Electric-field dependent photoluminescence

The authors showed by applying the Onsager model to electric field-dependent photoluminescence quenching data [49,247,248] that the gemi-... 

The carrier generation mechanism in PPV has been addressed by studying the transient photoconductivity and the photoluminescence as a function of the external electric field, E, in samples oriented by tensile drawing [166]. The transient photocurrent is proportional to E at low fields, but increases nonlinearly for E> 10 V/cm. The field at which the photoconductivity becomes nonlinear (the onset field, EP ) depends on the degree of alignment the higher the draw... 

The photoconductivity (AIp /Ip, ) and the photoluminescence quenching ( - AIl(E)/Il) obtained at 77 K are plotted versus the bias field in Fig. VD-1. The data indicate clearly that the onset field for the nonlinear photocurrent, EP " = 0.77 X 10 V/cm, is lower by about 50% than the onset field of the luminescence quenching, EP =1.7x 10 V/cm. Below E5 the photocurrent is linearly dependent on E, and below E, the luminescence is field independent. At the highest electric fields employed in the transient photoconductivity experiment (E = 2.8x10 V/cm), - AIl(E)/Il 0.30, whereas the photocurrent increases beyond the linear extrapolation by a factor of = 6.3. 

It was previously demonstrated theoretically [1] and experimentally [2] that semiconductor quantum dots (QDs) show strong dependence of optical properties on an electric field. Chemically synthesized semiconductor nanorods also exhibit the electric field effects. For example, quantum-confined Stark effect and luminescence quenching of single nanorods were previously demonstrated [3-5]. Unlike QDs, the nanorods exhibit quantum confinement only in two dimensions. It is reasonable to assume that the electric field applied along a nanorod may result in the strong polarization dependence of photoluminescence (PL). In the present paper, we investigate the influence of an external electric field onto luminescent properties of chemically synthesized CdSe/ZnS nanorods. 

The electrical characterization was performed by means of DC measurements. The optical characterization included temperature-dependent (10-100 K) photoluminescence (PL) spectroscopy at low excitation (325 nm, 2 W/cm2), and low-temperature (10 K) reflection spectroscopy. Photoreflectance (PR) spectra were measured using the same HeCd laser beam with a power density of 0.1 mW/cm2 for modulation of internal electric fields. 

The displacement of the singlet excitons and the temperature effects, which should increase with the field or the electric power, also fail to describe the observed field dependence of the PL. The effect of temperature quenching on the photoluminescence is described below. 

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