Realizing a SnO2-based ultraviolet light-emitting diode via breaking the dipole-forbidden rule

Abstract

Although many oxide semiconductors possess wide bandgaps in the ultraviolet (UV) regime, currently the majority of them cannot efficiently emit UV light because the band-edge optical transition is forbidden in a perfect lattice as a result of the symmetry of the band-edge states. This quantum mechanical rule severely constrains the optical applications of wide-bandgap oxides, which is also the reason why so few oxides enjoy the success of ZnO. Here, using SnO 2 as an example, we demonstrate both theoretically and experimentally that UV photoluminescence and electroluminescence can be recovered and enhanced in wide-bandgap oxide thin films with 'forbidden' energy gaps by engineering their nanocrystalline structures. In our experiments, the tailored low-temperature annealing process results in a hybrid structure containing SnO 2 nanocrystals in an amorphous matrix, and UV emission is observed in such hybrid SnO 2 thin films, indicating that the quantum mechanical dipole-forbidden rule has been effectively overcome. Using this approach, we demonstrate the first prototypical electrically pumped UV-lightemitting diode based on nanostructured SnO 2 thin films.

Ultraviolet emission from low resistance Cu2SnS3/SnO2 and CuInS2/Sn:In2O3 nanowires

“…• C which is accompanied by a gradual suppression of the photoluminescence (PL) peak at 2.25 eV related to surface states of SnO 2 , and the emergence of a peak at 3.65 eV corresponding to band edge emission from electrostatically defined SnO 2 quantum dots in accordance with Li et al 28 These Cu 2 SnS 3 /SnO 2 NW assemblies have very low resistances of ≈100 Ω similar to that of ITO NWs. On the other hand, we observe the existence of the cubic bixbyite crystal structure of In 2 O 3 and chalcopyrite CuInS 2 obtained from Cu/Sn:In 2 O 3 NWs under H 2 S between 100 and 500…”

Brush-like SnO2/ZnO hierarchical nanostructure: Synthesis, characterization and application in UV photoresponse

“…Up to now, the photoluminescence mechanism of SnO 2 is still not clear. [43][44][45][46][47][48][49] It is believed that the surface oxygen vacancies defect states can induce direct gap transitions and generate possible photoluminescence. [43][44][45] Recently, Li et al found that that the SnO 2 nanostructures can break the dipole-forbidden rule and realize UV luminescence.…”

“…[43][44][45] Recently, Li et al found that that the SnO 2 nanostructures can break the dipole-forbidden rule and realize UV luminescence. 46 The HRTEM image of an individual SnO 2 nanowire shown in Figure 1(b) indicates the existence of surface defect states, which can induce the low symmetry of the surface structure and realize the effective UV emission from the SnO 2 nanowires. 46 Here, the UV emission band at 361 nm is attributed to band edge recombination of the photogenerated carriers, which may be originated from the conduction band to acceptors and neutral-donar-bound excitons.…”

“…46 The HRTEM image of an individual SnO 2 nanowire shown in Figure 1(b) indicates the existence of surface defect states, which can induce the low symmetry of the surface structure and realize the effective UV emission from the SnO 2 nanowires. 46 Here, the UV emission band at 361 nm is attributed to band edge recombination of the photogenerated carriers, which may be originated from the conduction band to acceptors and neutral-donar-bound excitons. [47][48][49] For the SnO 2 nanowires sample, the above XPS result reveals that oxygen vacancies are formed on the SnO 2 nanowire surface.…”

Experimental and first-principles study of ferromagnetism in Mn-doped zinc stannate nanowires

“…The nanowire dimensions were too large to construct models simulating modified surface band structures. 51 Thus, the calculations focused on the effect of defects on magnetic order. Three occupied configurations: (i) two NN Sn atoms, (ii) two NN Zn atoms and (iii) NN Sn and Zn atoms, were replaced by two Mn atoms.…”