Browsing by Subject "Hot injection"

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    Deep-red-emitting colloidal quantum well light-emitting diodes enabled through a complex design of core/crown/double shell heterostructure
    (Wiley, 2022-02-24) Shabani, Farzan; Dehghanpour Baruj, Hamed; Yurdakul, Iklim; Delikanlı, Savaş; Gheshlaghi, Negar; Işık, Furkan; Liu, B.; Altıntaş, Yemliha; Canımkurbey, Betül; Demir, Hilmi Volkan
    Extending the emission peak wavelength of quasi-2D colloidal quantum wells has been an important quest to fully exploit the potential of these materials, which has not been possible due to the complications arising from the partial dissolution and recrystallization during growth to date. Here, the synthetic pathway of (CdSe/CdS)@(1-4 CdS/CdZnS) (core/crown)@(colloidal atomic layer deposition shell/hot injection shell) hetero-nanoplatelets (NPLs) using multiple techniques, which together enable highly efficient emission beyond 700 nm in the deep-red region, is proposed and demonstrated. Given the challenges of using conventional hot injection procedure, a method that allows to obtain sufficiently thick and passivated NPLs as the seeds is developed. Consequently, through the final hot injection shell coating, thick NPLs with superior optical properties including a high photoluminescence quantum yield of 88% are achieved. These NPLs emitting at 701 nm exhibit a full-width-at-half-maximum of 26 nm, enabled by the successfully maintained quasi-2D shape and minimum defects of the resulting heterostructure. The deep-red light-emitting diode (LED) device fabricated with these NPLs has shown to yield a high external quantum efficiency of 6.8% at 701 nm, which is on par with other types of LEDs in this spectral range. © 2021 Wiley-VCH GmbH
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    ItemOpen Access
    Record high external quantum efficiency of 19.2% achieved in light-emitting diodes of colloidal quantum wells enabled by hot-Injection shell growth
    (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2020) Liu, B.; Altıntaş, Yemliha; Wang, L.; Shendre, S.; Sharma, Manoj; Sun, H.; Mutlugün, Evren; Demir, Hilmi Volkan
    Colloidal quantum wells (CQWs) are regarded as a highly promising class of optoelectronic materials, thanks to their unique excitonic characteristics of high extinction coefficients and ultranarrow emission bandwidths. Although the exploration of CQWs in light‐emitting diodes (LEDs) is impressive, the performance of CQW‐LEDs lags far behind other types of soft‐material LEDs (e.g., organic LEDs, colloidal‐quantum‐dot LEDs, and perovskite LEDs). Herein, high‐efficiency CQW‐LEDs reaching close to the theoretical limit are reported. A key factor for this high performance is the exploitation of hot‐injection shell (HIS) growth of CQWs, which enables a near‐unity photoluminescence quantum yield (PLQY), reduces nonradiative channels, ensures smooth films, and enhances the stability. Remarkably, the PLQY remains 95% in solution and 87% in film despite rigorous cleaning. Through systematically understanding their shape‐, composition‐, and device‐engineering, the CQW‐LEDs using CdSe/Cd0.25Zn0.75S core/HIS CQWs exhibit a maximum external quantum efficiency of 19.2%. Additionally, a high luminance of 23 490 cd m−2, extremely saturated red color with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.715, 0.283), and stable emission are obtained. The findings indicate that HIS‐grown CQWs enable high‐performance solution‐processed LEDs, which may pave the path for future CQW‐based display and lighting technologies.