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We demonstrated the time-resolved dynamics of laser action from the conductive oligomer (CO) 1,4-Bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF). Absorption and fluorescence spectra were studied for BECV-DHF in different solvents under a wide range of concentrations. The Fourier-transform infrared spectroscopy (FTIR) spectrum was measured using simulation and experiments. The Ultraviolet-Visible (UV-VIS) spectra of the BECV-DHF were simulated in two different solutions. This CO formed a dimer and had two vibration bands in nonpolar solvents, partially dissolved in polar protic solvents, and created an H-type aggregate in polar aprotic solvents. BECV-DHF produced amplified spontaneous emission (ASE) at 464 nm in many solvents. The high efficiency of ASE is due to the waveguiding and self-assembly nature of the oligomer, which is very rare for optically pumped systems. However, BECV-DHF did not produce ASE in polar protic solvents. BECV-DHF produced ASE in both longitudinal and transverse pumping, and the full-width half maximum (FWHM) was 4 nm and 8 nm respectively for different solvents, such as toluene and acetone. The CO had a very low threshold pump energy (~0.5 mJ). The ASE efficiency was approximately 20%. The time-resolved spectroscopy (TRS) studies showed a temporal Gaussian-shaped ASE output from this CO. BECV-DHF shows remarkably high stability compare to the conjugated polymer (CP) PFO-co-pX. [ABSTRACT FROM AUTHOR]

In this work, we report on the time resolved spectroscopy of amplified spontaneous emission (ASE) from the conjugated oligomer (CO) 9,10-Bis[(9-ethyl-3-carbazoyl)-vinylenyl]-anthracene (BECVA) only upon energy transfer from another oligomer 1,4-Bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF). BECVA do not dissolve readily in tetrahydrofuran (THF) at room temperature, but completely dissolved when the temperature of the solution (THF & BECVA mix) was risen to 65 °C and remained dissolved even after cooling to room temperature. The process of heating and dissolving do not affect the performance of the CO. The heat-treated solutions were used to perform all experiments, unless mentioned. The absorption spectra indicated no aggregate formation upon increasing concentration, but the fluorescence spectra were very different for several concentrations of the solution, indicating the presence of the excimer. Pure BECVA in THF was pumped at various pump powers and concentrations. This produced only a broadband emission (from 500 to 750 nm) with a FWHM of 250 nm, which has potential applications in white light OLED. Next, we tried to produce ASE using the energy transfer process from a conjugated polymer (CP) poly (9,9-dioctylfluorenyl-2, 7-diyl) (PFO); however, this did not produce ASE, which could be due to the significant hindrance of the macromolecular PFO. The intensity of the BECVA spectra was enhanced with energy transform from PFO. The output was a broadband emission ranging from 400 to 750 nm (FWHM 350 nm). Finally, we added the oligomer BECV-DHF in solution (THF) to the BECVA solution at optimal pump power and concentration of donor (BECV-DHF), and the super-irradiant laser was produced from BECVA at 500 nm with a FWHM of 6 nm. The ultrafast dynamics of the BECVA solution under high pump power excitation and different energy donor (PFO and BECV-DHF) were extensively studied in this work. To the best of our knowledge, this is the first report of a CO that does not intrinsically produce ASE, but produces efficient ASE only via the energy transfer process by another CO. Image 10951 • ASE from the conjugated oligomer (CO) 9,10-Bis[(9-ethyl-3-carbazoyl)-vinylenyl]-anthracene (BECVA). • BECVA does not produce ASE intrinsically for different solvents in wide range of concentration. • ASE could be produce only trough energy transfer from one of the efficient CO BECV-DHF. • The energy transfer process from a macromolecule PFO to BECVA was not efficient. • The TRS studies demonstrated that BECVA begins the emission before the donor (BECV-DHF), even at low concentrations. [ABSTRACT FROM AUTHOR]

• TEM images show that oligomer covers the Perovskite Quantum dot (PQD). • Addition of oligomer enhances PQD's photochemical stability. • Oligomer improves PQD's photo-physical properties. • Oligomer/PQD colloidal blend produces a spectral narrowing under the optical cavity In this paper, we performed steady-state spectroscopy and time-resolved optical spectroscopy (TRS) of conjugated oligomer 1,4-bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF)/perovskite quantum dot (PQD) (C s P b B r 3) (LUMAR)] composites in solution. Furthermore, we investigated the lasing properties of the composites under nanosecond laser pumping. PQDs were dissolved in various solvents. These solutions were blended to form composite solutions with various weight ratios. The transmission, absorption, fluorescence, and band gap of BECV-DHF and PQDs were measured for various solvents and concentrations. Toluene was found to be the best solvent for blending PQDs and BECV-DHF. The absorption and fluorescence spectra of the blends showed the superposition of features of both materials. TEM analysis showed that the BECV-DHF and PQDs were separated by a distance of 9.75 Å. The calculated Förster radius between the BECV-DHF and PQDs was found to be approximately 50 Å – 60 Å. The presence of PQDs in the BECV-DHF solution reduces the lifetime of the excited states of BECV-DHF, and the fluorescence intensity of the PQDs precedes the fluorescence intensity of the BECV-DHF; hence, the underlying mechanism was Förster-type resonant energy transfer (FRET). The spectrally narrow peaks of PQDs and the BECV-DHF/PQDs were obtained at 523 nm using optical cavity. The spectral narrowing of the full width at half maximum (FWHM) was improved from 15 nm to 8.36 nm compared to BECV-DHF/PQDs with pure PQDs. This strategy of obtaining a short-chain stable laser material via the addition of conjugated oligomer could potentially facilitate the development of efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]