In addition to the known effect of substrate on interfacial properties of perovskite films, here we show that bulk properties of Hybrid Lead Halide Perovskite films depend on the type of substrate used for film growth. Despite the relative large film thickness, ~600 nm, the roughness and nature of the substrate layer (glass, FTO, TiO 2 and PEDOT:PSS) affect not just the degree of preferential orientation and crystal grain size Raman peaks.The irreversible photoluminescence enhancement observed at low power with illumination time, also dependent on the substrate nature, is proposed to be due to the localization of the electron-hole excitons created in the vicinity of the light generated defects. The results shed light into the performance of the perovskite layer and help understanding how bulk processes, where ion migration is a conspicuous example, are severely affected by interfacial properties as those imposed by the substrate.

NaBi(WO 4 ) 2 (NBW), NaBi(MoO 4 ) 2 (NBMo) and LiBi(MoO 4 ) 2 (LBMo) single crystals grown by the Czochralski technique have been doped up to a praseodymium concentration of [Pr] ≈ 1 × 10 20 cm −3 in the crystal. 10 K polarized optical absorption and photoluminescence measurements have been used to determine the energy position of 32, 39 and 36 Pr 3+ Stark levels in NBW, NBMo and LBMo crystals, respectively. These energy levels were labelled with the appropriate irreducible representations corresponding to a C 2 local symmetry of an average optical centre. Single-electron Hamiltonians including free-ion and crystal field interactions have been used in the fitting of experimental energy levels and in the simulation of the full sequence of the 4f 2 Pr 3+ configuration. 300 K absorption spectra of different 2S+1 L J Pr 3+ multiplets were determined and used in the context of the Judd-Ofelt theory and for the calculation of the 1 D 2 -related emission cross sections of this average Pr 3+ centre. Non-radiative electron relaxation from the 3 P 0 level feeds the 1 D 2 multiplet. This latter level efficiently decays radiatively to the ground 3 H 4 multiplet but still there is a significant rate of radiative decay to the 1 D 2 → 3 F 3 praseodymium laser channel. For [Pr] 2 × 10 19 cm −3 , non-radiative electric dipole-dipole Pr pair energy transfer limits the radiative yield.

Solution-processed near-infrared organic light-emitting diodes (NIR-OLEDs) with structure glass/indium–tin oxide/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)/Er-complex/Ca/Al based on a novel Er(III) complex, [Er(tfnb)3(bipy)] (Htfnb = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione and bipy = 2,2′-bipyridine) have been manufactured and their properties have been studied. A complete quenching of the organic ligand visible emission is shown, and only the sensitized 1.5 μm electroluminesce from Er(III) results. From the electrical characteristic we present the mobility dependence on applied voltage using a numerical model, comparing it to poly(9,9-dioctylfluorene), a commercial semiconducting polymer with optical properties close to those of the molecular ligands. The synthesis of the novel complex together with a detailed analysis of its structure elucidated by XRD, 1H NMR, Raman, and Fourier-transform infrared spectroscopies is presented. A wide-ranging characterization of its photophysical properties in terms of absorption and steady and transient photoluminescence is used to investigate the energy-transfer process from the organic ligand to the central Er(III) ion.

Three novel ternary Er 3+ complexes emitting in the C band transmission window for fiber optic communications have been synthesised and their structures have been elucidated by single crystal X-ray diffraction. The fluorinated b-diketonate ligand, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, combines a good absorption cross-section in the ultraviolet region with reduction of non-radiative quenching of the Er 3+ emission, while the rigidity and bulkiness of the three different N,N-donors (2,2 0 -bipyridine, bathophenanthroline and 5-nitro-1,10-phenanthroline) have a pronounced impact on the emission intensity of luminescence. Furthermore, the choice of the ancillary ligand also determines the efficiency of the antenna effect, leading to complete quenching of the ligand-associated visible emission for the optimized complex with 5-nitro-1,10-phenanthroline. Solution processed 1.54 mm organic light-emitting diodes have been manufactured and characterized for this complex, confirming the aforementioned complete resonant energy transfer from the ligands to the Er 3+ ion. The features of the reported device fabrication show a simple way to obtain large area NIR-OLEDs.

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