Stability Of Perovskite Quantum Dots Research Articles

Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots

All-inorganic CsPbI3 perovskite quantum dots (PQDs) hold significant potential for next-generation photovoltaics due to their unique optoelectronic properties, and the surface-bound ligand playing a key role in the stability and functionality of CsPbI3 PQDs. Initially used long-chain ligands in PQDs synthesis stabilize the black phase but hinder charge transport when employed to solar cells, necessitating their replacement with shorter ones. However, this leads to the formation of surface defects and loss of tensile strain, resulting in the transition to the undesired orthorhombic phase (δ-phase) and compromising PQD solar cell performance. Therefore, developing a ligand exchange process that achieves the optimal balance between conductivity and stability in PQD solid films continues to be a significant challenge. To address these issues, we developed an efficient ligand-exchange process utilizing a multifaceted anchoring ligand, 2-thiophenemethylammonium iodide (ThMAI). The larger ionic size of ThMA+ compared to Cs+ facilitates the restoration of surface tensile strain in PQDs, while its thiophene and ammonium groups enable effective passivation of surface defects. Owing to these advantages, ThMAI-treated CsPbI3 PQD thin films exhibit improved carrier lifetime, uniform PQD orientation, and increased ambient stability. As a result, the ThMAI-treated CsPbI3 PQD solar cells demonstrate an improved power conversion efficiency (PCE) of 15.3 % and an enhanced device stability.

High‐Leakage‐Resistance and Low‐Turn‐On‐Voltage Upconversion Devices Based on Perovskite Quantum Dots

AbstractIn recent years, the remarkable optoelectronic characteristics exhibited by perovskite quantum dots (PQDs) have captured significant attention, which has spurred numerous investigations and novel applications. Nonetheless, the development of solution‐processed upconversion devices (UCDs) has predominantly centered around the utilization of organic materials, 3D perovskite films, and II‐VI quantum dots. In this work, PQDs are utilized for the first time as emission materials to enhance UCD performance. The stability of PQDs, synergistic coverage effect between PQDs and hole‐transporting layers (HTLs), and the interfaces of CGL/HTL are investigated in an attempt to identify the primary factor affecting UCD performance. The optimized UCD incorporating with effective TAPC HTLs demonstrate a maximum luminance of 463.9 cd m−2 at 520 nm (biased at 12 V and irradiated under 785 nm NIR light) accompanied by significant current gains of 167 times (at 3.4 V) and a noteworthy photon‐to‐photon conversion efficiency of 5.68% (at 12 V). The impressive performance is accompanied by a remarkably low turn‐on voltage of 1.4 V and a high leakage voltage of up to 12 V, making the highest record reported for solution‐processed UCDs.

Green synthesis of highly luminescent CsPbBr3 quantum dots through silica coating and post-treatment with ligands

All-inorganic perovskite quantum dots (PQDs) have received considerable attentions due to their fascinating optical properties. However, the mainstream preparation methods rely on toxic solvents, raising significant environmental and safety concerns. In this work, ethyl acetate was chosen as the environmentally friendly anti-solvent to prepare silica-coated CsPbBr3 PQDs using a aminoalkoxysilane-assisted reprecipitation–encapsulation method. The as-prepared PQDs exhibited tunable emission wavelength and a medium photoluminescence quantum yield (PLQY) of 60%. Furthermore, CsPbBr3 PQDs were post-treated by different ligands with the aim of passivating surface defects. This strategy successfully mitigated the presence of surface defects and minimized non-radiative recombination losses in PQDs. As a result, the PLQY (achieving up to 73%) and stability of PQDs were substantially enhanced (luminescence stability improved by about 40% under the same test conditions). Our studies offer a novel approach for the environmentally friendly large-scale production of PQDs, opening up new possibilities for their practical applications.

