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The utilization of perovskite quantum dots (PQDs) in photoelectric devices is indeed an area of intense research due to their advantageous properties such as tunability of visible light and efficient light emission. In this study, mixed CsPbI 3 and FAPbI 3 PQD dispersions were successfully employed for cation exchange to prepare red-color Cs 1−x FA x PbI 3 PQD with the photoluminescence (PL) wavelength from 689 nm (x = 0) to 778 nm (x = 1). It is also found that the aggregation of Cs 1−x FA x PbI 3 PQD films were strongly dependent on x. When x from 0 to 0.6, the holes in PQD thin films were gradually improved. On the opposite, when x > 0.6, the PQDs thin films returned more and more holes due to an excess of FA + cations. The resulting Cs 1-x FA x PbI 3 PQD based light-emitting diodes (LEDs) also demonstrated tunable emission wavelengths, and it is worth mentioning that the maximum external quantum efficiency (EQE) of 11.22 % was achieved with an emission wavelength of 758 nm when x = 0.6. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM AUTHOR]

Perovskite quantum dots (QDs) have showed excellent optoelectronic properties to extend the application range of novel solid-state lighting, such as perovskite QD based LEDs (QD-LEDs). However, the traditional device structure of perovskite QD-LEDs employed PEDOT:PSS as a hole inject layer (HIL), which impairs stability due to acidic surface characteristics. This study proposes the sputtered NiO films as an HIL to replace acidic PEDOT:PSS. The NiO films with significantly different characteristics were prepared by controlling the sputtering parameters to investigate the devices' performance of NiO-based CsPbBr3 QD-LEDs. The optimized device showed an excellent performance with maxima luminescence of 20,118 cd/m2 and an external quantum efficiency (EQE) up to 3.63%. [ABSTRACT FROM AUTHOR]

In this study, blue perovskite quantum dots (PQDs) were prepared using didodecyldimethylammonium bromide (DDAB), which can passivate surface defects caused by the loss of surface ligands and reduce particle size distribution. After the passivation of DDAB, blue CsPbClxBr3−x PQDs dispersed in n-octane produced a more compact and uniform PQD thin film than the non-passivated ones. The resulting device showed a stabile lifetime, and an EL peak of 470 nm and a maximum EQE of 1.63% were obtained at an operating voltage of 2.6 V and a current density of 0.34 mA/cm2. This work aims to provide a simple method to prepare blue-emitting PQDs and high-performance PQD-based light-emitting devices. [ABSTRACT FROM AUTHOR]

Stretchable microcavity lasers reveal potential application in flexible displays, biomedicine, and wearable devices in the near future. In this work, we investigated the characteristic of amplified spontaneous emission (ASE) from all inorganic CsPbBr3 QDs on a flexible PET substrate with the assistance of biocompatible silk fibroin (SF) film. In comparison with the sample on PET directly, the ASE of all-inorganic perovskite film revealed a lower threshold of 32.7 μJ/cm2, higher slope efficiency, and a larger gain coefficient of around 100.0 cm−1 owing to the better stack and good arrangement of the CsPbBr3 QDs on top of the SF film. For the temperature-dependent ASE measurement, the larger characteristic temperature of around 277 K is obtained from CsPbBr3 QD/SF film, and the emission peak reveals a slight shift with temperature variation, which indicates its temperature-insensitive property. As the curvature of flexible substrate increases under the mechanical bending, the lasing threshold of CsPbBr3 QD/SF film was reduced along with the increase in slope efficiency owing to the enhancement in the index guiding effect. [ABSTRACT FROM AUTHOR]

In this study, we developed a photodetector and humidity sensor based on zinc oxide nanowires (ZnO NWs) with CsPbBr3 perovskite quantum dots (PQDs). PQDs are ideally suited to semiconductor sensors due to their excellent optoelectronic properties, including the high carrier mobility, high absorption coefficient, and effective charge transfer at heterojunctions. The ZnO NWs were created via chemical bath deposition, and PQDs were created via a one-step injection method. I–V curves revealed that the current leakage of PQD/ZnO NWs was lower than that of ZnO NWs. PQD/ZnO NWs also generated a larger number of photogenerated carriers, which improved sensor responses, regardless of the illumination wavelength. Under UV illumination, the photocurrent of both structures decreased with an increase in relative humidity; however, under green light illumination, the photocurrent of PQD/ZnO NWs increased with humidity. This study also investigated the optical properties of the two structures as candidate sensor mechanisms. [ABSTRACT FROM AUTHOR]

This work presents an ultrasonic synthesis method for perovskite quantum dots (QDs). The structure, particle size and morphology of perovskite quantum dots were analyzed, and the differences between the dispersion of the organic perovskite quantum dots prepared with and without the ultrasonic treatment were discussed. The results showed that the ultrasonic synthesis contributed to smaller particle sizes and a more uniform particle-size distribution. Tunable emission peaks and adsorption edges of CH 3 NH 3 PbX 3 (X = Cl, Br and I) QDs prepared with different chemical compositions were also generated using the ultrasonic synthesis method, and hence, an extremely wide color gamut was obtained. [ABSTRACT FROM AUTHOR]

