Abstract—Light-emitting organic field-effect transistors (LE-FETs) on the basis of composite films that consist of perovskite nanocrystals (CsPbBr_3) embedded in a matrix of conjugated polymer—polyfluorene (PFO)—have been obtained, and their electrical and optical properties have been investigated. Output and transfer current-voltage characteristics (I-Vs) of FETs based on PFO : CsPbBr_3 films (component ratio 1 : 1) have a slight hysteresis at temperatures of 100–300 K and are characteristic of hole transport. The hole mobility is ∼3.3 and ∼1.9 cm^2/(V s) at the modes of the saturation and low fields, respectively, at 250 K and reaches ∼5 cm^2/(V s) at 100 K. It has been shown that the application of pulsed voltage to LE-FETs based on PFO : CsPbBr_3 can reduce the ionic conductivity and provide electroluminescence in this structure at 300 K.
The paper reports on molecular beam epitaxy of ZnSe/InSe/ZnSe quantum well (QW) heterostructures grown on GaAs(001) substrates as well as studies of their structural properties. The structures were characterized by reflection high energy electron diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy techniques. The evolution of surface morphology of QW heterostructures as a function of the InSe thickness has been studied. The quasi van der Waals growth of ZnSe on the InSe(0001) surface has been demonstrated, with the ZnSe(111) plane being oriented parallel to the (0001) plane of InSe because of a small lattice mismatch between InSe and ZnSe(111).
Crystal phase and strain engineering in epitaxial nanowire (NW) heterostructures provide a widely tunable functionality for future nanoscale light emitters and photodetectors. Thus, InAs band gaps can be finely tuned in the midinfrared range by introducing a mechanical strain through lattice mismatch in core−shell NWs. Here, we demonstrate that the inhomogeneity of the InP shell thickness leads to a non-uniform stress field and a local variation in the degree of surface passivation along the InAs NW length which both have a strong effect on the recombination mechanisms. Catalyst-free InAs NWs with a coherent nanometer thick InP shell were grown on Si(111) by means of molecular beam epitaxy. Temperature-dependent photoluminescence (PL) studies (5−150 K) allow us to distinguish the surface passivation and strain-induced effects. Nontrivial temperature dependence in contrast to the expected monotonic band gap shrinkage with temperature was found. At high temperatures (100−150 K), radiative recombination predominantly occurs in the NW regions, which have a thicker InP shell and, as a result, are free from surface states. In turn, the coherently grown InP shell induces a tensile strain in the InAs NW core and leads to a blue shift in an emission energy by a 45−50 meV at 100 K. In contrast, at low temperatures (<100 K), the PL band undergoes a red shift with decreasing temperature since photogenerated carriers are able to radiatively recombine at band gap energy minima at the unstrained NW regions. According to the performed ab initio calculations, observed emission is attributed to the interband optical transitions of the hexagonal InAs polytype with an intermediate band gap energy (435 meV at 5 K) lying between the zinc-blende and wurtzite values. Current observations are in a great demand for stressinduced band gap tuning in the functional nanoheterostructures.
The optical absorption spectra and structural properties of samples series consisting of AZO oxide films with an intermediate layer of silver nanoparticles with different sol compounds were investigated. TEM analysis of the obtained coatings showed that the nanoparticles in the AZO film form an ordered structure, and the distance between them depends on the sol composition and the film annealing temperature. Optical measurements showed that a position of the nanoparticle plasmon peak in AZO also depends on them.
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