An innovative strategy: ultra-stable alkaline earth modified CsPbBr3 quantum dots glass was prepared by washing-heat cycle for high definition backlight display

All-inorganic perovskite quantum dots (QDs) as high-quality materials for backlight display are still limited by their own low stability. Herein, the crystallization of CsPbBr3 (CPB) QDs in a glass matrix was promoted by modifying the glass network structure with alkaline earth metals (Mg, Ca, Sr, Ba). What's more, a washing-heat treatment cycle strategy was used to optimize the best-modified sample (CPB–Mg). Among them, CPB-12Mg (add 12% MgO) showed a high photoluminescence quantum yield (PLQY = 62%) after the cycling process. More surprisingly, the six-step washing-heat treated-sample (CPB–12Mg-6) showed excellent stability. When CPB-12Mg-6 was irradiated for 240 h at 60°C, 90% relative humidity (RH), and 880 W/m2 blue light power (60°C, 90% RH, 880 W/m2), the original 90% fluorescence emission could still be maintained. Subsequently, a series of CPB-12Mg-6/CsPbBr1.5I1.5@PS light conversion films were prepared by the master batch blending method. The backlight conversion film for liquid crystal display (LCD) achieves a wide color gamut that covers 126% of the NTSC 1953 and 93.6% of the Rec.2020 standard. This innovative washing-heat treatment cycle strategy provides a new idea for improving the stability of perovskite quantum dots.

In-situ synthesis of MAPbBr3 perovskite quantum dot-polycaprolactone composites with enhanced photoluminescence quantum yield and stability

Polymer encapsulation is regarded as an efficient strategy to enhance the stability of perovskite quantum dots (PQDs), and also endows the perovskites with advantages in mechanical properties and processibility. In this work, polymer encapsulation was achieved by in-situ synthesis of PQDs in polycaprolactone (PCL) polymer, which avoiding time-consuming process of blending polymer with PQDs. Moreover, besides of acting as encapsulation matrix, PCL in toluene could provide large nucleation sites for PQDs formation, resulting in the relatively smaller PQDs size and enhanced photoluminescence quantum yield (PLQY) with respect to the composites prepared by physical blending. Profiting from PCL encapsulation, the as-synthesized PQDs-PCL composites exhibited enhanced stability against UV light, water and heat. The strong interaction between PQDs and PCL in composites with high PCL concentration could endow them with more significantly improved PL stability under UV-light illumination and relatively better mechanical properties compared to the composites with high PQDs concentration. This work provides an efficient method to synthesize PQDs-polymer composites with enhanced PLQY and stability, which would promote practical applications of PQDs materials in the optoelectronic applications.

Improving anion-exchange efficiency and spectrum stability of perovskite quantum dots via an Al3+ bonding-doping synergistic effect.

Anion-exchange reactions are recognized as a vital and facile post-synthesis method to precisely manipulate the emission spectra of perovskite quantum dots (QDs). However, the anion-exchange process often induces adverse structural evolution and trap-mediated mechanisms, so mixed-halide perovskite QDs suffer inefficient anion exchange and poor spectra-stability issues, which limits access to high-quality primary color perovskite QDs for display applications. Here we report an Al3+ bonding-doping synergistic strategy for manufacturing stable mixed Br/Cl deep-blue perovskite QDs. By doping Al3+ into perovskite QDs, highly-efficient Cl- anion exchange and a large-range blue shift of the PL spectrum (∼62 nm with only 0.1 mmol of Cl feed) can be easily achieved. Notably, the Al3+-mediated deep-blue emission sample exhibits superior stability against moisture and electric fields. It also shows an elevated valence band maximum level. Based on the anion-exchanged QDs, a spectrum-stable deep-blue QLED with an EQE of 1.38% at 463 nm is achieved. Our findings demonstrate a feasible and promising strategy for developing high-performance deep-blue perovskite materials and optoelectronic devices.

