Electron injection and charge

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. 

Katoh R, Furabe A, Barzykin, Arakawa H, and Tachiya H (2004) The kinetics and mechanism in electron injection and charge recombination in dye-sensitized nanociystalline semiconductor. Coord Chem Rev 248 1195-1213... 

Fig. 1. Rise of the perylene cation absorption, which reflects the electron injection dynamics, after excitation of the first singlet state with a 15 fs pump pulse. Variation of the electronic coupling via a change in the anchor group as well as the insertion of one or two -CH2- groups leads to a systematic change in the time scale of both electron injection and charge recombination.

R. Katoh, A. Furube, A.V. Barzykin, H. Arakawa, M. Tachiya, Kinetics and mechanism of electron injection and charge recombination in dye-sensitized nanocrystalline semiconductors (review) . Coordination Chemistry Reviews 248, 1195-1213, (2004). 

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

Kinetics and thermodynamics of electron injection and charge recombination DNA hairpins possessing a stilbenediether electron donor linker observed with neighboring cytosine or thymine bases obtained by femtosecond transient absorption spectroscopy were investigated [12]. 

Chang Y-C, Wu H-P, Reddy NM et al (2013) The influence of electron injection and charge recombination kinetics on the performance of porphyrin-sensitized solar cells effects of the 4-tert-butylp3rtidine additive. Phys Chem Chem Phys 15(13) 4651-4655... 

Steyrleuthner R, Schubert M, falser E, Blakesley JC, Chen Z, Facchetti A, Neher D (2010) Bulk electron transport and charge injection in a high mobility n-type semiconducting polymer. Adv Mater 22 2799... 

The charge-recombination process between injected electrons and oxidized dyes must be much slower than the process of electron injection and electron transfer from the I ion into oxidized dyes (i.e., regeneration of dyes) to accomplish effective charge separation. It was reported that charge recombination -... 

A number of different approaches can be taken to investigate the charge-injection process. The first one, outlined in the last section, is based on the absorption rise observed at about 1200 nm which is associated with the presence of electrons in TiC>2. A second method is based on the measurement of the IPCE values for the assemblies in the presence of iodide, while the third approach is based on the intrinsic spectroscopic features of the sensitizer. In this present section, the focus is on the latter two approaches since the absolute rate for charge injection is not of direct interest but simply whether or not injection is taking place. To estimate the injection and charge-separation process, the transient absorption spectra of the sensitizer in solution are compared with those obtained in the interfacial supramolecular assembly. A typical example of this approach is shown in Figure 6.17 for the compound [Ru(dcbpy)2(bpzt)] [8], (see Figure 6.7 above for the structure). 

The novel ETM B3PYMPM was reported to have high electron mobility and relatively low LUMO level. The combination of these properties led to effective electron injection and transport from the cathode into the ETL of B3PYMPM. TAPC used in EBL on the anode side of the EML is a well-known HTM with a high triplet energy of 2.89 eV and a hole mobility of at least 7 X10 cm /V/s.i Thus, extremely efficient charge-transporting materials... 

All the polymers containing aromatic oxadiazoles were found to be easily n-doped whereas they were difficult to p-dope as revealed by cyclic voltamme, indicating that they possess electron injection and hole blocking properties which make them suitable for use as charge transporting layers in multilayer polymer LEDs. It was also shown that oxadiazole polymers can used as emissive materials. 

The different TSPcMt monomers showed transients of similar shape indicating similar relative rates of electron injection and regeneration. As compared to TSPcSi(OH)2, however, smaller ratios of charging/steady-state and discharging/steady-state currents were observed at TSPcZn and TSPcAl(OH) on ZnO (Figure 10.13) . A faster charge transfer from TSPcZn or TSPcAl(OH) to the electrolyte was thereby indicated relative to the injection rate to ZnO. Since lower steady-state values of the photocurrents were observed... 

As in all potentiostatic techniques, the double layer charging is a parallel process to the faradaic reaction that can substantially attenuate the photocurrent signal at short-time scale (see Section 5.3)" . This element introduces another important difference between fully spectroscopic and electrochemical techniques. Commercially available optical instrumentation can currently deliver time resolution of 50 fs or less for conventional techniques such as transient absorption. On the other hand, the resistance between the two reference electrodes commonly employed in electrochemical measurements at the liquid/liquid interfaces and the interfacial double layer capacitance provide time constants of the order of hundreds of microseconds. Consequently, direct information on the rate of heterogeneous electron injection from/to the excited state is not accessible from photocurrent measurements. These techniques do allow sensitive measurements of the ratio between electron injection and decay of the excited state under pho-tostationary conditions. Other approaches such as photopotential measurements, i.e. relative changes in the Fermi levels in both phases, can provide kinetic information in the nanosecond regime. 

The second critical property to be tuned is the efficiency of charge injection, which is determined by the energy barrier between the HOMO and the anode (for hole injection) and between the LUMO and the cathode (for electron injection), and of charge transport which is controlled by intermolecular... 

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