(Dibenzoylmethanato)boron Difluoride Derivatives Containing Triphenylamine Moieties: A New Type of Electron‐Donor/π‐Acceptor System for Dye‐Sensitized Solar Cells

Abstract

(Dibenzoylmethanato)boron difluoride derivatives containing triphenylamine moieties were synthesized as a new type of electron-donor/π-acceptor system. These new compounds exhibited long-wavelength absorptions in the UV/Vis spectra, and reversible oxidation and reduction waves in cyclic voltammetry experiments. Their amphoteric redox properties are based on their resonance hybrid forms, in which a positive charge is delocalized on the triphenylamine moieties and a negative charge is localized on the boron atoms. Molecular orbital (MO) calculations indicate that their HOMO and LUMO energies vary with the number of phenylene rings connected to the difluoroboron-chelating ring. This is useful for optimizing the HOMO and LUMO levels to an iodine redox (I(-)/I3(-)) potential and a titanium dioxide conduction band, respectively. Dye-sensitized solar cells fabricated by using these compounds as dye sensitizers exhibited solar-to-electric power conversion efficiencies of 2.7-4.4 % under AM 1.5 solar light.

New Fluorescence Domain “Excited Multimer” Formed upon Photoexcitation of Continuously Stacked Diaroylmethanatoboron Difluoride Molecules with Fused π‐Orbitals in Crystals

“…Among the substancesi nt his family,d ibenzoylmethanatoborond ifluoride (P1 BF 2 ,S cheme 1) is an especially interesting compound from the viewpoint of probing relationshipsb etween aggregation mode and FL properties. [23][24][25][26][27][28][29][30][31][32][33][34][35] Since the report by Mirochnik and co-workers showing that P1 BF 2 FL involves emission from arrays of molecules in crystalsi nw hich intermolecularo rbital interactions occur, [30][31][32][33][34][35] many others have observed that P1 BF 2 derivatives exhibit interesting molecular aggregation-based emissionp henomena such as mechanofluorochromism, [36][37][38][39] aggregation-induced emission (AIE), [40] and room-temperature phosphorescence. [41,42] Guided by thesee arlier efforts, we carriedo ut an investigation aimed at elucidating the FL properties and crystal-packing structures of 1BF 2 derivatives.…”

Phosphorescence Tuning through Heavy Atom Placement in Unsymmetrical Difluoroboron β‐Diketonate Materials

“…The quantum yields of piperidyl‐substituted phenyl systems 5 and 6 in CH 2 Cl 2 are about 1.0 % and 2.8 % respectively. The low quantum yields of 5 and 6 are presumably correlated to strong CT character in the transition, which permits large, energy‐dissipating nuclear reorganization …”

Pyridomethene–BF2 complex/phenothiazine hybrid sensitizer with high molar extinction coefficient for efficient, sensitized solar cells

“…One of the main shortcomings of metal complex dyes is their weak absorption in the red region of visible spectrum. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] In our earlier report, we have designed a different pyridomethene-BF 2 complex, with a similar structure to BODIPY, that exhibited a very large extinction coefficient (ε>5×10 4 M -1 cm -1 ). A high absorption coefficient in the visible wavelength will increase the value of shortcircuit current density (J sc ).…”