Stability strategies of perovskite quantum dots and their extended applications in extreme environment: A review

• The developments of synthetic methods of perovskite quantum dots were highlighted. • The decomposition mechanisms of perovskite quantum dots were deeply analyzed. • The various methods to enhance the stability of perovskite quantum dots are introduced. • They have application potential in photoelectric devices, sensor, catalytic, bioimaging. Perovskite quantum dots (PQDs) have become one of the hot research topics in materials science due to their excellent optical and electrical properties. However, they are not widely used in various fields because of their insufficient structural stability. In this review, we discuss the structural characteristics, preparation methods, surface modifications and other aspects of PQDs to overcome their stabilities in extreme environment. We also summarize the decomposition mechanism of its own structure caused by the influence of external environment. Also, a few ways to enhance the stability of PQDs are introduced. This review is devoted to systematically analyzing the influence of different interface structure designs and the design growth in the confined space of PQDs on the optical performance and stability of perovskite quantum dots. Finally, the development and application of PQDs in expanding fields are summarized, which may point out the new directions.

Stable CsPbBr3 Achieved by Porphyrin–Thiol Surface Management and Their Dual‐Stimuli Responsive for Optical Encoding

AbstractSurface ligand management plays an essential role in improving the stability of perovskite quantum dots (QDs) and endowing them with novel property. Herein, a red fluorescence porphyrin‐thiol (named Por‐SH) is applied to adjust the surface and stimuli responsiveness of CsPbBr3 QDs. According to the theoretical and experimental results, Por‐SH can bind tightly to the exposed Pb of CsPbBr3 QDs, thus leading to the formation of Por‐SH‐QDs with an excellent resistance to water and UV light. Moreover, CsPbBr3 act as energy donors to improve the photoresponse of Por‐SH through energy transfer, especially when heated. Notably, the Por‐SH and QDs behave differently in terms of response to the temperature in the Por‐SH‐QDs system. Therefore, the Por‐SH‐QDs are capable of reversible stimuli–response property in the presence of heat/cool stimuli when excited by UV light. Finally, the disposable or reversible optical encoding label based on Por‐SH‐QDs and QDs is obtained by combining stability and the responsiveness to stimuli. Through the selection of suitable ligands, the surface of QDs is efficiently managed, which can not only mitigate instability but also endow perovskite QDs with the responsiveness to stimuli.

Ligand exchange engineering of FAPbI3 perovskite quantum dots for solar cells

Formamidinium lead triiodide (FAPbI3) perovskite quantum dots (PQDs) show great advantages in photovoltaic applications due to their ideal bandgap energy, high stability and solution processability. The anti-solvent used for the post-treatment of FAPbI3 PQD solid films significantly affects the surface chemistry of the PQDs, and thus the vacancies caused by surface ligand removal inhibit the optoelectronic properties and stability of PQDs. Here, we study the effects of different anti-solvents with different polarities on FAPbI3 PQDs and select a series of organic molecules for surface passivation of PQDs. The results show that methyl acetate could effectively remove surface ligands from the PQD surface without destroying its crystal structure during the post-treatment. The benzamidine hydrochloride (PhFACl) applied as short ligands of PQDs during the post-treatment could fill the A-site and X-site vacancies of PQDs and thus improve the electronic coupling of PQDs. Finally, the PhFACl-based PQD solar cell (PQDSC) achieves a power conversion efficiency of 6.4%, compared to that of 4.63% for the conventional PQDSC. This work provides a reference for insights into the surface passivation of PQDs and the improvement in device performance of PQDSCs.Graphical abstract

Core-shell structuredCsPbBr3/Sn-TiO2 nanocrystals for visible-light-driven photocatalyst in aqueous solution

