CdS/CdSe/CdS Spherical Quantum Wells with Near-Unity Biexciton Quantum Yield for Light-Emitting-Device Applications
CdS/CdSe/CdS Spherical Quantum Wells with Near-Unity Biexciton Quantum Yield for Light-Emitting-Device Applications
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DOI：
10.1021/acsmaterialslett.3c00110
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发表时间：
2023-04
影响因子：
11.4
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与零维（0D）半导体量子点相比，二维半导体纳米片（NPLs）提供了光谱窄的发光和优越的吸收系数，这使得这种几何形状成为光电应用的有吸引力的候选者。然而，基于NPLs的光学器件仍然存在多激子（MX）的非辐射俄歇衰变，这限制了MX发光、电致发光和光学增益等过程的效率。在这里，我们证明了在称为量子壳（QSs）的球形纳米片中，俄歇重组被强烈抑制，其中电荷的放松限制导致激子-激子相互作用减少。特别是，我们利用单光子计数和光子相关光谱表明，二维CdS/CdSe/CdS核/壳/壳球形量子阱达到了接近统一的双激子发射产率。螺旋钻抑制作用在螺壳直径最大的QSs中最为明显。在这些QS样品中，超长（> - 15 ns）双激子（BX）发射寿命和强激子-激子斥力的结合，使得这些样品显示出低阈值放大自发发射（ASE），大模态增益，以及在BX和MX跃迁时具有尖锐发射模式的微腔激光。最后，通过在钙钛矿基质中引入量子阱，我们在发光器件中实现了强大的电致发光增强，产生的器件亮度达到213 W/m2，最大外部量子效率提高了2.3倍。这些结果代表了实现溶液处理胶体激光器和led的重要一步。
Compared to zero-dimensional (0D) semiconductor quantum dots, 2D semiconductor nanoplatelets (NPLs) offer a spectrally narrow luminescence and superior absorption coefficients, which makes this geometry an attractive candidate for optoelectronic applications. However, optical devices based on NPLs still suffer from nonradiative Auger decay of multiple excitons (MX), which limits the efficiency of the processes, including MX luminescence, electroluminescence, and optical gain. Here, we demonstrate that Auger recombination is strongly suppressed in spherically shaped nanoplatelets, called quantum shells (QSs), where a relaxed confinement of charges leads to diminished exciton–exciton interactions. In particular, we use single photon counting and photon correlation spectroscopy to show that two-dimensional CdS/CdSe/CdS core/shell/shell spherical QSs reach near-unity biexciton emission yield. The Auger suppression was found most prominent in QSs with the largest shell diameter. A combination of ultralong (>15 ns) biexciton (BX) emission lifetimes and strong exciton–exciton repulsion in these QS samples allowed demonstrating low-threshold amplified spontaneous emission (ASE), large modal gain, and microcavity lasing featuring sharp emission modes at the BX and MX transitions. Finally, by introducing QSs within perovskite matrices, we achieved a strong electroluminescence enhancement in light-emitting devices, yielding devices as bright as 213 W/m2and a 2.3-fold enhancement of the maximum external quantum efficiency. These results represent a major step toward realizing solution-processed colloidal lasers and LEDs.