Research On The Preparation And Properties Of Perovskite Based Photoconversion Devices

Organic-inorganic hybrid lead halide perovskite material has attracted great attention because of its low-cost solution-processable nature and excellent photoelectric properties such as favorable light absorption,high carrier mobility and low exciton binding energy.Perovskite based optoelectronic devices have undergone a decade of rapid development since the Japanese scientist Miyasaka first applied the perovskite semiconductor to the field of solar cell in 2009.However,perovskite based optoelectronic devices still suffer from severe problems such as low efficiency,poor stability and high costs which seriously restrict its commercial development.The determining factors that limit device performance catalysts can be concluded as:?1?low coverage,uneven film formation and small grain size of perovskite absorption layer,?2?energy band mismatch between carrier transport materials and absorption materials,?3?defective electron transport layer?ETL?based on traditional metal oxide materials.The main factors that restrict the device costs are:?1?complex device structure,?2?high energy consumption during the deposition of metal oxide based ETL,?3?expensive organic hole transport materials.Research in this paper is mainly focused on the development of photodiodes,starting from the acquisition of a high-quality perovskite layer,continuing with the optimization of the auxiliary materials and device structure,and concluding with the completion of the integrated system.The details are provided below.?1?Developing preparation techniques of high-quality perovskite.The formation process of perovskite film based on different techniques and substrates is studied with several material characterizations such as UV-vis absorption spectrum,X-ray diffraction spectrum and scanning electron microscope.The crystallization process of perovskite is controlled by solvent engineering.Anti-solvent strategy and Oswald maturation mechanism are applied.By optimizing the reaction time between methylamine halide?IPA solution?and the lead halide precursor,the number of nucleating centers is reduced,and the crystallization rate is increased.The coarsening process is promoted and leads to perovskite with high quality.High quality film deposition on planar rigid substrate,planar flexible substrate and wire-shape substrate is achieved.All perovskite film show uniform,dense and pin-hole free morphology with grain size of over micrometers.Such results lay the foundation for the subsequent device development.?2?Structure optimization of perovskite-based photodiode.For perovskite solar cells?PSCs?,using transparent conductive antimony doped tin oxide?ATO?nanorods as a mesoporous scaffold can reduce the carrier transmission resistance and effectively improve the power conversion efficiency?PCE?.The ATO based PSCs have a PCE of over 20%without hysteresis.For a perovskite photodetector,the composite structure of Cu-Cu₂O-CuO is grown on the Cu wire in situ.The one-step construction of an electrode-electron barrier layer-hole transport layer is realized.Such perovskite photodetector with twisted pair construction has a remarkable detectivity of 10¹³ Jones.?3?Structure simplification of perovskite-based photodiode.Commercial FTO substrate itself is used as the tin source to form an SnO₂ ETL by oxygen plasma treatment.A low-temperature and no-waste discharge ETL fabrication technology is successfully demonstrated with no performance sacrifice.The graded Pb/Sn perovskite absorber is further constructed which has the capability of carrier separation by itself.As a result,the homogeneous junction light absorber has little dependence on CTL.With this absorber,a PCE of 10%can be achieved without any CTL.?4?The integration system construction based on perovskite photodiode.By co-doping perovskite with cesium and bromide,an absorber suitable for artificial light sources is obtained.An ETL based on niobium doped titanium oxide is developed to adapt such an absorber.After systematic composition and energy band engineering,PSCs with a record PCE of 36%are achieved under LED illumination.Through integration with a management chip and energy storage system,an energy self-supply system is realized for practical applications such as calculators,digital clocks and environment monitoring devices.The absorption edge of perovskite can evolve from the ultraviolet to near infrared range by composition manipulating.Using such particular characteristic,by annealing chlorine-based perovskite films in the atmosphere of methylamine iodine,horizontal-graded perovskite films with the absorption edges over the whole visible region are obtained.A device array is constructed on the horizontal gradient layer.A color sensitive photodetector with nanosecond response speed is achieved.It also can serve as a spectrometer with a resolution of about 80 nm.