PubMed İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/397
Browse
5 results
Search Results
Article Citation - WoS: 25Citation - Scopus: 25Self-Resonant Microlasers of Colloidal Quantum Wells Constructed by Direct Deep Patterning(Amer Chemical Soc, 2021-05-24) Gheshlaghi, Negar; Foroutan-Barenji, Sina; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Humayun, Muhammad Hamza; Demir, Hilmi VolkanHere, the first account of self-resonant fully colloidal mu-lasers made from colloidal quantum well (CQW) solution is reported. A deep patterning technique is developed to fabricate well-defined high aspect-ratio on-chip CQW resonators made of grating waveguides and in-plane reflectors. The fabricated waveguide-coupled laser, enabling tight optical confinement, assures in-plane lasing. CQWs of the patterned layers are closed-packed with sharp edges and residual-free lifted-off surfaces. Additionally, the method is successfully applied to various nanoparticles including colloidal quantum dots and metal nanoparticles. It is observed that the patterning process does not affect the nanocrystals (NCs) immobilized in the attained patterns and the different physical and chemical properties of the NCs remain pristine. Thanks to the deep patterning capability of the proposed method, patterns of NCs with subwavelength lateral feature sizes and micron-scale heights can possibly be fabricated in high aspect ratios.Article Citation - WoS: 128Citation - Scopus: 136Record 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, 2019-12-23) Liu, Baiquan; Altintas, Yemliha; Wang, Lin; Shendre, Sushant; Sharma, Manoj; Sun, Handong; Demir, Hilmi VolkanColloidal 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.Article Citation - WoS: 11Citation - Scopus: 12Optical Gain in Ultrathin Self-Assembled Bi-Layers of Colloidal Quantum Wells Enabled by the Mode Confinement in Their High-Index Dielectric Waveguides(Wiley-VCH Verlag GmbH, 2020-10-20) Foroutan-Barenji, Sina; Erdem, Onur; Gheshlaghi, Negar; Altintas, Yemliha; Demir, Hilmi VolkanThis study demonstrates an ultra-thin colloidal gain medium consisting of bi-layers of colloidal quantum wells (CQWs) with a total film thickness of 14 nm integrated with high-index dielectrics. To achieve optical gain from such an ultra-thin nanocrystal film, hybrid waveguide structures partly composed of self-assembled layers of CQWs and partly high-index dielectric material are developed and shown: in asymmetric waveguide architecture employing one thin film of dielectric underneath CQWs and in the case of quasi-symmetric waveguide with a pair of dielectric films sandwiching CQWs. Numerical modeling indicates that the modal confinement factor of ultra-thin CQW films is enhanced in the presence of the adjacent dielectric layers significantly. The active slabs of these CQW monolayers in the proposed waveguide structure are constructed with great care to obtain near-unity surface coverage, which increases the density of active particles, and to reduce the surface roughness to sub-nm scale, which decreases the scattering losses. The excitation and propagation of amplified spontaneous emission (ASE) along these active waveguides are experimentally demonstrated and numerically analyzed. The findings of this work offer possibilities for the realization of ultra-thin electrically driven colloidal laser devices, providing critical advantages including single-mode lasing and high electrical conduction.Article Citation - WoS: 101Citation - Scopus: 104Giant Alloyed Hot Injection Shells Enable Ultralow Optical Gain Threshold in Colloidal Quantum Wells(Amer Chemical Soc, 2019-08-22) Altintas, Yemliha; Gungor, Kivanc; Gao, Yuan; Sak, Mustafa; Quliyeva, Ulviyya; Bappi, Golam; Demir, Hilmi VolkanAs an attractive materials system for high- Record-low optical gain threshold in giant-shell COWs performance optoelectronics, colloidal nanoplatelets (NPLs) benefit from atomic-level precision in thickness, minimizing emission inhomogeneous broadening. Much progress has been made to enhance their photoluminescence quantum yield (PLQY) and photostability. However, to date, layer-by-layer growth of shells at room temperature has resulted in defects that limit PLQY and thus curtail the 0.2 performance of NPLs as an optical gain medium. Here, we introduce a hot-injection method growing giant alloyed shells using an approach that reduces core/shell lattice mismatch and suppresses Auger recombination. Near-unity PLQY is achieved with a narrow full-width-at-half-maximum (20 nm), accompanied by emission tunability (from 610 to 650 nm). The biexciton lifetime exceeds 1 ns, an order of magnitude longer than in conventional colloidal quantum dots (CQDs). Reduced Auger recombination enables record-low amplified spontaneous emission threshold of 2.4 mu J cm(-2) under one-photon pumping. This is lower by a factor of 2.5 than the best previously reported value in nanocrystals (6 /kJ cm(-2) for CdSe/CdS NPLs). Here, we also report single-mode lasing operation with a 0.55 mu J cm(-2) threshold under two-photoexcitation, which is also the best among nanocrystals (compared to 0.76 mu J cm(-2) from CdSe/CdS CQDs in the Fabry-Perot cavity). These findings indicate that hot-injection growth of thick alloyed shells makes ultrahigh performance NPLs.Article Citation - WoS: 34Citation - Scopus: 33Deep-Red Colloidal Quantum Well Light-Emitting Diodes Enabled Through a Complex Design of Core/Crown Shell Heterostructure(Wiley-VCH Verlag GmbH, 2021-12-10) Shabani, Farzan; Dehghanpour Baruj, Hamed; Yurdakul, Iklim; Delikanli, Savas; Gheshlaghi, Negar; Isik, Furkan; Demir, Hilmi VolkanExtending 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.