Apurba De

Bio: Apurba De is an academic researcher from University of Hyderabad. The author has contributed to research in topics: Perovskite (structure) & Photoluminescence. The author has an hindex of 11, co-authored 17 publications receiving 715 citations.

State of the Art and Prospects for Halide Perovskite Nanocrystals.

Abstract: Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.

Achieving Near-Unity Photoluminescence Efficiency for Blue-Violet-Emitting Perovskite Nanocrystals

Abstract: While perovskite nanocrystals (NCs) have shown great promise as materials for efficient light-emitting diodes (LEDs), low photoluminescence quantum yield (PLQY) of the blue-emitting perovskites is an impediment to the development of white LEDs of which blue is an essential component. Herein, we report that room temperature postsynthetic treatment of weakly blue-violet-emitting (PLQY 3%) CsPbCl3 NCs with CdCl2 results in an instantaneous enhancement of the PLQY to near-unity without affecting the PL peak position (406 nm) and spectral width. The time-resolved PL and ultrafast transient absorption measurements confirm the removal of nonradiative defect states of the CsPbCl3 NCs in treated sample. The elemental composition and structural data of the treated sample reveal facile doping of Cd2+ into the crystal lattice without affecting the size and shape of the NCs. Extraordinary PLQY, high air stability and photostability and ease of preparation of this Cd-doped CsPbCl3 make it by far the most attractive blu...

Tackling the Defects, Stability, and Photoluminescence of CsPbX3 Perovskite Nanocrystals

Abstract: Defects have always been an integral part of semiconductor crystals, controlling their optical and electronic properties. Even though growing popularity of the CsPbX3 (X = Cl, Br, I, and their mixt...

Luminescence tuning and exciton dynamics of Mn-doped CsPbCl3 nanocrystals.

Abstract: Mn-Doped perovskite nanocrystals (NCs) are a new class of materials offering exciting opportunities to control over their optical and magnetic properties. Herein, we report a series of Mn-doped CsPbCl3 NCs exhibiting a tunable Mn photoluminescence (PL) band with a PL peak wavelength pushed up to 625 nm and tuned over a range of 40 nm, the largest achieved so far, by only varying the Mn content. The X-band EPR data and Mn PL decay behaviour of the NCs reveal that the exchange interaction between Mn2+ ions is mainly responsible for a large shift of the Mn PL band. Ultrafast pump–probe measurements show that exciton–dopant energy transfer in these NCs is slower (∼50–100 ps) than trapping of the carriers (∼8–10 ps) in the host lattice. The large PL tuning reported here along with the insights into the mechanism of tuning and carrier dynamics are expected to boost the potential of Mn-doped CsPbCl3 NCs in light-powered devices.

Ambient Condition Mg2+ Doping Producing Highly Luminescent Green- and Violet-Emitting Perovskite Nanocrystals with Reduced Toxicity and Enhanced Stability.

Abstract: The lack of long-term stability, the presence of toxic lead, and a low photoluminescence (PL) efficiency are the major obstacles to the commercialization of lead-halide perovskite-based optoelectronic and photovoltaic devices. Herein we report a facile ambient condition doping protocol that addresses all three issues of the CsPbX3 perovskite nanocrystals (NCs) to a substantial extent. We show that the room-temperature treatment of these NCs with MgX2 results in the partial (18-23%) replacement of toxic lead, enhances the PL quantum yield of green-emitting CsPbBr3 (to ∼100% from ∼51%) and violet-emitting CsPbCl3 NCs (to ∼79% from ∼1%), and improves the stability under ambient conditions and in the presence of light and a polar solvent. Ultrafast pump-probe and temperature-dependent PL studies reveal that curing of the intrinsic structural disorder, introduction of some shallow energy levels close to the conduction band edge, and effective passivation of the halide deficiency contribute to the improved properties of the doped systems.

State of the Art and Prospects for Halide Perovskite Nanocrystals.

Abstract: Metal-halide perovskites have rapidly emerged as one of the most promising materials of the 21st century, with many exciting properties and great potential for a broad range of applications, from photovoltaics to optoelectronics and photocatalysis. The ease with which metal-halide perovskites can be synthesized in the form of brightly luminescent colloidal nanocrystals, as well as their tunable and intriguing optical and electronic properties, has attracted researchers from different disciplines of science and technology. In the last few years, there has been a significant progress in the shape-controlled synthesis of perovskite nanocrystals and understanding of their properties and applications. In this comprehensive review, researchers having expertise in different fields (chemistry, physics, and device engineering) of metal-halide perovskite nanocrystals have joined together to provide a state of the art overview and future prospects of metal-halide perovskite nanocrystal research.

