A Solution‐Processable meso‐Phenyl‐BODIPY‐Based n‐Channel Semiconductor with Enhanced Fluorescence Emission

Abstract

The molecular design, synthesis, and characterization of an acceptor‐donor‐acceptor (A‐D‐A) semiconductor BDY‐Ph‐2T‐Ph‐BDY comprising a central phenyl‐bithiophene‐phenyl π‐donor and BODIPY π‐acceptor end‐units is reported. The semiconductor shows an optical band gap of 2.32 eV with a highly stabilized HOMO/LUMO (−5.74 eV/−3.42 eV). Single‐crystal X‐ray diffraction (XRD) reveals D–A dihedral angle of ca. 66° and strong intermolecular “C−H ⋅⋅⋅ π (3.31 Å)” interactions. Reduced π‐donor strength, increased D–A dihedral angle, and restricted intramolecular D–A rotations allows for both good fluorescence efficiency (ΦF=0.30) and n‐channel OFET transport (μe=0.005 cm2/V ⋅ s; Ion/Ioff=104–105). This indicates a much improved (6‐fold) fluorescence quantum yield compared to the meso‐thienyl BODIPY semiconductor BDY‐4T‐BDY. Photophysical studies reveal important transitions between locally excited (LE) and twisted intramolecular charge‐transfer (TICT) states in solution and the solid state, which could be controlled by solvent polarity and nano‐aggregation. This is the first report of such high emissive characteristics for a BODIPY‐based n‐channel semiconductor.

Meso-π-Extended/Deficient BODIPYs and Low-Band-Gap Donor–Acceptor Copolymers for Organic Optoelectronics

“…When the meso-heteroaryl unit is completely removed and the alkyl chain is placed instead, a very intense fluorescence emission (Φ F = 0.95) with a small Stokes shift of ∼7 nm is observed for C11−BDY, which originates from a purely LE-dominated excited state. 55 The observed significantly red-shifted broad emission peaks, very low quantum yields, and fast decay kinetics are very different than those of characteristic BODIPY emissions. 61 These observations together clearly indicate that meso-π-extension/ deficiency facilitates CT-excited-state formation and could induce a very favorable exciton dissociation pathway in the excited state as compared with single-heteroaryl and alkyl meso-substituted BODIPYs.…”

“…The relatively stronger emission peak observed at 540 nm indicates that the LE-dominated excited state is still radiative when a single heteroaryl unit is meso attached to BODIPY, and the corresponding fluorescence quantum yield is relatively larger (Φ F = 0.05) as compared to the current meso-π-extended BODIPYs. When the meso -heteroaryl unit is completely removed and the alkyl chain is placed instead, a very intense fluorescence emission (Φ F = 0.95) with a small Stokes shift of ∼7 nm is observed for C11–BDY , which originates from a purely LE-dominated excited state . The observed significantly red-shifted broad emission peaks, very low quantum yields, and fast decay kinetics are very different than those of characteristic BODIPY emissions .…”

“…48 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) compounds were first synthesized more than five decades ago, and they have been a key building block in the last 20 years for the realization of functional molecules in fluorescence-based sensing and bioimaging applications. 55 Nonetheless, they have not played a critical role in organic photovoltaics until very recently. In the past few years, significant progress has been made in BODIPY-based D−A copolymers and their implementation in high-performance BHJ-OPVs.…”

Application progress of magnetic molecularly imprinted polymers chemical sensors in the detection of biomarkers

“…104 At present, in the determination of biomarkers, the commonly used fluorescent markers are quantum dots, 105 MOF, 106 carbon materials 58 and semiconductor nanoparticles. 107 CDs have become one of the popular fluorescent markers due to their low toxicity, good water solubility, excellent optical properties and high quantum yield. Up to now, MMIPs-FL has been used more in the detection of bovine hemoglobin (BHb), a biomarker of anemia.…”

External complexation of BODIPYs by CB[7] improves in-cell fluorescence imaging

“…Boron dipyrromethene (BODIPY) derivatives are one of the most actively studied groups of fluorophores due to their ease of synthesis, excellent photostability, and tunability of their photophysical and photochemical properties. These organic fluorophores are attracting a great deal of attention because they have been used in solar cells, 1 in photodynamic therapy (PDT), 2,3 in organic fluorescent emitting devices (OFEDs), 4,5 semiconductor, 6 bioimaging, [7][8][9] and chemo-sensors. 10 According to the Jablonski diagram, the excitation of a BODIPY chromophore leads to three competitive pathways of energy emission corresponding to different photo-functions: fluorescence emission (S1→S0 radiative decay), intersystem crossing or ISC (S1→T1 non-radiative transition), and other nonradiative decay pathways (e.g.…”