Injection and Charge Transport

In the following section an overview, of several models describing the charge carrier injection and transport of LEDs based on polymers and organic materials, is presented. The focus will be set on metal/polymer (organic material)/metal contacts based on a polymer with a low defect concentration will be discussed. A description of LEDs, based on polymers with a high defect concentration, can 

---

The semiconductor structure is crucial for both electron injection and charge transport after the exciton separation. Meng et al. [35] published a theoretical study focused on the electron injection mechanism in dyad anthocyanine-Ti02 nanowires. 

As aforementioned, the introduction of carbon nanomaterials is an effective strategy to take on some of the contemporary challenges in the field of DSSCs. In particular, enhanced charge injection and charge transport processes in carbon nanomaterial-doped electrodes, efficient carbon nanomaterial-based, iodine-free, quasi-solid state electrolytes, and the use of novel nanographene hybrids as dyes are some of the most stunning milestones. All of these milestones are considered as solid proof for the excellent prospect of carbon nanomaterials in DSSCs. The major goal of this chapter is to... 

Enhancement in the performance of OLEDs can be achieved by balanced charge injection and charge transport. The charge transport is related to the drift mobility of charge carriers. Liu et al. [166] reported blue emission from OLED based on mixed host structure. A mixed host structure consists of two different hosts NPB and 9,10-bis(2 -naphthyl)anthracene (BNA) and one dopant 4,4 -bis(2,2-diphenylvinyl)-l,l -biphenyl (ethylhexyloxy)-l,4-phenylene vinylene (DPVBi) material. They reported significant improvement in device lifetime compared to single host OLEDs. The improvement in the lifetime was attributed to the elimination of heterojunction interface and prevention to formation of fluorescence quenchers. Luminance of 80,370 cd/m2 at 10 V and luminous efficiency of 1.8 cd/A were reported. 

In the case of the polymer strands oriented perpendicularly to the electrodes surface, the processes of charge injection and charge transport are strongly dependent on the morphology of the polymer layer. First, since all the strands are perpendicular... 

Electron Injection and Charge Transport in Polymer Light Emitting Devices... 

As can be deduced from equation (1), the optimizations of charge-injection and charge-transport (both of which directly influence the fraction of injected charge carriers that form excited states, qr) are important aspects for the design... 

In order to analyze the interplay between charge injection and bulk conductivity, one must use specific models for both injection and charge transport in bulk. Here we treat the charge injection as diffusion-controlled and the transport is multiple trapping theory. 

Under reverse bias, the band bending and its associated electric field are increased by the applied voltage, and charge transport across the junction is blocked. Conversely, under forward bias, the external voltage tends to decrease the band bending, thus facilitating charge injection across the interface. Eq. 

As pointed out before, interfaee stmeture in OFETs is important for both charge injection (metal-semiconductor interface) and charge transport (semi-conductor-dielectric interface). The discussion of the previous section demonstrates that even for the small number of model systems considered here a large variety of sfructures is observed. Because many factors influence the interface and film sfructures, it is difficult to establish general mles. Flowever, a few important observations regarding the stmcture-forming factors can be kept hold of ... 

Here I, represents the drain current and ju, jUp the respective electron and hole mobility. C defines the area capacitance of the insulator. The channel geometry is defined by the channel width W and length L. The ambipolar range, described by Eq. (3), is only valid as long as both electrons and holes can be injected and further transported in the active layer of the transistor. However, in most cases the injection and/or the transport in the transistor channel are suppressed for one charge carrier type. In that case, the FET operates only in the unipolar and saturation range as described by Eqs. (1) and (2). 

Schematic energy diagram of the NPB single-layer devices, and energy transfer mechanism of perylene-doped device includes 1, carrier injection 2, charge transport in pristine NPB 3, electrons and holes are trapped and recombine and 4, light emission.

Figure 3.1 Schematic illustration for charge injection barrier (energy level alignment) and charge transport in an organic field-effect transistor using hole transport. The upper part depicts a typical structure of OFET and the...

---