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Quasi‐2D perovskites have shown great potential in achieving solution‐processed electrically pumped laser diodes due to their multiple‐quantum‐well structure, which induces a carrier cascade process that can significantly enhance population inversion. However, continuous‐wave (CW) optically pumped lasing has yet to be achieved with near‐infrared (NIR) quasi‐2D perovskites due to the challenges in obtaining high‐quality quasi‐2D films with suitable phase distribution and morphology. This study regulates the crystallization of a NIR quasi‐2D perovskite ((NMA)2FAn−1PbnI3n+1) using an 18‐crown‐6 additive, resulting in a compact and smooth film with a largely improved carrier cascade efficiency. The amplified spontaneous emission threshold of the film is reduced from 47.2 to 35.9 µJ cm−2. Furthermore, by combining the film with a high‐quality distributed feedback grating, this study successfully realizes a CW NIR laser of 809 nm at 110 K, with a high Q‐factor of 4794 and a low threshold of 911.6 W cm−2. These findings provide an important foundation for achieving electrically pumped laser diodes based on the unique quasi‐2D perovskites. [ABSTRACT FROM AUTHOR]

The external quantum efficiency (EQE) of state‐of‐the‐art near‐infrared perovskite light‐emitting diodes (PeLEDs) is now approaching the limit set by the out‐coupling efficiency. However, there is plenty of room for enhancing these devices' radiance and the EQE roll‐off. This work reports how conductive and passivating additives construct efficient high‐radiance near‐infrared PeLEDs with improved EQE roll‐off. Specifically, the synergistic effect of 1,4‐phenylenediacetic acid (PDA) and 5‐aminovaleric acid (5‐AVA) is used to regulate the quality of the perovskite emissive layer, thereby enhancing the roll‐off threshold of injection currents (a value at which the device EQE or radiance starts degrading). According to in situ structural evolution analyses from the perovskite precursor to the perovskite crystal, the presence of PDA within the perovskite precursor solution can produce an intermediate phase with 5‐AVA and formanmidinium cation, which can retard the perovskite nucleation and crystal growth, leading to improved perovskite film quality. The resulting champion PeLED delivers among the highest radiance of 505 W sr−1 m−2 and a peak EQE of 17.56%. More importantly, the improved PeLED shows a well‐retained radiance of 80% at a current injection density of up to ≈1800 mA cm−1, opening a new avenue for high‐radiance PeLEDs with improved roll‐off degradation. [ABSTRACT FROM AUTHOR]