Application Of Tin Oxide Films Prepared By Atomic Layer Deposition In Perovskite Solar Cells And Photoelectronic Detectors

Perovskite photoelectric conversion device has been a hot research topic since its birth.Among them,perovskite solar cells are considered as one of the next generation commercial photovoltaic cells,their power conversion efficiencies have increased from 3.8%to 25.7%in,which have exceeded most solar cells.However,the stability problems such as easily degraded induced by water and oxygen,ion migration during its operation,will reduce the performance of the solar cell,which restricts its further commercial development.To solve this problem,researchers introduced a buffer layer into the battery structure.The use of buffer layer can block holes,isolate water and oxygen,and reduce the interfacial energy level barrier and effectively improve the stability of devices.Currently,most of the buffer layers used are organic materials.However,organic materials have problems such as poor properties of blocking water and oxygen,bad thermal stability,which further aggravate the performance attenuation of battery devices.Inorganic oxides can be used as good interfacial charge transport materials because of their high physical and chemical stability and good charge transport performance.Among them,SnO_x（x=1-2）thin films have advantages of convenient preparation process and good optoelectronic performance.SnO_x thin films are widely used in the fields of solar energy batteries and photodetectors.Meanwhile,Atomic Layer Deposition（ALD）technology is very popular in the field of thin film deposition It can accurately control thin film thickness at the atomic layer scale.It has the advantages of small substrate damage,high depth ratio and high film quality.It has great application potential in the field of semiconductor film deposition.To solve the above problems,we take advantage of ALD technology to prepare high-quality SnO_x film（20 nm）and substitute the use of organic materials as the buffer layer of trans-perovskite solar cells.Using SnO_x films with better transmittance and higher electron mobility as the buffer layer is beneficial to improve the device performance.The prepared SnO_x films have better hydrophobicity,which can improve the stability of the device in water-oxygen-rich environment.Meanwhile,the preparation of SnO_x using ALD technology allows for precise control of films thickness and better surface coverage of the prepared films.We first studied the effects of deposition temperature on films growth rate,surface morphology and photoelectrical properties of SnO_x films prepared by ALD.We found that high quality SnO_x films can be prepared at 110℃,which shown lower surface roughness and better electrical properties.However,the preparation process of SnO_x films by ALD will use high-pure-water as oxygen source,too much water will degrade device performance.Then,the effects of different water pulse times on photoelectric properties of SnO_x films and the solar cell prepared with SnO_x as buffer layer were studied.We found that,when the water source pulse time increased gradually between 0.06 s-0.1 s,the performance of the prepared device was the best.If the pulse time of water source is too short,the quality of the film will be reduced.If the pulse time of water source is too long,the device will be damaged and the device performance will be reduced.Moreover,the gradually increase of water source pulse time can realize the gradient change of SnO_xfilm band gap and achieve better energy level matching of the device.Finally,the optimized SnO_x buffer layer improved the open-circuit voltage（1.16 V）,short-circuit current density（23.2 mA/cm²）and power conversion efficiency（21.7%）of the solar cell.Perovskite single crystal photodetectors are also the current research hotspots.However,current researches mainly focus on the development of new active layers,and less research has been done on the impact of electron transport materials on detectors performance.Meanwhile,there are lots of defects on the surface of the untreated FAPbBr₃ single crystal,which will degrade the device performance.To solve the above problem,a layer of SnO_x thin film was prepared on the surface of FAPbBr₃perovskite single crystal,using tetrakis（dimethylamino）tin（TDMASn）as tin source precursor and ozone（O₃）as oxygen source precursor by ALD technology.Then,FAPbBr₃ perovskite single crystal photodetector was fabricated.We investigate the passivation effect of O₃ on the surface of FAPbBr₃ single crystals and the influence of SnO_x thin films on the photodetection performance of FAPbBr₃ perovskite single crystal photodetectors.We found that using O₃ as ALD oxygen source precursor can effectively passivate the surface defects of FAPbBr₃ perovskite single crystals and reduce the charge recombination rate on the single crystal surface.Meanwhile,Using SnO_x thin films prepared by ALD technology as electron transport layers can improve the carrier extraction ability of detectors a.The detectors prepared by this way obtain a low noise current of 3.1×10^-13 A Hz^-1/2.