Organic salt photovoltaics

Abstract

A review of organic salt based photovoltaics highlighting unique and ionic properties for organic and transparent photovoltaics, including deep NIR absorption and independently tunable molecular orbitals.

Recent advances with optical upconverters made from all-organic and hybrid materials

“…An interesting class of NIR dyes for further investigation is cyanines. Cyanine dyes are synthetically relatively easy accessible, have very high light extinction coefficients and good filmforming properties [71]. Thin films of heptamethine cyanines appear almost colour free in the visible and have been used, e.g., for the fabrication of transparent solar cells and photodetectors [72][73][74].…”

Superweak Coordinating Anion as Superstrong Enhancer of Cyanine Organic Semiconductor Properties

“…[52] However both J SC and FF are driven to their maximum for the Cy5 chromophore when [Al(pftb) 4 ] À is employed and approach the higher limit values for the FF found in organic semiconductors. [31,53] In case of Cy5[Al(pftb) 4 ] the J sc thrives also due to the increased active light absorbing layer thickness of 15 nm and increased number of monomeric species within the amorphous film by reduction of aggregate formation visible from the solid state UV-Vis spectrum (Figure 2A, B).…”

“…[25,26] Considering the structural properties of cyanine dyes it becomes clear why the counterion has such a tremendous influence on the chromophore's electronic, conformational and optical properties; especially in neat spincasted films and organic electronic devices. [24,[27][28][29][30][31][32][33] positive charge of the chromophore in its ground state electron configuration is compensated by the anion. On the contrary, exciting a cyanine and transferring an electron to an acceptor in an OPV device creates formally a doubly positively charged molecule for a short period, a highly unfavourable state for the cyanine chromophore when considering the standard ionisation potential approach for molecules.…”

Physical vapour deposition of cyanine salts and their first application in organic electronic devices

“…[17][18][19] Since their discovery in 1856 20 cyanine dyes were used in various applications, according to the scientific interest in each decade starting from photography, 20 CD-R based data storage, [21][22][23][24] life science, 25,26 non-linear optics 27,28 and organic photovoltaics (OPV) or photodiodes. 17,[29][30][31][32][33][34][35][36][37][38][39] While neutral organic semiconductors can be easily evaporated mainly due to the weak intermolecular van der Waals forces, ionic organic functional materials such as cyanine dyes suffer from strong Coulomb interactions which results in high melting points and decomposition at ambient temperatures. 40,41 Heteroatoms in the polymethine chain or in aromatic moieties as well as high molecular weight of the cyanine salts and counterions with localised charge induce additional decomposition pathways when thermal stress is applied.…”