Molecularly doped polymers

In molecular doped polymers the variance of the disorder potential that follows from a plot of In p versus T 2 is typically 0.1 eV, comprising contributions from the interaction of a charge carrier with induced as well as with permanent dipoles [64-66]. In molecules that suffer a major structural relaxation after removal or addition of an electron, the polaron contribution to the activation energy has to be taken into account in addition to the (temperature-dependent) disorder effect. In the weak-field limit it gives rise to an extra Boltzmann factor in the expression for p(T). More generally, Marcus-type rates may have to be invoked for the elementary jump process [67]. 

There have been numerous studies of the electrical and emission properties of conjugated polymer-, small molecule-, and molecularly doped polymer-based OLEDs. The current-voltage and radiance-voltage characteristics have been nica sured as a function of thickness of the organic layer, temperature, different metal electrodes, etc. in an attempt to understand the device physics. A major factor in hibiting progress is the purity of the organic impurities that are incorporated dur-... 

J Kido, M Kohda, K Okuyama, and K Nagai, Organic electroluminescent devices based on molecularly doped polymers, Appl. Phys. Lett., 61 761-763, 1992. 

Dunlap DH, Parris PE, Kenkre VM (1996) Charge-dipole model for the universal field dependence of mobilities in molecularly doped polymers. Phys Rev Lett 77 542... 

Hirao A, Nishizawa H, Sugiuchi M (1995) Diffusion and drift of charge carriers in molecularly doped polymers. Phys Rev Lett 75 1787... 

Schein LB, Glatz D, Scott JC (1990) Observation of the transition from adiabatic to nonadiabatic small polaron hopping in a molecularly doped polymer. Phys Rev Lett 65 472... 

Schein LB, Tyutnev A (2008) The contribution of energetic disorder to charge transport in molecularly doped polymers. J Phys Chem C 112 7295... 

Borsenberger PM, Bassler H (1991) Concerning the role of dipolar disorder on charge transport in molecularly doped polymers. J Chem Phys 95 5327... 

Time-of-flight experiments have been used for over three decades to characterize carrier mobilities in crystal, and polycrystalline and disordered organic solids including molecularly doped polymers and molecular glasses [28,424,430,431]. Relatively high values (up to several hundreds cm2/V s) and hot carrier effects have been observed in... 

Figure 109 Poole-Frenkel-type plots of the field dependent mobility in a molecular-doped polymer (TAPC PC) at different temperatures. A change from the negative to positive value of [see Eq. (265)] is well pronounced at T > 240 K. After Ref. 479. Copyright 1991 American Institute of Physics.

Figure 169 External quantum efficiency of molecularly doped-polymer-based SL LEDs from Fig. 151 as a function of electric field (a), and recombination-to-transit time ratio for three of them, obtained from Eqs. (315) and (317) with P = Ps = 0.25, = 0.6 and (pT = 11% for LEDs 1,2 and 3, respectively (b). After Ref. 389. Copyright 2001 Institute of Physics (GB), with permission.

Table 8.2 Mobilities in semiconducting and molecularly doped polymers...

Different classes of polymers and molecular solids exhibit systematically distinct ranges of values of A and V. For t)rpical gendant-group and molecularly doped polymers, O.leV i A S. leV,... 

ILECTRONIC TRANSPORT IN AMORPHOUS SOLIDS and in random organic media in particular has been the subject of vigorous scientific activity for more than 2 decades. The approach taken in this chapter is to integrate recent studies of electronic transport in polysilanes with the extensive earlier work on poly(N-vinylcarbazole) (PVK) and molecularly doped polymers (MDPs) (i,e., systems in which transport-active molecular species are dispersed in an inert binder) and thereby allow the distinctive features of transport in the Si-based systems to emerge. 

Molecularly Doped Polymers. Work on molecularly doped polymers (MDPs), which are dispersions of transport-active molecular species in inert polymeric binders, evolved directly as a result of mechanistic insights gained from the numerous preceding studies of polymers and charge-transfer complexes. A number of hole-transport studies have been carried out on substituted aromatic amines 13, 31, 38-42) with polycarbonate (PG) used as an inert binder. Results on the system N,N -diphenyl-N,N, N -bis(3-meth-ylphenyl)- , -diphenyl-4,4 -diamine (TPD) in bisphenol A-PG are illustrative (12). 

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