An experimental detail on the morphology engineering and characterizations of the all-inorganic Sn-based perovskite (here CsSnI3) thin films and their application in photodetectors are presented. In particular, we demonstrated that the chlorobenzene anti-solvent treatment during thin-film spin coating could effectively optimize the morphology properties of the obtained CsSnI3 thin film. SEM and AFM measurements showed the uniform thin film with nanorod-like nanocrystalline morphology. In addition, EDS and XPS measurements confirmed the low level of oxidation of the thin film, indicating good ambient stability. A planar photodetector was also made with the prepared thin film, and electrical characteristics were taken. The dark current and photocurrent were found in the range of 10−9 A and 10−7 A, respectively, with an on/off ratio of 102. The photoresponsivity was 10−5 AW−1. A further experiment was conducted to make composite thin films between CsSnI3 and CNTs for additional morphological engineering. The SEM measurement and Raman mapping manifested the nanonet-like morphology of the composite thin film. The quenching of the photoluminescence curve indicated the efficient photo-generated carrier extraction from the CsSnI3 matrix to CNTs. The absorption spectra also showed enhanced absorption ability of the prepared composite thin film. A hybrid photodetector made from the composite thin film showed dark current and photocurrent in the range of 10−6 A and 10−4 A, respectively, with an on/off ratio of 102. The photoresponsivity was 10−2 AW−1. Due to the combination of the CNTs with CsSnI3, the photoresponsivity increased 1000 times. At the same time, the hysteresis of the hybrid photodetector also reduced significantly compared to the pristine CsSnI3-based photodetector.
optoelectronic devices, including photodetection devices, have been dominated by inorganic semiconductors. However, the high cost, complex fabrication techniques, and lack of mechanical flexibility have limited mass production and integration of these established mature inorganic semiconductor-based photodetectors with novel technologies. Some organic semiconductor-based photodetection devices have also been reported. The low-cost fabrication process, low-temperature solution-based preparation, ease of largearea production, lightweight, and mechanical flexibility make them strong competitors to inorganic semiconductors. However, organic semiconductor-based photodetectors have some major drawbacks, such as much slower operation and a limited life span compared with inorganic-based photodetectors. [6-8] In this regard, a new semiconducting material class known as metal halide perovskites (MHPs) has emerged as a possible alternative to inorganic and organic semiconductors. These MHP semiconductors have opened a new door in the field of optoelectronics. In particular, outstanding photoconversion efficiency of about 24% has been achieved for MHP-based photovoltaic devices within a decade of their introduction to photovoltaics. [9] This rapid achievement has encouraged many researchers to investigate new optoelectronic device applications beyond photovoltaics. Among these applications, the development of MHPbased photodetection devices is regarded as a new research hotspot. Importantly, MHPs have large absorption coefficients as high as 10 5 cm −1 , [10] which is one of the basic requirements for implementation in photodetection devices. Moreover, these MHPs possess long photocarrier transport lengths of at least 100 nm [11] and high charge carrier mobilities, which are also favorable for implementation in high-performance photodetectors. Tailorable absorption spectra is another exceptional optical characteristic of MHPs, so both broadband and narrowband absorption features are possible with MHP-based photodetectors. [12] In addition to the above features, MHPs have low-cost production facilities because they are solution-processable at low temperatures, like organic semiconductors. [13] These excellent optical and electrical properties of MHPs make them unique among photosensing materials, and they have a variety of applications. Although they have many positive aspects, there are still many challenges in enhancing the device performance Over the last few years, metal halide perovskites have established themselves as important materials in the field of optoelectronics. After their first application in photovoltaics, they have been successfully used in other optoelectronic devices, especially photodetectors, owing to their unparalleled optical and electronic properties. Notably, because of their unique optical and electronic properties and small physical dimensions, various carbon nanomaterials have emerged as alternatives for next-generation optoelectronic devices, and they have also been combined with other materials...
The combined effect of 13C isotope doping and vacancies on the phonon properties of a single-wall carbon nanotube is theoretically investigated using the forced oscillation method. The phonon density of states (PDOS) is calculated for all (0%–100%) 13C isotope contents and wide (0%–30%) vacancy concentrations. We found a redshift of the Raman active E2g peak in the PDOS with increasing isotope contents, while the disappearance of the E2g peak and the appearance of a new sharp peak in the low-energy region with increasing combined defects. Both 13C isotope and combined defects cause the localization of the high-energy optical phonons. We calculated the typical mode patterns for the in-plane longitudinal optical phonon to visualize the localization phenomena elaborately at the presence of isotope and vacancies. The calculated average localization length shows an asymmetric behavior with increasing 13C isotope concentrations which is in good agreement with the 13C isotope dependence localization length of single-layer graphene. We noticed that a typical localization length is on the order of ∼1 nm at 70% isotope concentrations. The combined effect of 13C isotope and vacancies shows an abruptly decreasing localization length with increasing defect densities. These results are important to understand the heat conduction as well as nanoscopic vibrational studies such as tip-enhanced Raman spectra in carbon nanotubes where the local phonon energies may be mapped.
Single wall carbon nanotube (SWCNT) is considered as an ideal candidate for next-generation nanoelectronics owing to its unusual properties.Here we have performed an in-depth theoretical analysis of the effect of vacancy defects and curvature on the phonon properties of ð10; 0Þ and ð10; 10Þ SWCNTs using the forced vibrational method. We report that Raman active E 2g mode softens towards the low-frequency region with increasing vacancies and curvature in both types of CNTs. Vacancy induces some new peaks at low-frequency region of the phonon density of states. Phonon localization properties are also manifested. Our calculated mode pattern and localization length show that optical phonon at Raman D-band frequency is strongly localized in vacancy defected and large curved CNTs. Our findings will be helpful in explaining the thermal conductivity, specific heat capacity, and Raman spectra in vacancy type disordered CNTs, as well as electron transport properties of CNT-based nanoelectronic devices.
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