Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Charge transport in an organic light emitting diode material measured using metal-insulator-semiconductor charge extraction by linearly increasing voltage with parameter variation

Charge transport measurement using the Metal-Insulator-Semiconductor Charge Extraction by Linearly Increasing Voltage (MIS-CELIV) technique is a promising method for determining charge mobility in organic semiconductors because of its ability to study electron and hole mobilities independently. However, MIS-CELIV measurements have a number of parameters that can potentially affect the calculated mobility. There are only a few reports on MIS-CELIV being used to determine the charge mobility for materials typically used in organic light-emitting diodes (OLEDs), and the impact of each of the MIS-CELIV experimental parameters on the mobility is presently unknown. We find that the pulse duration, injection time, maximum voltage, offset voltage, and external load resistance have different levels of influence on the calculated mobility. Using the hole transporting OLED host material, tris(4-carbazoyl-9-ylphenyl)amine (TCTA), we show that having an injection time sufficient to fully charge the insulator layer, a pulse duration comparable to the transit time, and an external circuit time constant much smaller than the transit time is required to give a mobility relevant to an OLED. The optimized MIS-CELIV parameters led to the measurement having a similar current density and electric field to that of an operational OLED. Under these conditions, the hole mobility of TCTA was determined to be 2.90 ± 0.07 × 10 cm V s, which is similar to that measured using time-of-flight techniques. Using inappropriate experimental parameters could lead to an underestimation of the mobility by an order of magnitude. Simulations of the MIS-CELIV measurements verified the effect the different parameters played in determining the charge mobility

Revealing the interplay between charge transport, luminescence efficiency, and morphology in organic light‐emitting diode blends

Phosphorescent emissive materials in organic light-emitting diodes (OLEDs) manufactured using evaporation are usually blended with host materials at a concentration of 3–15 wt% to avoid concentration quenching of the luminescence. Here, experimental measurements of hole mobility and photoluminescence are related to the atomic level morphology of films created using atomistic nonequilibrium molecular dynamics simulations mimicking the evaporation process with similar guest concentrations as those used in operational test devices. For blends of fac-tris[2-phenylpyridinato-C2,N]iridium(III) [Ir(ppy)] in tris(4-carbazoyl-9-ylphenyl)amine (TCTA), it is found that clustering of the Ir(ppy) (surface of the molecules within ≈0.4 nm) in the simulated films is directly relatable to the experimentally-measured hole mobility. Films containing 1–10 wt% of Ir(ppy) in TCTA have a mobility of up to two orders of magnitude lower (≈10 cm V s) than the neat TCTA film, which is consistent with the Ir(ppy) molecules acting as hole traps due to their smaller ionization potential. Comparison of the simulated film morphologies with the measured photoluminescence properties shows that for luminescence quenching to occur, the Ir(ppy) molecules have to have their ligands partially overlapping. Thus, the results show that the effect of guest interactions on charge transport and luminescence are markedly different for OLED light-emitting layers

Improved Performance of Photomultiplication Polymer Photodetectors by Adjustment of P3HT Molecular Arrangement

A series of photomultiplication (PM)-type polymer photodetectors (PPDs) were fabricated with polymer poly­(3-hexylthiophene)–[6,6]-phenyl-C₇₁-butyric acid methyl ester (P3HT–PC₇₁BM) (100:1, w/w) as the active layers, the only difference being the self-assembly time of the active layers for adjusting the P3HT molecular arrangement. The grazing incidence X-ray diffraction (GIXRD) results exhibit that P3HT molecular arrangement can be adjusted between face-on and edge-on structures by controlling the self-assembly time. The champion EQE value of PPDs, based on the active layers without the self-assembly process, arrives at 6380% under 610 nm light illumination at −10 V bias, corresponding to the face-on molecular arrangement of P3HT in the active layers. The EQE values of PPDs were markedly decreased to 1600%, along with the self-assembly time up to 12 min, which should be attributed to the variation of absorption and hole transport ability of the active layers induced by the change of P3HT molecular arrangement. This finding provides an effective strategy for improving the performance of PM-type PPDs by adjusting the molecular arrangement, in addition to the enhanced trap-assisted charge-carrier tunneling injection

Precursor route poly(1,4-phenylenevinylene)-based interlayers for perovskite solar cells

Insoluble glycol-derivatized poly(1,4-phenylenevinylene)s (PPVs) have been prepared by in situ thermal conversion of solution-processable xanthate precursor polymers and used as interlayers in inverted perovskite solar cells. The insolubility of the PPVs enabled the perovskite active layer to be deposited on top without dissolution, and the glycol chains provided a suitable surface energy for the formation of the perovskite films. It was found that the surface of the films became more hydrophilic with increasing glycol side-chain length. The energy levels of the PPVs indicated they were appropriate for hole transport and electron blocking with respect to the perovskite layer. The performance of the perovskite cells was found to be dependent on the length of PPV glycol side-chain with the optimized planar p-i-n perovskite devices incorporating an MeO-PPV/PFN-P2 hole-extracting interlayer exhibiting a champion power conversion efficiency of 12.1%