A New Generation of Liquid Lasers from Engineered Semiconductor Nanocrystals with Giant Optical Gain

Abstract

With the development of optofluidic technology, liquid lasers have attracted intense interest but still face a formidable challenge due to the lack of qualified gain media and creative device design. Compared to the organic fluorescent dyes and traditional CdSe‐based nanocrystals (NCs), the lead‐halide perovskite (LHP) NCs feature larger gain coefficient and higher robustness, which renders LHP NCs a promising unexploited liquid gain medium. Herein, for the first time, the hidden principle governing the solution‐based light amplification in LHP semiconductor NCs is demystified and it is demonstrated that the LHP NCs are superior solution‐phase gain media showing a giant (≈2600 cm−1) optical gain. On this basis, a novel microfluidic laser device is designed and realized that exhibits a record‐low pump threshold (≈22.7 µJ cm−2), high Q‐factor (≈7480), large output polarization (≈0.91), and long‐time robustness over high‐intensity operation, which is readily applicable to practical applications. The findings represent a significant step toward the technologically important liquid lasers of the new generation and can advance optofluidic applications.

Slowing Down the Hot Carrier Relaxation Dynamics of CsPbX3 Nanocrystals by the Surface Passivation Strategy

“…All inorganic lead halide perovskites (LHPs), CsPbX 3 (X = Cl/Br/I), have attracted attention as one of the most affordable emitters with promising performance in several optoelectronic applications such as light-emitting diodes, photodetectors, lasers, etc. − Exceptional characteristic features, essentially a wide absorption cross-section, tuneable band gap, long carrier lifetime, high photoluminescence quantum yields (PLQYs), and excellent charge transport properties of CsPbX 3 , are largely responsible for their performance in optoelectronic applications. − The operation of optoelectronic devices is strongly dependent on the dynamics of the photo-excited charge carriers, which influences various ultrafast processes, such as hot carrier (HC) relaxation, carrier recombination, and ultrafast carrier transfer dynamics. , Generation of carriers above the conduction band by excitation energy larger than the band gap of the semiconductor leads to the formation of HCs with a temperature higher than the lattice temperature. The rapid cooling (in sub-ps time) of these HCs to the band-edge through the loss of their excess energy through carrier–carrier scattering and carrier–phonon scattering is a major energy loss channel. − Hence, the mitigation of heat energy losses through the extraction of the HCs before cooling in the band-edge enables to achieve the power conversion efficiency beyond the Shockley Queisser limit. ,, Therefore, delaying the HC relaxation time is an essential task before we design efficient photovoltaic devices.…”

Dual-Optical Signal Molecular Logic System Based on CsPbBr3@SiO2 Film Electrodes with Modulated Photoluminescence and Electrochemiluminescence Behaviors

“…Due to the unavoidable slight aggregation of CsPbBr 3 @SiO 2 NCs in aqueous solution, the UV−vis extinction peaks for both dispersion and films demonstrated somehow scattering, different from what was obtained in organic solvents. 50 In spite of this, the results of the CsPbBr 3 @SiO 2 films were essentially consistent with those of the UV−vis and PL for the CsPbBr 3 @SiO 2 NC dispersion in aqueous solution (Figure 1A), indicating that the CsPbBr 3 @ SiO 2 films maintained the same properties as the CsPbBr 3 @ SiO 2 NCs. The ECL spectra of CsPbBr 3 @SiO 2 films at the anode with an onset of approximately +0.75 V reached a maximum emission of approximately +1.04 V in a buffer solution containing 10 mM DBAE as a coreactant (Figure 1C).…”

“…Green fluorescence was emitted from the films under UV light (Figure B, inset) with the maximum emission peak at 523 nm (excitation wavelength of 365 nm), and the maximum UV–vis extinction was observed at 521 nm. Due to the unavoidable slight aggregation of CsPbBr 3 @SiO 2 NCs in aqueous solution, the UV–vis extinction peaks for both dispersion and films demonstrated somehow scattering, different from what was obtained in organic solvents . In spite of this, the results of the CsPbBr 3 @SiO 2 films were essentially consistent with those of the UV–vis and PL for the CsPbBr 3 @SiO 2 NC dispersion in aqueous solution (Figure A), indicating that the CsPbBr 3 @SiO 2 films maintained the same properties as the CsPbBr 3 @SiO 2 NCs.…”

Two‐Color Amplified Spontaneous Emission from Auger‐Suppressed Quantum Dots in Liquids

“…[2] However, there is considerable need for QDbased liquid optical gain media. [20][21][22][23][24] In particular, they could serve as a replacement for existing laser dyes. In addition to improved photostability, they can, in principle, enable a greater optical gain bandwidth in combination with facile, wide-range spectral tunability of the central wavelength.…”