Halogen Ion Pair Enhances The Photoelectric Performance And Stability Of Perovskite Battery

Organic-inorganic lead halide perovskite has been widely used in solar cells and other photoelectric semiconductor devices due to its excellent photoelectric properties and low cost solution manufacturing.In organic-inorganic perovskite solar cells(PSCs),the interface between the carrier transport material and the perovskite film plays an important role in the device performance.At present,the photoelectric conversion efficiency of PSCs has been exceeded to 23%.But in the outdoor environment,due to humidity,light,temperature,oxygen and other factors,the stability of the device is very poor and the service life is very short.This is also an obstacle to the industrialization of PSCs,so it is of great importance to study how to solve the stability problem of PSCs.Based on these issue,this paper studies the interface of carrier transport materials and stability of device,and improves the performance and stability of PSCs through interface engineering and additive engineering.The following is our research content:(1)Nanoparticles of nickel oxide with Cl-ions(NiOx-Cl)were synthesized with different size and used as hole transport layer(HTL)in reverse(p-i-n)structured PSCs.Compared with devices of nickel oxide(NiOx)film as HTL,The performance of device with NiOx-Cl HTL is greatly improved,power conversion efficiency(PCE)of the device is increased from 14.3%to 17.44%,In air with a relative humidity(RH)of 40%,the PCE was degraded only by 20%after aging for 12 hours.More importantly,the hysteresis effect almost completely disappeared,and the hysteresis index decreased from 9.0%to 1.7%.(2)The electron transport layer(ETL)of Ti02 was modified by using the multifunctional material lithium fluoride(LiF)to increase its electron mobility from 6.4 10-4 cm2V-1s-1 to 2.87 10-3 cm2V-1s-1(increased by more than three times),thereby increasing the charge transfer efficiency between the FA-based perovskite and the ETL;Moreover,the grain size of the FA-based perovskite was increased from 1 um to 5 um due to the F-ions;The defects of the perovskite film were reduced and the crystallinity was improved;The average PCE of the devices was 19.8%,and the hysteresis index was reduced from 7.7%to 2.0%.Since the TiO2/LiF film reduces the transmittance of ultraviolet(UV)light,the UV light stability of the optimized device is improved by 1.6 times compared with the device without LiF.After UV illumination of 12 hours,the PCE of device with LiF was degraded only by 22%.(3)We prevented the formation of the 5-phase and stabilized the a-phase in the FA-based perovskite by adding an inorganic small molecule niobium pentafluoride(NbF5)to the perovskite precursor solution.As a result,the hysteresis effect of the PSCs with NbF5 has been weakened,the hysteresis index was reduced from 12.0%to 6.0%,and the PCE of the devices was over 20%.More importantly,the PSCs with NbF5 additive exhibit an improved air stability by 10-fold,retaining nearly 80%of their initial efficiency after aging in air for 50 days.In addition,under illumination of Xenon lamp(100 mW/cm2,AM 1.5 G)without any UV filter,the stability of the PSCs with NbF5 additive was improved 5-fold compared with the control devices without NbF5.Thus,this work has presented a novel and promising route to improve the photovoltaic performance and phase stable of FA-based PSCs.