All-inorganic perovskite materials have attracted much attention in the field of photocatalysts due to their unique photoelectric properties.However, the inherent poor stability of perovskite quantum dots significantlyhinders their practical applications. Herein, to settle the instabilities of inorganic perovskite materials, Sn-TiO2 coated CsPbBr3 quantum dots named CsPbBr3/Sn-TiO2, are fabricated via resaturated recrystallization, sol–gel coating and solvothermal crystallization.The XRD results demonstrated that the core–shell structure of CsPbBr3/Sn-TiO2 nanocrystals was successfully synthesized.Moreover, excellent dispersion is verified for CsPbBr3/Sn-TiO2 nanocrystals with a core–shell structure by TEM. The particle size of CsPbBr3/Sn-TiO2 nanocrystals is 15–30 nm, where the core size for CsPbBr3 quantum dots is 4–8 nm, and the Sn-TiO2 shell thickness is 2–8 nm.The photocatalytic activity of nanocomposites was studied by the photodegradation of RhB aqueous solution under the irradiation of 100 mWcm−2 air mass 1.5 global AM1.5G sunlight. Compared with traditional photocatalyst P25, the core–shell structured CsPbBr3/Sn-TiO2 nanocrystals exhibited better photocatalytic performance, with a degradation efficiency of 96.6% and a degradation rate constant of 10.68 × 10-2 min−1 in 30 min of catalytic time, which was five times higher than that of P25.The core–shell structured CsPbBr3/Sn-TiO2 nanocrystals have long-term stability in water system and have potential practical application value in the field of environmental governance.

Multiple-Route Exciton Recombination Dynamics and Improved Stability of Perovskite Quantum Dots by Plasmonic Photonic Crystal.

We have studied the excited-state exciton recombination dynamics of perovskite quantum dots (QDs) through time-resolved photoluminescence (PL), PL blinking, PL intensity-dependent lifetime modulation, and long-term photostability tests. The various spectroscopic characterizations elucidate that the perovskite QDs have multiple intrinsic exciton recombination routes even in a single QD, i.e., exciton, biexciton, and positive/negative trions, which are dissimilarly contributed to ON and OFF state emissions. We also find that the enhanced radiative recombination from placing green QDs on a photonic Ag nanotip array induces notably improved long-term PL stability. We consider that the accelerated radiative recombination of QDs by strong coupling with the plasmonics of the photonic Ag nanotip array, while eliminating nonradiative pathways, is proven to be a critical factor for improved long-term stability.

Enhanced Air Stability of Perovskite Quantum Dots by Manganese Passivation

Organic-inorganic perovskite quantum dots (PeQDs) have attracted attention due to their excellent optical properties, e.g., high photoluminescence quantum yields (PLQYs; >70%), a narrow full width at half maximum (FWHM; 25 nm or less), and color tunability adjusted by the halide components in an entire tunability (from 450 nm to 730 nm). On the other hand, PeQD stability against air, humidity, and thermal conditions has still not been enough, which disturbs their application. To overcome these issues, with just a focus on the air stability, Mn2+ ion passivated perovskite quantum dots (Mn/MAPbBr3 QDs) were prepared. Mn2+ could be expected to contract the passivating layer against the air condition because the Mn2+ ion was changed to the oxidized Mn on PeQDs under the air conditions. In this research, Mn/MAPbBr3 QDs were successfully prepared by ligand-assisted reprecipitation (LARP) methods. Surprisingly, Mn/MAPbBr3 QD films showed more than double PLQY stability over 4 months compared with pure MAPbBr3 ones against the air, which suggested that oxidized Mn worked as a passivating layer. Improving the PeQD stability is significantly critical for their application.

Modified α-Al2O3 wafer: Enhance the stability of perovskite quantum dots with wide colour gamut for white light-emitting diodes

