Photoactive devices

A methanofullerene derivative possessing an ammonium subunit has been prepared and subsequently shown to form a supramolecular complex with a porphyrin-crown ether conjugate <06T1979>. The synthesis and study of these fullerene-containing supramolecular photoactive devices have also been reported <06CRC1022>. 

Photoswitchable materials could be important components in molecular-scale electronic devices and several new systems have been reported. There have been other investigations of phototropic systems in which light is used to drive a reversible conformational change " or, in the case of liquid crystals, a phase transformation. Such photosystems are of interest for the engineering of microscopic photoactive devices but the subject is still in its infancy and practical devices remain elusive. Much more subtle is the use of light to trigger a change in... 

Because of limitation of this chapter, only a few properties of photoresponsive polymers are described. Table II includes several other properties so far reported(27-50). All of these physical and chemical properties are found to be controlled reversibly by photoirradiation. It is now generally accepted that photochromic reactions are useful as a tool to photo-control the properties of synthetic polymers. The photoresponsive polymers have potential applications for many photoactive devices, such as sensors, switches, memories, photo-mechanical transducers and so on. 

Consult reference (4) for the trade names of the resins applicable to the entries in this table. PVB as binder polymer in optoelectronic/photoactive devices ... 

Thus, many synthetic photoactive devices performing electronic or energetic transfers appear frequently in the literature. Due to the importance of this relatively young research field, an exhaustive coverage of the literature up until the end of 2001 (over 400 references, by Pierre Harvey, Sherbrooke, Quebec) has appeared in the second set of the Porphyrin Handbook. Our coverage will start from the end of 2001 and end in February 2004. A fewer number of references complementary to those analyzed by Harvey will be added. It should be noted, as reflected by the title of this chapter, that only systems involving more than one porphyrin will be covered in this chapter. Donor-acceptor (D-A) dyads involving only one porphyrin as either D or A will be omitted. 

The long lifetime and high quantum yield of the CS state of these donor-fullerene linked molecules seem to be efficient charge-generation species in the photoactive devices. A photoelectrochemical cell has been developed using a gold electrode which is covered by self-assembled mono-layers of porphyrin- Qo dyad with S-Au interaction [137]. 

In the previous section, devices with fullerenes as initial photoinduced electron acceptors in blends with conjugated polymers were discussed. Clearly one of their disadvantages is that only one of the two components is photoactive in the charge... 

The first resist used to fabricate solid-state devices was a negative resist based on cyclized poly(cis-1,4-isoprene) which is crosslinked using a photoactive bis-... 

These systems are based on immersion of two photoactive electrodes in an electrolyte solution with connection via an external circuit. An overall solar-spectrum hydrogen conversion efficiency of 0.25% was found at zero bias for the n-Ti02/p-GaP cell. Nozik further designed a new type of cell, so-called photochemical diodes that do not require external wires and functions without electrical bias [26]. This device [26], consisting of a small sandwich-like structure, Fig.7.2, such as Pt/n-GaP, and n-Ti02/p-GaP connected through ohmic contacts, when suspended in an appropriate electrolyte causes decomposition of water upon exposure to light. 

The immobilization of photoactive species into the silica-surfactant mesostructured materials is worth investigating toward future photofunctional materials. Photochemistry on solid surfaces is a growing new field which yields a wide variety of useful application such as sensitive optical media, reaction paths for controlled photochemical reactions, molecular devices for optics, etc. [17] Along this line, the incorporation of organic dyes into silica-surfactant mesostructured materials [17-20] as well as nanoporous silica films[3] have been reported so far. 

---