Study On The Photocarrier Dynamics Of CuS And CuS-P3HT Van Der Waals Heterostructure

As an important p-type semiconductor,CuS has a high hole mobility and a broad application prospects and promotion value in charge storage and other aspects.Despite a considerable number of reports on morphology control,chemical synthesis and device design,there are few reports on the carrier dynamics information of CuS and its van der Waals heterostructures on ultrafast timescales.The study of the carrier injection behavior of materials by ultrafast laser pulses can help us to understand the ultrafast kinetic information of photogenerated carriers in layered materials,which is useful for exploring the underlying reasons for charge transport in matter from the perspective of fundamental physics and the interaction of light and matter.In this paper,the spatiotemporal dynamics of photogenerated carriers in CuS,the effect of pressure regulation on CuS,and the interlayer ultrafast charge transfer process of CuS-P3HT heterojunctions were investigated by micro-transient absorption spectroscopy.The innovation results are as follows:The photogenerated carrier dynamics of CuS were studied by transient absorption spectroscopy in microdomains.Coherent optical phonon and photogenerated carrier-induced transient absorption are observed in CuS.After successfully separating the coherent optical phonon signal from the photogenerated carrier signal,its correspondence with the Raman-active phonon vibrational mode is proved by the time-dependent Fourier transform.Time-resolved measurements of differential reflection signals induced at room temperature reveal that the photogenerated carrier lifetime of CuS is about 1.5 ns;spatially resolved measurements reveal that the photogenerated carrier diffusion coefficient in the CuS plane is about 4.5 cm~2/s.These results provide deep insights into the photogenerated carrier dynamics properties of CuS and contribute to the development of various optoelectronic devices based on CuS.A high-pressure reflectance spectroscopy system was designed and constructed to detect the pressure-induced changes in samples in situ.The electronic structure,phase structure,and carrier dynamics of CuS under different pressures were systematically studied by steady-state absorption spectroscopy,Raman spectroscopy,and transient absorption spectroscopy.Through the study of reflection contrast spectroscopy and Raman spectroscopy under pressure,the blue shift of the CuS bandgap and the softening of the Raman mode under pressure regulation were observed,revealing the effective regulation of its electronic structure and phase structure by pressure.The time-resolved microdomain absorption spectroscopy results at room temperature show that the photogenerated carrier dissociation rate of CuS gradually increases with pressure,which has a significant positive effect on the solar photocurrent enhancement.For the first time,the ultrafast interlayer charge transfer and exciton dynamics process between CuS and P3HT as an organic-inorganic van der Waals heterostructure,which is different from those composed of most of the previous layered materials,has been investigated.The difference is that evidence for the involvement of thermal excitons in transport is observed during the charge transfer between their layers.Combined with temperature-changing photoluminescence spectra and transient fluorescence spectra,it is confirmed that CuS is the cause of the fluorescence quenching of P3HT,and there is an obvious electron rather than exciton transfer process between the organic-inorganic layers.The established schematic diagram of charge transfer between layers of P3HT and CuS to form a heterostructure.This information helps to provide a fundamental understanding for the further development of photovoltaic devices related to thermal excitons and electron transport based on organic-inorganic van der Waals heterostructure interfaces.