Recently, perovskite has received extensive attention due to their excellent photoelectric properties, while the instability of perovskite quantum dots (PQDs) has always troubled us. Herein, we proposed a simple coating mechanism to protect PQDs. Using oleic acid (OA) for etching α-Al2O3 wafer to make the surface appear pore structure, and the PQDs was coated within the modified α-Al2O3 wafer, thereby improving the stability of PQDs. The CsPbX3@α-Al2O3 composite material can achieve the emission of blue-green–red (436 nm to 636 nm) through adjustable luminescence wavelength. The photoluminescence (PL) intensity of CsPbBr3@α-Al2O3 composite material exposure to the air after 28 days can maintain over 50%. It is worth noticing that the photoluminescent quantum yield (PLQY) of CsPbBrI2@α-Al2O3 composite material can reach 58%, the colour purity of CsPbBr3@α-Al2O3 and CsPbBrI2@α-Al2O3 achieve 97.1% and 99.8%, respectively. It was due to the high colour purity of the composite materials can the selected CIE colour coordinate monochromatic light encompassed 114% of NTSC colour gamut. Moreover, the warm white light-emitting diode (WLED) yielded bright natural white light and showed the luminous efficiency (LE) of 86.58 lm/W, colour rendering index (CRI) of 86.9, correlated colour temperature (CCT) of 4602 K. The LE and CRI reaches a relatively balanced value, which showed that this composite material has a certain development prospect in the WLED field.

Low-temperature synthesis of zirconium silicate stabilized perovskite quantum dot composite material

Perovskite quantum dots (PQDs) have been devised as an efficient narrow half-width phosphor and received extensive attention due to their high photoluminescence quantum yield (PLQY), adjustable emission colour and high colour purity. However, the low stability of perovskite quantum dots seriously affects its performance and application. Here, we have proposed a simple ligand-assisted precipitation method to encapsulate PQDs in zirconium silicate (ZrSi). Owing to the special stacked structure and high specific surface area of ZrSi, the composite material exhibits extremely high humidity stability and thermal stability compared to pure PQDs. Both ZrSi/CH3NH3PbBr3 PQDs and ZrSi/CsPbBr3 PQDs prepared by ZrSi packaging exhibit excellent luminescence properties, and the three-colour phosphor composite prepared by changing the halogen ratio has a very high colour gamut. In addition, ZrSi/CH3NH3PbBr3 PQDs and ZrSi/CsPbBr3 PQDs assembled white light-emitting diodes (LEDs) also have very excellent optical properties. This work provides a new method for the synthesis of high-stability perovskite quantum dots for white LED and display materials by using stacked structure materials.

Enhanced Optical Properties and Stability of CsPbBr3 Nanocrystals Through Nickel Doping

AbstractTo improve the quantum efficiency and stability of perovskite quantum dots, the structural and optical properties are optimized by varying the concentration of Ni doping in CsPbBr3 perovskite nanocrystals (PNCs). As Ni doping is gradually added, a blue shift is observed at the photoluminescence (PL) spectra. Ni‐doped PNCs exhibit stronger light emission, higher quantum efficiency, and longer lifetimes than undoped PNCs. The doped divalent element acts as a defect in the perovskite structure, reducing the recombination rate of electrons and holes. A stability test is used to assess the susceptibility of the perovskite to light and moisture. For ultra‐violet light irradiation, the PL intensity of undoped PNCs decreases by 70%, whereas that of Ni‐doped PNCs decreases by 18%. In the water addition experiment, the PL intensity of Ni‐doped PNCs is three times that of undoped PNCs. For CsPbBr3 and Ni:CsPbBr3 PNCs, a light emitting diode is fabricated by spin‐coating. The efficiency of Ni:CsPbBr3 exceeds that of CsPbBr3 PNCs, and the results significantly differ based on the ratio. A maximum luminance of 833 cd m–2 is obtained at optimum efficiency (0.3 cd A–1). Therefore, Ni‐doped PNCs are expected to contribute to future performance improvements in display devices.

Engineering CsPbBr3 quantum dots with efficient luminescence and stability by damage-free encapsulation with a-SiCx:H

Although encapsulation is an effective technique to improve the stability of perovskite quantum dots (PQDs), they are prone to photoluminescence (PL) degradation during encapsulation. Herein, a damage-free plasma-based encapsulation technique in combination with real-time in situ diagnosis is designed for CsPbBr3 QDs films. The CH4/SiH4 plasma has little destructive effects on the CsPbBr3 QDs. The a-SiCx:H films prepared with the CH4/SiH4 plasma by low-temperature plasma-enhanced chemical vapor deposition protect the CsPbBr3 QDs from surface damage during encapsulation, so that the intrinsic PL efficiency is maintained. Furthermore, the PL intensity is improved by increasing the carbon concentration in a-SiCx:H and the CsPbBr3 QDs films encapsulated by a-SiCx:H show long term stability under harsh conditions such as prolonged air exposure, UV light illumination for more than 60 days, immersion in water, as well as thermal treatment at 205 oC.

