Interfacial Passivation Suppressing Defects To Enhance Photovoltaic Performance Of Perovskite Solar Cells

Developing solar cells and improving the rate of using solar energy solar energy is an important way for human to overcome the energy crisis and protect the ecological environment of the globe.In recent years,as a new generation of photovoltaic technology,perovskite solar cells（PSCs）have been rapidly advanced,promising to change the situation that solar cell technology is expensive and inadequate.However,PSCs still face the problems of low efficiency and poor stability under the condition of large-area preparation.Defects in perovskite usually lead to non-radiative recombination of carriers and accelerate perovskite phase decomposition,which negatively affects the efficiency and stability of PSCs.Therefore,the passivation of surface and buried interface of perovskite by post treatment and dopant predeposition were studied in this paper,aiming at defects located frequently at the interface of perovskite.The efficiency and stability of PSCs were improved by interface passivation.Using Lewis base or ammonium halide to passivate the surface defects of perovskite is an effective strategy to suppress the non-radiative recombination of perovskite carriers.In this work,the surface defects of perovskite were passivated by using Piperazinium Iodide（PI）via post treatment.X-ray Diffraction（XRD）and Scanning Electron Microscopy（SEM）showed that the passivation strategy improved the crystallinity and crystal quality of perovskite.Ultraviolet-visible Spectrophotometry（UV-Vis）showed that the absorption edge of perovskite were slightly redshifted after passivation.The results of X-ray Photoelectron Spectroscopy（XPS）confirmed that PI can passivate the defects caused by the uncoordinated"Pb"through the interaction between"N"atom and"Pb"suspended at the surface of perovskite.Photoluminescence Spectroscopy（PL）and Time-resolved Photoluminescence Spectroscopy（TRPL）showed that PI effectively surppress the non-radiative recombination and increased the carrier lifetime of perovskite.Furthermore,the inverted planar perovskite solar cells were fabricated to investigate the passivation effect.The results showed that the post treatment with PI boosted that Voc,Jsc,FF,PCE of PSCs from 1.041 V,21.29 m A/cm²,74.09%and 16.41%to 1.125 V,22.15 m A/cm²,76.27%and 19.02%,respectively;The performance results of unencapsulated devices during the storage period of 50 days show that the stability of PSCs with PI post-treatment is better than without.The improvement of performance and stability for PSCs with post-treatment is mainly attributed to the reduction of surface defects of perovskite which effectively surppress the non-radiative recombination of carriers.At present,research on passivation of surface defects of perovskite is relatively mature,while there is relatively little research on passivation of the buried interface of perovskite.In this work,the perovskite buried interface was passivated by pre-spinning coating deposition of Benzene-amine molecules,including Aniline（A）,Benzoylamine（BA）,Phenethylamine（PEA）and3-Phenyl-1-propylamine（3-PH-PA）,before deposition of perovskite film.Fourier transform infrared spectroscopy（FTIR）showed that the"N"atom on the amino group of Benzene-amine molecules could coordinate with"Pb",passivating the defects caused by the unsaturated"Pb".XRD and SEM showed that the passivation of perovskite buried-interface by A,BA and PEA can improve the crystallinity and grain size of perovskite,and decreases Pb I₂ in perovskite;While3-PH-PA induces a large amount of Pb I₂ in perovskite,it is speculated that the interaction between Benzene-amine molecule and perovskite is related to the length of its alkyl chain PL and TRPL spectra showed that the passivation of perovskite buried interface by A,BA and PEA molecules effectively improved the charge transfer rate between perovskite and hole-transport layer Ni O_x.Space-charge-limited-current（SCLC）method proved that the passivation of perovskite by Benzene-amine molecules reduced the defect concentration of buried interface of perovskite.Finally,the PCE of PSCs based on perovskite buried-interface passivated by A,BA,PEA and3-PH-PA increased from 16.41%to 18.64%,18.68%,19.61%and 17.92%,respectively.At the same time,the stability of the device is improved after passivation.This simple and effective passivation strategy can be applied to the preparation of large-scale perovskite solar cells in the future.