Donor materials

In another work, the same authors demonstrated the versatility of graphene as donor material when preparing a similar nanographene hybrid with porphycenes, a well-known electron acceptor [120], The preparation was followed along the same lines that were established for the porphyrins. By using Raman, TEM, and AFM, the nature of the graphene moiety was clearly demonstrated. Contrary to the electron ac-... 

Ti hydride/K perchlorate mixts have been found to be good donor materials (Ref 28) when initiated with a bridgeware or mild detonating fuze, affording the possibility of utilization ini electric detonators which function with delays ranging from 25 msec to 3 sec. Whereas no fundamental studies have been found on the shock initiation of Zr hydride, its response must be considered comparable with that of Ti hydride for whose shock initiation an excellent study was recently published (Ref 31). Methods for estimating internal energies of pyrotechnic mixts in the absence of shock initiation studies were described by Hardt and Martinson (Ref 22)... 

Both phthalocyanines and squaraines are good candidates for bulk heterojunction solar cells. Recently, a supramolecular hetero-array of these functional dyes Pc-Sq-Pc (compound 52) has been reported for the first time, which exhibits a large coverage of the solar spectrum from 250 to 850 nm [51]. This axially held assembly serves as a robust panchromatic sensitizer. Upon excitation, it forms the radical ion pair Pc+-Sq -Pc with a long lifetime of 24 2 p,s. The use of this assembly as a donor material in solution processable bulk heterojunction solar cells has also been briefly studied. 

Despite attempts to increase efficiency using lower optical gap materials, the highest power conversion efficiencies are still achieved using CuPc as the donor material and Ceo as acceptor. The most important improvements have come about through improved device design. Key developments include the following ... 

Mihailetchi et al, 2004), when the electrodes of the device make ohmic contacts with the acceptor and donor materials. Progress in nnderstanding the origin of the open-circuit voltage of organic solar cells and its dependence on device parameters will be discussed in Section 7.6.2 below. 

Once the charge carriers have been successfully separated, they need to be transported to the respective electrodes to provide an external direct ciu rent. Here the donor material serves to transport the holes whereas the electrons travel within the acceptor material. Thus, percolation paths for each type of charge carrier are required to ensure that the charge carriers will not experience the fate of recombination due to trapping in dead ends of isolated domains [60-62]. As such the bulk heterojunction has to consist of percolated, interpenetrating networks of the donor and acceptor phases. 

Si has 4 valence electrons while P has 5 and In 3. If we introduce a very small amount of phosphorus into silicon, the phosphorus atoms substitute for silicon in the crystal lattice. Each such phosphorus has an excess of 1 electron. These electrons are not free but are very weakly bound, such that only 0.04 eV is needed to transfer them into the conduction bands. Because phosphorus donates extra electrons to the system, it is referred to as a donor material. Silicon which contains small amounts of donor material (usually referred to as... 

HGURE 5.2 (A) Structures of conducting polymers. (B) Representative high performance donor materials in polymer solar cell. (C) Representative fused aromatic ring building blocks for high performarxe donor materials. 

With other substitutes group instead of alkyl side chains, the energy levels of acceptor polymer can be modified to match that of donor materials. Fluoro-substituted n-type conjugated polymers were introduced for all-polymer solar cells with the highest reported energy conversion efficiency of 6.71% at the state of art (Jung et al, 2015). 

Another interesting nanoblending strategy is to blend the donor polymer with a sacrificial-insulating-polymer-based template that forms self-assembled nanostructures and acts as a PDA [438]. The chosen PDA polymer is soluble in a solvent that don t at all dissolve donor, so that once the film (active layer) has been deposited, the PDA can be selectively dissolved leaving behind a porous nanostructured pool of donor material, that... 

In solar cells, the absorption of incident photons on donor material subsequently leads to generation of excited electron-hole pair which is better known as exciton. The dissociation of excitons is necessary to generate free carriers (electrons and holes). However, in CP-based donor materials, high exciton dissociation energy (due to the low electric permittivity and localized electron and hole wave functions) makes their separation into free... 

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