Flexible, Free-Standing Polymer Membranes Sensitized by CsPbX3 Nanocrystals as Gain Media for Low Threshold, Multicolor Light Amplification

Abstract

Lead halide perovskite nanocrystals (NCs) are highly suitable active media for solution-processed lasers in the visible spectrum, owing to the wide tunability of their emission from blue to red via facile ion-exchange reactions. Their outstanding optical gain properties and the suppressed nonradiative recombination losses stem from their defecttolerant nature. In this work, we demonstrate flexible waveguides combining the transparent, bioplastic, polymer cellulose acetate with green CsPbBr 3 or red-emitting CsPb(Br,I) 3 NCs in simple solutionprocessed architectures based on polymer-NC multilayers deposited on polymer micro-slabs. Experiments and simulations indicate that the employment of the thin, free-standing membranes results in confined electrical fields, enhanced by 2 orders of magnitude compared to identical multilayer stacks deposited on conventional, rigid quartz substrates. As a result, the polymer structures exhibit improved amplified emission characteristics under nanosecond excitation, with amplified spontaneous emission (ASE) thresholds down to ∼95 μJ cm −2 and ∼70 μJ cm −2 and high net modal gain up to ∼450 and ∼630 cm −1 in the green and red parts of the spectrum, respectively. The optimized gain properties are accompanied by a notable improvement of the ASE operational stability due to the low thermal resistance of the substrate-less membranes and the intimate thermal contact between the polymer and the NCs. Their application potential is further highlighted by the membrane's ability to sustain dual-color ASE in the green and red parts of the spectrum through excitation by a single UV source, activate underwater stimulated emission, and operate as efficient white light downconverters of commercial blue LEDs, producing high-quality white light emission, 115% of the NTSC color gamut.

Colloidal Semiconductor Nanocrystal Lasers and Laser Diodes

“…These include vertical cavity surface emitting lasers (VCSELs), ,, devices based on whispering gallery mode structures, ,, and lasers employing Fabry–Pérot resonators . An interesting recent study described in ref demonstrated ASE-active waveguides prepared as free-standing, flexible, water-resistant membranes composed of functionalized perovskite nanocrystals and a cellulose acetate polymer.…”

Strong Light–Matter Coupling in Lead Halide Perovskite Quantum Dot Solids

“…Third, QDs may suffer from spectral diffusion, which causes fluctuations in the electronic energy transitions . In this context, recent advances to improve the quality of colloidal PQDs have permitted to attain transparent films made from cubic CsPbBr 3 nanocrystals, which have been integrated into a photonic crystal resonator to observe weak light–matter coupling properties, as evidenced by the observation of amplified spontaneous emission. , In another recent achievement, it has been shown that PQD films, whose absorption spectra partially preserve the excitonic features present in the colloidal cubic CsPbBr 3 nanocrystals used as building blocks, exhibit the excitonic optical Stark effect under very intense photoexcitation . Both results imply substantial advancement in the field of perovskite photonics.…”

Simultaneous Dual‐Color Amplified Spontaneous Emission and Lasing from Colloidal Quantum Well Gain Media in their Own Layered Waveguide and Cavity

“…[ 10,11 ] To date, several systems of fluorescent semiconductor nanomaterials and deposition techniques have been investigated as part of the efforts to demonstrate efficient and stable multicolor lasers. Among them, group III‐V quantum wells using epitaxial growth, [ 12 ] group II‐VI semiconductors using chemical vapor deposition (CVD), [ 13 ] and colloidal perovskites, [ 14 ] and organic molecules [ 15 ] using spin‐casting have been employed as the active media for the demonstration of multi‐wavelength optical gain and lasing. To achieve the lasing at two or more different wavelengths simultaneously, different types of optical cavities such as distributed‐feedback (DFB) cavity, [ 16 ] whispering‐gallery‐mode (WGM) cavity, [ 17 ] and nanowire [ 6 ] and nanosheet [ 18 ] self‐resonant cavities have been implemented.…”