Wide-gamut lasing from a single organic chromophore

Abstract

The development of wideband lasing media has deep implications for imaging, sensing, and display technologies. We show that a single chromophore can be engineered to feature wide-gamut fluorescence and lasing throughout the entire visible spectrum and beyond. This exceptional color tuning demonstrates a chemically controlled paradigm for light emission applications with precise color management. Achieving such extensive color control requires a molecular blueprint that yields a high quantum efficiency and a high solubility in a wide variety of liquids and solids while featuring a heterocyclic structure with good steric access to the lone pair electrons. With these requirements in mind, we designed a lasing chromophore that encloses a lasing color space twice as large as the sRGB benchmark. This record degree of color tuning can in principle be adapted to the solid state by incorporating the chromophore into polymer films. By appropriately engineering the base molecular structure, the widest range of lasing wavelengths observed for a conventional gain medium can be achieved, in turn establishing a possible route toward high-efficiency light emitters and lasers with near-perfect chromaticity.

Fig. 1. Molecular sketches.

Chemical structures of a DSB (PPV), b P2VB, and c Np-P4VB. The key change between DSB and P2VB is the pyridine ring on each end. The difference between the P2VB and P4VB structures is the position of the nitrogen in the pyridine rings. The Np-P4VB synthesized here is similar to P4VB but with the addition of branched neopentyloxy groups on the central benzene ring

Fig. 2. Color photograph of solutions.

Photograph of the Np-P4VB chromophore (2 mM except 0.7 mM in cyclohexane) in solution taken under a black light a dissolved in cyclohexane (blue); b dissolved in DMF (teal); c dissolved in DMF with the addition of Zn(NO₃)₂ (green); d dissolved in DMF with the addition of Hg(NO₃)₂ (yellow); and e dissolved in acidified DMF (red–orange)

Fig. 3. Fluorescence and absorption spectra.

Absorption (dashed) and photoluminescence (solid) spectra of Np-P4VB in a cyclohexane, b pure DMF, c DMF with 500 mM Zn(NO₃)₂, d DMF saturated (~100 mM) with Hg(NO₃)₂, and e DMF with 500 mM HCl. The concentration of the chromophore for absorption measurements was 0.1 mM, while that for PL measurements was 2 mM (0.7 mM for cyclohexane). The insets show photographs of the luminescence corresponding to the spectrum for each panel

Fig. 4. Fluorescence and lasing data.

a Lifetimes of pure, HCl (acid)-doped, and Zn(NO₃)₂-doped solutions of Np-P4VB (3 mM). b Output pulse power for various concentrations of Np-P4VB in DMF. c Threshold behavior of a 2 mM solution of Np-P4VB in DMF when stimulated at 337 nm by an N₂ laser. The inset shows a double-slit interference pattern from the laser emission. d–g show the Np-P4VB laser emission wavelengths for the blue (0.7 mM Np-P4VB in cyclohexane), teal (2 mM Np-P4VB in DMF), green (2 mM Np-P4VB/DMF with 500 mM Zn(NO₃)₂), and red lasing (2 mM Np-P4VB/DMF with 0.1 M HCl) solutions

Fig. 5. Lasing color range.

a Lasing wavelengths for Np-P4VB in DMF achievable by tuning the laser cavity. The lasing intensity was normalized across the different groups for ease of visualization. b CIE 1931 chromaticity diagram showing the achievable color space from the Np-P4VB laser tuned optimally for 442, 514, and 695 nm, compared with the (Adobe) wide-gamut RGB and the standard RGB color spaces. The unitless x and y axes are defined as usual in the CIE system

Fig. 6. Photograph (raw unprocessed data) of red–orange, yellow–green, teal, and white polyelectrolyte bilayer films containing dissolved Np-P4VB.

A hand-held overhead blacklight was used for excitation. The corresponding PL spectra are shown in Fig. S8. The wafers are 1 cm in diameter

Fig. 7. Scheme showing the intermediate products during the synthesis of Np-P4VB.

The products are numbered according to the step of the synthetic route. Step 4 shows the Wittig–Horner-type reaction, which produces Np-P4VB

Fig. 8. Simplified diagram of the laser cavity set-up.

Cuvette #1 is placed in the tunable lasing cavity and is excited with 337-nm pulses from a nitrogen laser. The lasing output is directed through cuvette #2 for further amplification before entering the spectroscopy system