Performance Of Photodetectors Based On The Synergistic Effect Of Perovskite MAPbX₃/Organic Semiconductors

Photodetectors have excellent application prospects,especially in high-tech fields such as biomedical sensing,environmental monitoring,optical communication,and space exploration.In practical applications,the photodetector has to face complex application scenarios.In addition,different application scenarios put forward different requirements on the performance parameters of the photodetector.The structure and working mechanism of the photodetectors with a single active material are relatively simple.The spectral response range of the photodetectors is limited by the optical and electrical characteristics of the active material,making it difficult to achieve complex application requirements.The research work in this thesis combines the excellent photoelectric properties of perovskite materials and organic materials to develop the synergistic effect of perovskite/organic materials.Aiming at different application requirements of the photodetectors,the photodetection spectrum range of the perovskite/organic photodetector is adjusted by developing the advantages of perovskite and organic materials in optical and electrical aspects and the flexibility of spin-coating preparation of materials.To provide some viable strategies for the applications of perovskite/organic synergistic photodetectors,we focus on exploring the effect of the transport of charge carriers inside the device overall performance and spectral response range by employing a series of characterization to the films and devices.The main research contents are as follows:1.In order to enhance the performance of the perovskite photodetectors,we introduced a solvent flushing method using dimethyl sulfoxide(DMSO)to optimize the hole transport layer,(poly(3,4-ethylenedioxythiophene):poly(styrenesulfonicacid))(PEDOT:PSS).DMSO-flushing has the following effects:(1)The transmittance of PEDOT:PSS is increased by 10%on average in the range of 380-800nm,which enhances the absorption of perovskite;(2)The crystallinity of the perovskite fabricated on PEDOT:PSS is improved,and the crystal planes are arranged more closely.The average roughness of perovskite film is reduced from 25.07 nm to 10.71 nm;(3)The conductivity of PEDOT:PSS is increased from 2.5×10^-3 m S/cm to 3.3×10^-3m S/cm,which favors for hole collection.The introduction of the DMSO-flushing method has significantly improved the light harvesting,charge carrier transport and extraction of the photodetectors.Based on this optimization,we have fabricated high-performance perovskite photodetectors with a detectivity of 8.77×10¹² Jones and a response time of258 ns under-0.1V bias.2.To achieve the photodetection with a broader response range,we have introduced an organic bulk heterojunction composed of polymer(PM6)and non-fullerene small molecules(Y6)that absorbs in the near-infrared range as a supplementary absorption material for perovskite.The effects of the mixing ratio of donor and acceptor in the organic bulk heterojunction,the thickness of the organic heterojunction and C₆₀ on the performance of the device are investigated.Through searching for organic bulk heterojunctions which are complementary to the absorption of perovskite and matches the energy levels of perovskite,and taking advantage of their synergistic effect,high performance perovskite/organic bulk heterojunction broadband photodetectors are realized.After optimization,photodetectors with the structure of(ITO/PTAA/CH₃NH₃Pb I₃/PM6:Y6(1:1.2?150 nm)/C₆₀(10 nm)/BCP/Ag)can detect the light in ultraviolet-visible-near-infrared spectrum(300-1000 nm).The responsivity and detectivity of photodetectors reached the peak values of 0.52 A/W and 2.86×10¹²Jones at 830 nm,respectively.The response speed and the linear dynamic range of the photodetectors reach 698 ns and 143 d B at 525 nm,respectively.3.To obtain the photodetection with a narrow response,we propose a new strategy by introducing perovskite material as the optical shielding layer of the photodetectors,a planar heterojunction composed of polymer(PTB7)and fullerene small molecules(C₆₀)as the active layer of the photodetectors.A series of narrowband photodetectors without optical filters and the adjustable response has been successfully fabricated.The related mechanism of narrowband photodetection achieved by introducing planar heterojunction is researched.What's more,the effect of the ratio of halogen anion in perovskite and the thickness of perovskite and organic planar heterojunction on the spectrum response of photodetectors is investigated.Finally,a series of narrowband photodetectors with the peak response at 680-710 nm and the full width at half maxima(FWHM)at 50-110 nm are fabricated.The responsivity and detectivity of optimized narrowband photodetectors with the structure of(ITO/PTAA/CH₃NH₃Pb I₃/PM6:Y6(1:1.2?150 nm)/C₆₀(10 nm)/BCP/Ag)reached 0.11 A/W and 1.37×10¹² Jones at 680 nm,respectively.The narrowband photodetectors also have a wide linear dynamic range of 141 d B and a response speed of 4?s.In summary,this thesis consists of applying the synergistic effect of perovskite and organic materials in the photodetectors as an entry point.Employing the solvent modification of functional layer in the photodetectors,the optimization of thickness,the manipulation of the structure of the photodetectors,the transport characteristics and mechanisms of charge carriers in different types of perovskite/organic photodetectors are systematically researched,which provides some ideas for the realization of high-performance photodetectors with various functions such as broadband photodetection and narrowband photodetection.