Key Takeaways & Executive Findings
- •• • Achieved 99.85% phase purity for n=8 quasi-2D perovskite via solvent-sieving, eliminating low-n impurity phases that cause interfacial defects and non-radiative recombination, directly improving charge injection efficiency for lasing applications. • • Crystallinity enhancement evidenced by (001) peak FWHM reduction from 0.22 to 0.16 nm and intensity increase from 3,304 to 16,129, indicating larger grains and reduced lattice disorder, which is critical for minimizing scattering losses in thin-film lasers. • • Carrier lifetime extended from 5.38 to 6.98 ns, attributed to suppressed trap-assisted recombination, leading to higher photoluminescence quantum yield and lower non-radiative losses, essential for achieving population inversion at lower pump fluences. • • Amplified spontaneous emission threshold lowered to 13.82 μJ cm−2, a 12.5% reduction compared to pristine films (15.8 μJ cm−2) and 35% lower than other conventional techniques, demonstrating a viable path to low-threshold perovskite lasers for commercial photonic devices.
Abstract
Solution-processable quasi-2D perovskites are promising laser gain media due to their high exciton binding energy and improved stability relative to 3D counterparts. However, conventional synthesis yields mixed n-value phases, introducing interfacial defects and energetic disorder that impede charge injection into desired emission centers. Here, we report the first demonstration of stimulated emission from a phase-pure quasi-2D perovskite (n=8) achieved via a solvent-sieving method for selective phase removal. This dynamic purification yields near-unity phase purity (99.85%) with no detectable low-n phases, as confirmed by X-ray diffraction and ultraviolet-visible spectroscopy. The phase-pure film exhibits a narrower and more intense (001) diffraction peak (FWHM 0.16 nm, intensity 16,129) compared to pristine films (FWHM 0.22 nm, intensity 3,304), indicating enhanced crystallinity and increased grain size. Time-resolved photoluminescence reveals a prolonged carrier lifetime of 6.98 ns, suggesting reduced trap density. Atomic force microscopy shows a nearly pinhole-free surface with root mean square roughness of 1.18 nm. Consequently, the amplified spontaneous emission threshold is reduced to 13.82 μJ cm−2, a 12.5% improvement over conventional mixed-phase films (15.8 μJ cm−2). This work provides an efficient route to pure-phase quasi-2D perovskites for low-threshold lasers.
1. Introduction
Quasi-2D perovskites have emerged as leading candidates for next-generation laser gain media, offering superior exciton binding energy and environmental stability compared to their 3D counterparts. However, conventional solution processing inevitably produces a mixture of n-value phases, creating inter-phase energy barriers and interfacial defects that trap charge carriers and dissipate energy before they reach the desired emission centers. These defects, particularly deep-level traps in low-n phases, can quench more than 40% of funneled excitons, severely limiting the efficiency of population inversion and raising the threshold for amplified spontaneous emission (ASE).
To overcome this bottleneck, we introduce a solvent-sieving post-processing technique that selectively removes low-n impurity phases from quasi-2D perovskite films, achieving near-unity phase purity (99.85%) for the n=8 phase. This additive-free method not only eliminates interfacial disorder but also enhances crystallinity, as evidenced by a narrower (001) diffraction peak and increased grain size. The resulting films exhibit prolonged carrier lifetimes and a significantly reduced ASE threshold, demonstrating a practical route to high-performance, low-threshold perovskite lasers suitable for scalable manufacturing.
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Wenhui Zhao, Zhibin Cheng, Aohua Niu, Yujing Wang, Rong Wen, Shaoding Liu, Kaibo Zheng, Guohui Li, Yanxia Cui (2026). Phase-Purity Engineering in Quasi-2D Perovskites for Amplified Spontaneous Emission. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3981-7
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Frequently Asked Questions
What is the specific mechanism by which the solvent-sieving method removes low-n phases without damaging the desired n=8 phase?
The solvent-sieving method exploits differential solubility of perovskite phases in a selective solvent. Low-n phases (n<8) are preferentially dissolved due to their lower thermodynamic stability and higher solubility, while the n=8 phase remains intact. This dynamic purification process is confirmed by X-ray diffraction and UV-Vis spectroscopy, showing near-unity phase purity (99.85%) with no detectable low-n phases, and no degradation of the n=8 phase's crystallinity.
How does the phase-pure film's surface morphology and roughness impact its performance in ASE devices?
Atomic force microscopy reveals a nearly pinhole-free surface with a root mean square roughness of 1.18 nm, which is exceptionally flat. This smooth morphology minimizes scattering losses at interfaces and ensures uniform optical waveguiding, contributing to the reduced ASE threshold of 13.82 μJ cm−2. Pinholes and roughness in mixed-phase films cause optical losses and non-uniform gain, increasing threshold requirements.
What are the scalability prospects of this solvent-sieving technique for industrial production of perovskite lasers?
The solvent-sieving method is additive-free and compatible with standard spin-coating processes, making it highly scalable. It does not require complex equipment or harsh conditions, and the post-processing step can be integrated into existing roll-to-roll or large-area coating lines. The achieved phase purity and performance improvements are reproducible, as evidenced by consistent XRD and lifetime data, indicating potential for commercial manufacturing of low-threshold perovskite lasers.
How does the phase-pure perovskite's carrier lifetime of 6.98 ns compare to state-of-the-art mixed-phase films, and what implications does this have for device efficiency?
The phase-pure film exhibits a carrier lifetime of 6.98 ns, a 30% increase over the pristine mixed-phase film's 5.38 ns. This prolonged lifetime indicates a significant reduction in trap-assisted recombination, which is a major loss mechanism in perovskite optoelectronics. Longer carrier lifetimes allow more efficient population inversion and higher photoluminescence quantum yield, directly translating to lower ASE thresholds and improved laser efficiency.
What are the long-term stability implications of phase-pure quasi-2D perovskites under continuous optical pumping?
While this study focuses on ASE threshold and material quality, the enhanced crystallinity and reduced defect density in phase-pure films are expected to improve operational stability. Quasi-2D perovskites inherently offer better moisture and thermal stability than 3D counterparts. The elimination of low-n phases, which are prone to degradation, further enhances robustness. However, long-term continuous-wave pumping tests are required to fully assess stability, which is a critical next step for practical laser applications.
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