Interstitial Mn2+-Driven High-Aspect-Ratio Grain Growth for Low-Trap-Density Microcrystalline Films for Record Efficiency CsPbI2Br Solar Cells

Abstract: It is imperative to develop a large-aspect-ratio grain-based thin film with low trap density for high-performance inorganic perovskite CsPbI2Br solar cells. Herein, by using Mn2+ ion doping to modulate film growth, we achieved CsPbI2Br grains with aspect ratios as high as 8. It is found that Mn2+ ions insert into the interstices of the CsPbI2Br lattice during the growth process, leading to suppressed nucleation and a decreased growth rate. The combination aids in the achievement of larger CsPbI2Br crystalline grains for increased JSC values as high as 14.37 mA/cm2 and FFs as large as 80.0%. Moreover, excess Mn2+ ions passivate the grain boundary and surface defects, resulting in effectively decreased recombination loss with improved hole extraction efficiency, which enhances the built-in electric field and hence increases VOC to 1.172 V. As a result, the champion device achieves stabilized efficiency as high as 13.47%, improved by 13% compared with only 11.88% for the reference device.

Colloidal Synthesis of Double Perovskite Cs2AgInCl6 and Mn-Doped Cs2AgInCl6 Nanocrystals.

Abstract: We show here the first colloidal synthesis of double perovskite Cs2AgInCl6 nanocrystals (NCs) with a control over their size distribution. In our approach, metal carboxylate precursors and ligands (oleylamine and oleic acid) are dissolved in diphenyl ether and reacted at 105 °C with benzoyl chloride. The resulting Cs2AgInCl6 NCs exhibit the expected double perovskite crystal structure, are stable under air, and show a broad spectrum white photoluminescence (PL) with quantum yield of ∼1.6 ± 1%. The optical properties of these NCs were improved by synthesizing Mn-doped Cs2AgInCl6 NCs through the simple addition of Mn-acetate to the reaction mixture. The NC products were characterized by the same double perovskite crystal structure, and Mn doping levels up to 1.5%, as confirmed by elemental analyses. The effective incorporation of Mn ions inside Cs2AgInCl6 NCs was also proved by means of electron spin resonance spectroscopy. A bright orange emission characterized our Mn-doped Cs2AgInCl6 NCs with a PL quantum...

Micro-light-emitting diodes with quantum dots in display technology

Abstract: Micro-light-emitting diodes (μ-LEDs) are regarded as the cornerstone of next-generation display technology to meet the personalised demands of advanced applications, such as mobile phones, wearable watches, virtual/augmented reality, micro-projectors and ultrahigh-definition TVs. However, as the LED chip size shrinks to below 20 μm, conventional phosphor colour conversion cannot present sufficient luminance and yield to support high-resolution displays due to the low absorption cross-section. The emergence of quantum dot (QD) materials is expected to fill this gap due to their remarkable photoluminescence, narrow bandwidth emission, colour tuneability, high quantum yield and nanoscale size, providing a powerful full-colour solution for μ-LED displays. Here, we comprehensively review the latest progress concerning the implementation of μ-LEDs and QDs in display technology, including μ-LED design and fabrication, large-scale μ-LED transfer and QD full-colour strategy. Outlooks on QD stability, patterning and deposition and challenges of μ-LED displays are also provided. Finally, we discuss the advanced applications of QD-based μ-LED displays, showing the bright future of this technology. Micrometre-sized light-emitting diodes (LEDs) based on quantum dots (QDs) will propel the next generation of display technologies, a review by leading researchers shows. Conventional LED designs, with phosphor coatings that convert light to different colours, are difficult to make smaller than 20 micrometres. Jr-Hau He at City University of Hong Kong and co-workers explain how this problem can be tackled using QDs, tiny particles whose optical properties can be tuned by varying their size, providing brighter and more precise colours. Ultra-high-resolution displays based on phospholuminescent QD-LEDs are now being released to the market thanks to finely-controlled methods for synthesising QDs and depositing them onto films. Further research should focus on the best ways to stabilise and protect QD films within LEDs, and to continue developing electroluminescent QD-LEDs, which could potentially outperform their phospholuminescent cousins.

Lead‐Free Halide Rb2CuBr3 as Sensitive X‐Ray Scintillator

Abstract: Scintillators are widely utilized for radiation detections in many fields, such as nondestructive inspection, medical imaging, and space exploration. Lead halide perovskite scintillators have recently received extensive research attention owing to their tunable emission wavelength, low detection limit, and ease of fabrication. However, the low light yields toward X-ray irradiation and the lead toxicity of these perovskites severely restricts their practical application. A novel lead-free halide is presented, namely Rb2 CuBr3 , as a scintillator with exceptionally high light yield. Rb2 CuBr3 exhibits a 1D crystal structure and enjoys strong carrier confinement and near-unity photoluminescence quantum yield (98.6%) in violet emission. The high photoluminescence quantum yield combined with negligible self-absorption from self-trapped exciton emission and strong X-ray absorption capability enables a record high light yield of ≈91056 photons per MeV among perovskite and relative scintillators. Overall, Rb2 CuBr3 provides nontoxicity, high radioluminescence intensity, and good stability, thus laying good foundations for potential application in low-dose radiography.