Single crystal biphenyl end-capped furan-incorporated oligomers: influence of unusual packing structure on carrier mobility and luminescence

Abstract

We report the synthesis and characterization of two new furan-based biphenyl end-capped oligomers, 2-([1,1 0 -biphenyl]-4-yl)-5-(5-([1,1 0 -biphenyl]-4-yl)thiophen-2-yl)furan (BPFT) and 5,5 0 -di([1,1 0 -biphenyl]-4-yl)-2,2 0 -bifuran (BP2F) as candidate semiconductors for organic light-emitting field effect transistors (OLETs).Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed the high thermostability of these furan-based semiconductors. X-Ray crystallography of single crystals grown by physical vapor transfer (PVT) method revealed a complicated herringbone packing of BPFT stacking with unusual flat and bent structures, which is different from that of BP2F and the bithiophene-based analogue 5,5 0 -di([1,1 0 -biphenyl]-4-yl)-2,2 0 -bithiophene (BP2T). BPFT single crystal showed a higher absolute quantum yield (51%) compared to that of BP2F and BP2T. Density Functional Theory (DFT) calculations showed that the different excitation energies between flat and bent structures led to the asymmetric transition dipoles in dark state of BPFT H-aggregates, which explains the highest PLQY of BPFT single crystal. Single crystal FET based on BPFT showed an ambipolar characteristic with high hole and electron mobilities, while single crystal FET based on BP2F exhibited p-type characteristic with a high hole mobility. Light emission was observed from the single-crystal FET based on BPFT.

Equivalent ambipolar carrier injection of electrons and holes with Au electrodes in air-stable field effect transistors

“…We present strong evidence that the Schottky limit most frequently found in organic semiconductors can be converted to the Bardeen limit by such surface modifications. A good example is given for 2,5-bis(4-biphenylyl)bithiophene 27 (BP2T, see TTC modification on a substrate was tentatively suggested earlier without any clear reasoning, 28 in the present study we will give strong evidence that the Bardeen limit can be realized from two key experiments, namely, changing metal electrodes with different u m and determining the band diagram by photoelectron yield spectroscopy (PYS). Wellbalanced ambipolar carrier injection is clearly shown and air-stable light emission from FETs is demonstrated.…”

“…The BP2T thin film (30 nm) was deposited by a vacuum vapor deposition method. 27 Thin film transistors were made by evaporating highly purified molecules under high vacuum (10 À6 Torr), and the thickness was measured in situ by a quartz crystal microbalance. The thin film deposition rate was maintained at 0.1 Å /s, and the substrate was kept at room temperature.…”

“…Light emission images were recorded using a CCD camera as reported elsewhere. 27 The drain current (I d )-drain voltage (V d ) output characteristics of an FET of BP2T polycrystalline thin films grown on TTC-SiO 2 with Au-Au homo-electrodes are shown in Fig. 2(a).…”

Unusual loss of electron mobility upon furan for thiophene substitution in a molecular semiconductor

“…The delocalization of 297 the charge on the monomer can be visualized by changes 298 in bond lengths compared to the neutral compound with 299either oxidation or reduction(Fig. 8)[26]. For 1 0 and 2 Optimized geometry, HOMO, and LUMO for 1 0 and 2 0 with a 0.02 isocontour value.…”

Development of simple hole-transporting materials for perovskite solar cells

“…[29][30][31] Second, substitution of furan for thiophene as electron-rich donor units in organic semiconductors can result in an increase in hole mobility, as demonstrated by our recent work 32 and others. 33,34 The phthalimide groups are electron-withdrawing and result in a stabilization of the frontier energy levels of HTM02 relative to HTM01, and corresponding decrease in the bandgap energy. Conveniently, solubility can be tuned using the phthalimide unit via simple modification of the alkyl chain attached to the nitrogen atom.…”