Heterojunctions mixed

Xue JG, Rand BP, Uchida S, Eorrest SR (2005) A hybrid planar-mixed molecular heterojunction photovoltaic cell. Adv Mater 17 66... 

Xue JG, Uchida S, Rand BP, Forrest SR (2004) Asymmetric tandem organic photovoltaic cells with hybrid planar-mixed molecular heterojunctions. Appl Phys Lett 85 5757... 

Wynands D, Levichkova M, Riede M, Pfeiffer M, Baeuerle P, Rentenberger R, Dernier P, Leo K (2010) Correlation between morphology and performance of low bandgap oligothiophene C6o mixed heterojunctions in organic solar cells. J Appl Phys 107 6... 

One of the most promising uses of C60 involves its potential application, when mixed with 7r-conjligated polymers, in polymer solar cells. Most often the so-called bulk heterojunction configuration is used, in which the active layer consists of a blend of electron-donating materials, for example, p-type conjugated polymers, and an electron-accepting material (n-type), such as (6,6)-phenyl-Cgi -butyric acid methyl ester (PCBM, Scheme 9.6).38... 

The use of low bandgap polymers (ER < 1.8 eV) to extend the spectral sensitivity of bulk heterojunction solar cells is a real solution to this problem. These polymers can either substitute one of the two components in the bulk hetero junction (if their transport properties match) or they can be mixed into the blend. Such a three-component layer, comprising semiconductors with different bandgaps in a single layer, can be visualized as a variation of a tandem cell in which only the current and not the voltage can be added up. 

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. 

Several organics, e.g. pristine poly(3-octylthiophene), polyfluorene, bifunctional spiro compounds and polyphenyleneethynylene derivative, have been used for fabricating photOFETs. Responsivity as high as 0.5-1 A/W has been achieved in some of these transistors. We have already discussed the bulk heterojunction concept in Chapter 5. The bulk heterojunctions are fabricated using acceptor materials with high electron affinity (such as C<5o or soluble derivatives of C6o) mixed with conjugated polymers as electron donors. PhotOFETs based on conjugated polymer/fullerene blends are expected to show... 

XueJ. G., Rand B. P., Uchida S. and Forrest S. R. (2005), Mixed donor-acceptor molecular heterojunctions for photovoltaic applications. 11. Device performance , J. Appl. Phys. 98, 124903-1-124903-9. 

It is now also clear what the polymer film equivalent of the concentration of a solution has to be. A highly concentrated solution results in a high frequency of collisions. In a polymer blend film excitons encounter heterojunctions more frequently when the hetero junction density is high. Hence, a high concentration of a solution corresponds to a well-mixed polymer blend with small-scale phase separation. The degree of mixing of the components in a polymer blend (i.e. the... 

Recently, Foreman demonstrated that fe-linear terms in semiconductor heterojunctions [47] are enhanced near the interface, and that the associated mixing of Fg hh and Ih states is increased so that it influences the quantum-well Pockels effect. [48] The reduced symmetry in quantum well structures (from Td in the bulk to C2v) increases the optical anisotropy. The work in Ref. [47] shows that the A -linear splitting contributes significantly to this anisotropy because the C coefficients are often an order of magnitude larger in the heterojunctions than in the bulk materials. 

The mixed alloy arsenides are important to a wide range of optoelectronic applications. The addition of A1 to GaAs allows for compositional control of the bandgap and formation of heterojunctions from various alloys written as Al Gai- As. In turn, a great variety of devices may be fabricated. A difficulty in fabricating these alloys is the reactivity of Al. A1 and its primary sources TMAl and TEAl are very reactive to oxygen. TMAl is the most popular reactant. Oxygen incorporation readily occurs because AlyO precipitates are involatile (GaO which readily evaporates from the deposition... 

Device Performance of CuPcrQo Mixed Heterojunction Photovoltaic Cells... 

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