Inverted-type perovskite solar cells offer the potential of fabrication by low-temperature solution processing as an alternative to conventional-type perovskite solar cells. PEDOT:PSS is commonly used as the hole transport layer (HTL), but its acidic nature may damage the reliability and stability of the photovoltaic device. In this study, we demonstrate the use of MoO x and WO x HTLs as an alternative to PEDOT:PSS for planar CH 3 NH 3 PbI 3 perovskite solar cells. Furthermore, the MoO x and WO x HTLs are treated using a UV-ozone treatment to improve the surface coverage of the perovskite layer. The resultant conversion efficiency (PCE) for the best cells at AM1.5G illumination with a shadow mask was 13.1%. [ABSTRACT FROM AUTHOR]

This paper reports on the fabrication of ZnO nanowalls for use as an electron collecting layer (ECL) in CH 3 NH 3 PbI 3 perovskite solar cells (PSCs). Two-dimension ZnO nanowalls were grown using a low-temperature chemical bath method with a thin Al film as a seed layer. We compared electron collecting layers based on nanowalls and sol–gel derived ZnO thin film in PSCs and sought to identify the mechanism underlying the collection of electrons. The proposed ZnO nanowalls achieved a fill factor significantly higher than that of ZnO thin films, which translated into a remarkable improvement in power conversion efficiency, reaching 13.6% under AM 1.5G illumination. [ABSTRACT FROM AUTHOR]

• A ligand-exchange reaction using TOAB was present for stable CsPbI 3−x Br x quantum dots. • TOAB-passivated QDs showed environmental resistance, such as, moisture, light, and heat. • TOAB-passivated devices exhibited a maximum luminescence of 1345 cd/m2 and a maximum external quantum efficiency of 11.7%. In this study, we demonstrate a ligand-exchange reaction using tetraoctylammonium bromide (TOAB) salts for the as-synthesized CsPbI 3 perovskite nanoparticles (NPs) to ensure NPs with stable and improved device performance. TOAB passivation provides a negatively polarized halide-rich surface, higher steric hindrance, and a small amount of Br− anions in the NP lattice to significantly improve the NP stability. The red NP-based light-emitting diodes (NpLEDs) based on TOAB-passivated NPs also exhibited excellent performance because of shorter ligands and stable NPs, with a maximum luminescence of 1345 cd/m2 and a maximum external quantum efficiency of 11.7%. [ABSTRACT FROM AUTHOR]

Hybrid organic−inorganic and all-inorganic metal halide perovskite nanoparticles (PNPs) have shown their excellent characteristics for optoelectronic applications. We report an atmospheric process to embed formamidinium CH(NH2)2PbI3 (FAPbI3) PNPs in silica protective layer at room temperature (approximately 26 °C) employing (3-aminopropyl) triethoxysilane (APTES). The resulting perovskite nanocomposite (PNCs) achieved a high photoluminescence (PL) quantum yield of 58.0% and good stability under atmospheric moisture conditions. Moreover, the PNCs showed high PL intensity over 1 month of storage (approximately 26 °C) and more than 380 min of PNCs solutions in DI water. The studied near-infrared (NIR) light-emitting diode (LED) combined a NIR-emitting PNCs coating and a blue InGaN-based chip that exhibited a 788 nm electroluminescence spectrum of NIR-LEDs under 2.6 V. This may be a powerful tool to track of muscle and disabled patients in the detection of a blood vessel. [ABSTRACT FROM AUTHOR]

In this study, the performances of red CsPbI3-based all-inorganic perovskite quantum-dot light-emitting diodes (IPQLEDs) employing polymeric crystalline Poly(3-hexylthiophene-2,5-diyl) (P3HT), poly(9-vinycarbazole) (PVK), Poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine (Poly-TPD) and 9,9-Bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (VB-FNPD) as the hole transporting layers (HTLs) have been demonstrated. The purpose of this work is an attempt to promote the development of device structures and hole transporting materials for the CsPbI3-based IPQLEDs via a comparative study of different HTLs. A full-coverage quantum dot (QD) film without the aggregation can be obtained by coating it with VB-FNPD, and thus, the best external quantum efficiency (EQE) of 7.28% was achieved in the VB-FNPD device. We also reported a standing method to further improve the degree of VB-FNPD polymerization, resulting in the improved device performance, with the EQE of 8.64%. [ABSTRACT FROM AUTHOR]

