Research On The Dynamic Processes Of Organic And Perovskite Materials At Excited States

Organic and perovskites have great potential in photovoltaic,light-emitting device,detector and other photoelectric application with excellent photoelectric properties.However,organic and perovskite are still far from practical applications.Here,using a comprehensive research method of magneto-optical-electricity to expand the research on the basic dynamic process of organic and perovskite at excited states,providing new design idea for material synthesis and device construction.（1）The interfacial transport layer is important for elaborating organic photovoltaic efficiency.Despite some fundamental knowledge regarding their electrical and optical properties,a full realization of their impact on photo-active layers is still lacking.Here,a new insight into the impact of the interfacial transport layers on physical properties of OBHJ[ITO/PEDOT:PSS/PIDTDTQx:PC₇₀BM/PFN/Al].Multiple measurements were performed at steady states aiming to understand the role of interfacial transport layer in OBHJ.Experimental results validated the assumption that optoelectronic properties of the BHJ(PIDTDTQx:PC₇₀BM),can be influenced due to the presence of the electron/hole transport layers.This issue was examined by the interfacial trap-related DOS,₀（88）（7）,₀（88）（7）,,photo-induced electrical polarization,energetic disorder and magneto-photocurrent.This concept guide people to reconsider the critical role of the interfacial transport layer in OBHJ,to compensate with two controversial assumptions,（i）properties of the BHJ is nearly unaltered due to the presence of the interfacial transport layers.（ii）they facilitate the charge carrier extraction and injection.（2）Non-fullerene（NF）molecules have exhibited prominent optoelectronic properties in OBHJ.Although the highly efficient exciton dissociation can happen with a smaller driving force,the underlying energy loss including exciton dissociation and electron-hole recombination in the NF acceptor remains unclear.Essentially,energetic disorder characteristic is a common feature in organic semiconductors as well as their organic blends due to the molecular random distribution and the D:A interpenetration network.Owing to their different molecular structures in contrast to the bulky-ball shaped fullerene-derivative counterpart such as PCBM,a comprehensive understanding for the trap associated energetic disorder characteristic and distribution are merits to further eliminate the V_oc loss.Here,a highly efficient organic BHJ solar cell comprising ITO/Zn O/PBDB-T:ITIC/Mo O₃/Al was fabricated.The PBDB-T and NF ITIC form an interpenetrating network.With the impedance spectroscopic technique,surface and bulk trap states can be revealed.Moreover,both of them respectively contain deep and shallow traps with different energetic locations in energy gap.The results help to explain the appearance of double and triple C-V bands.With pump-probe laser spectroscopic measurements,the trap states may locate far below the photo-absorption band-edge.This work serves an insightful view on the trap states in the NF based OBHJ and is valuable for minimizing the energy loss.（3）Optically exciting the gap states can lead to multi-photon infrared-to-visible up-conversion（UC）PL in quasi-2D perovskite(（PEA）₂（MA）₄Pb₅Br₁₆)films under CW 980nm laser excitation at room temperature.The quadratic dependence between excitation and emission intensities indicates that UCPL results from a two-photon（2P）excitation process.When the gap states are decreased by reducing the n value in the RPP nanoplates,the 2P UCPL becomes negligible in 2D perovskite films when the n<3.This confirms that the gap states are indeed responsible for generating the 2P UCPL.Furthermore,2D perovskite films are formed with the uniform dispersion of different-n-value nanoplates through anti-solvent processing to generate gap states and 2P UCPL.The uniform dispersion of different-n-value nanoplates was confirmed in 2D perovskite films by mechanically scratching-off multiple monolayers.Moreover,the 2P UCPL is sensitive to the magnetic field,leading to a magneto-PL upon optically exciting the gap states.This observation indicates that the gap states are formed as spatially extended states in larger-n-value nanoplates.Furthermore,polarization-dependent PL studies show that the gap states experience orbit-orbit interaction to develop into spatially extended states.Clearly,the gap states functioning as spatially extended states through orbit-orbit interaction allow the multi-photon absorption to generate 2P UPPL in 2D perovskite films.