NiO-based PSCs could be attributed to the improved hole mobility,the more compact perovskite layer morphology,the more efficient charge extraction from perovskite layer as well as the lower recombination probability of charge carriers.