Highly Stable Perovskite Quantum Dots Modified by Europium Complex for Dual-Responsive Optical Encoding.

Inorganic perovskite quantum dots (QDs) have attracted great scientific attention in the field of luminescent materials, but the application has been limited by the inferior stability that results from highly dynamic capping ligands. In this work, we use a rare-earth complex to modify perovskite QDs with ligand exchange to realize perovskite functionalization; meanwhile, the stability of perovskite QDs is greatly improved. Density functional theory calculation results show that the adsorption energy of the europium complex to QDs is higher than that with traditional ligands, which provides a thermodynamic basis for stability improvement. Furthermore, the modified QDs exhibit attractive dual-response property, including temperature and pH response ascribed to QDs and europium complexes, respectively. The superior property can be applied to multi-stimuli-responsive optical encoding, which is further capable of enhancing the security of encrypted information. This study not only affords a strategy for the synthesis of highly stable perovskites but also provides a method for the functionalization of perovskites.

54.1: Invited Paper: Perovskite Light Emitting Diode

Metal halide perovskite materials occupy an increasingly important position in the field of optoelectronic materials due to their excellent light absorption properties, long carrier dispersion length and high mobility. However, the instability of perovskite materials is still a major factor constraining its development. So, its' important to improve the stability of perovskite materials in air and even to produce high‐performance LEDs in air. Here, we proposed a simple way to improve the stability of perovskite quantum dots and achieved the preparation of perovskite light‐emitting diodes in air. And green PQDs‐LED devices are fabricated by inkjet printing.

Dual-encapsulation for highly stable all-inorganic perovskite quantum dots for long-term storage and reuse in white light-emitting diodes

Although perovskite quantum dots (PQDs) have fascinating optical performances and wide uses in light-emitting diodes (LEDs), laser and photodetectors etc., their commercialization and practical applications are seriously hampered by the poor stability against moisture or water, heat, photo-oxidation and ion exchange. Herein, we report a dually encapsulating strategy of PQDs in fluorinated silica (FSiO2) and porous polydimethylsiloxane (PPDMS) foam. Owning to the superhydrophobic and thermal insulation layers, the dually-encapsulated CsPbBr3 QDs are very stable in the moisture, heat, and irradiation environment and can be long-term stored in air environment for at least 3 months without losing their optical properties. Moreover, the FSiO2-coated CsPbBr3 QDs can be easily released out from PPDMS foam and applied in white LEDs to display pure white emission with ideal CIE (Commission Internationale de L’Eclairage 1931) chromaticity coordinate of (0.33, 0.33). This novel dual-encapsulation strategy through combination of solid airtight shells and thermally insulated porous materials provides a new idea and solution to improve the stability of perovskite quantum dots.

A Cyan Emitting CsPbBr3 Perovskite Quantum Dot Glass with Bi Doping

CsPbBr3:xBi3+ quantum dot glass was prepared by using traditional melting-quenching and heat treatment processes. The effects of Bi doing on the sinter of the precursor of glass and the crystalline of the perovskite quantum dot were discussed detailly. By doping Bi2O3 into the borosilicate glass matrix, the melting temperature was reduced to 900 °C. The tunable emission of CsPbBr3 quantum dots from 523 to 493 nm was achieved with suitable Bi2O3 doping. Due to the protection of the inorganic glass matrix, the prepared CsPbBr3 quantum dots still exhibit excellent thermal stability after multiple thermal cycles and thermal shocks. This provides a good solution to the problem of poor thermal stability of perovskite quantum dots.