Tetrafluoro-TCNQ

Through reduction or oxidation of the molecule by a dopant molecule. Atoms or molecules with high electron affinity, such as iodine, antimony pentafluoride (SbCls), or 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), may oxidize a typical organic semiconductor such as poly(p-phenylene) derivatives, leaving them positively charged. Reduction, i.e., addition of an electron, may be obtained by doping with alkali metals. 

Thin layers of PTCBI (50 A thick) and BCP (75 A thick) are used as the EBL in the front and back subcells, respectively, thereby forming a high efficiency double HJ PV structure (Peumans et al., 2000). A CRZ consisting of Ag nanoclusters (-5 A average thickness) buried in a 50 A thick 4,4, 4"-tris(3-methyl-phenyl-phenyl-amino)triphenylamine (m-MTDATA) p-doped with 5 mol% tetrafluoro-tetracyano-quinodimethane (F4-TCNQ) (Maeimig et al., 2004) was employed to connect the two subcells in series, where electrons generated in the front cell and holes generated in the back cell recombine. 

Figure 8.16. Chemical structure of (a) 7,7,8,8-tetracyanoqui-nodimethane (TCNQ) and (b) 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF4).

TCNQ = 7,7, 8,8 -tetracyanoquinodimethane, fluoranil = 2,3,5,6-tetrafluoro- -benzoquinone, TCNE = tetracyanoethylene, HCBD = hexacyano-butadiene, pmda = pyromellitic dianhydride, do-A = donor-acceptor interplanar distance. 

---