In this paper, a thermally crosslinkable 9,9-Bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-fluorene-2,7-diamine (VB-FNPD) film served as the hole transporting layer (HTL) of perovskite CsPbBr3 quantum-dot light-emitting diodes (QD-LEDs) was investigated and reported. The VB-FNPD film crosslinked at various temperatures in the range of 100~230 °C followed by a spin-coating process to improve their chemical bonds in an attempt to resist the erosion from the organic solvent in the remaining fabrication process. It is shown that the device with VB-FNPD HTL crosslinking at 170 °C has the highest luminance of 7702 cd/m2, the maximum current density (J) of 41.98 mA/cm2, the maximum current efficiency (CE) of 5.45 Cd/A, and the maximum external quantum efficiency (EQE) of 1.64%. Our results confirm that the proposed thermally crosslinkable VB-FNPD is a candidate for the HTL of QD-LEDs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are one of the highly promising new‐generation photovoltaic technologies. One of the remaining challenges for commercializing PSCs is to prepare high‐quality, large‐area perovskite films in an ambient atmosphere reproducibly using less toxic materials. Herein, a nonvolatile, less toxic substance, 2‐pyrrolidinone (2P), is used as a complexant solvent for the perovskite precursor solution. Combining this with a newly developed spin‐assisted solvent extraction (SASE) crystallization method, a high‐quality perovskite film is prepared in air reproducibly. The nonvolatile nature of 2P and the formation of MAI–PbI2–2P adduct widen the time window for antisolvent engineering, and SASE enhances the solvent exchange rate of the precursor film to form a high‐quality perovskite film in air. An inverted cell (based on the postsolvent‐treated perovskite absorber) exhibits a power conversion efficiency of more than 18%. This film preparation method is feasible for depositing a high‐quality mixed‐cation or mixed‐cation, mixed‐halide perovskite film on both PEDOT:PSS and TiO2 surfaces to fabricate inverted and regular PSCs, respectively, to achieve efficiencies of more than 16%. More importantly, high‐quality, large‐area MAPbI3 film is prepared reproducibly in air for fabricating perovskite submodules to achieve an efficiency of 14% (verified at 13.04% after the cell is packed for efficiency evaluation). [ABSTRACT FROM AUTHOR]

High-quality perovskite CsPbBr3 quantum dots (QDs-CsPbBr3) were prepared using the ultrasonic oscillation method, which is simple and provides variable yield according to requirements. The emission spectra over a large portion of the visible spectral region (450–650 nm) of QD-CsPbX3 (X = Cl, Br, and I) have tunable compositions that can be halide exchanged using the halide anion exchange technique and quantum size-effects. A strong peak with high intensity of (200) lattice plane of purified QDs-CsPbBr3 film is obtained, confirming the formation of an orthorhombic perovskite crystal structure of the Pnma space group. The photoluminescence of QDs-CsPbBr3 was characterized using a narrow line-width emission of 20 nm, with high quantum yields of up to 99.2%, and radioactive lifetime increasing to 26 ns. Finally, through the excellent advantages of QDs-CsPbBr3 mentioned above, purified perovskite QDs-CsPbBr3 as an active layer was utilized in perovskite quantum dot light-emitting diodes structure applications. As a result, the perovskite QDs-CsPbBr3 light-emitting diodes (LEDs) exhibits a turn-on voltage of 7 V and a maximum luminance of 5.1 cd/m2. [ABSTRACT FROM AUTHOR]

Perovskite CsPbBr3 quantum dot (CsPbBr3-QD) recovery was performed using lead scrap from lead storage batteries. The perovskite CsPbBr3-QD characteristics were analyzed using different PbO/recycled PbO2 ratios. Scanning electron microscopy (SEM) was used to observe the film surface morphology and cross-section. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to observe the perovskite CsPbBr3-QDs' structural characteristics. A photoluminescence (PL) measurement system was used to analyze the optical properties. The results show that lead scrap from lead–acid batteries as a material for perovskite CsPbBr3-QD production can be successfully synthesized. This saves material and also proves that recycling is valuable. The proposed approach is helpful for future material shortages and materials not easily accessible. Although the efficiency is not very high, this process will be purified using recycled lead in the future to achieve higher quantum yield. [ABSTRACT FROM AUTHOR]

The poor stability of CsPbX3 quantum dots (QDs-CsPbX3) under wet conditions is still considered to be a key issue. In order to overcome this problem, this study presents a high molecular weight polymer matrix (polymethylmethacrylate, PMMA) incorporated into the QDs-CsPbBr3 to improve its stability and maintain its excellent optical properties. In this study, the Cs2CO3, PbO, Tetrabutylammonium Bromide (TOAB) powder, oleic acid, and toluene solvent were uniformly mixed and purified to prepare high-quality QDs powders. Then, hexane was used as a dispersing agent for the QD powder to complete the perovskite QDs-CsPbBr3 solution. Finally, a solution with different proportions of quantum dots CsPbBr3 and PMMA was prepared and discussed. In the preparation of thin films, firstly, a thin film with the structure of glass/QD-CsPbBr3/PMMA was fabricated in a glove box using a well-developed QDs-CsPbBr3 solution by changing the ratio of CsPbBr3:PMMA. The material analysis of QDs-CsPbBr3 thin films was performed with photoluminescence (PL), transmittance, absorbance, and transmission electron microscopy (TEM). The structures and morphologies were further examined to study the effect of doped PMMA on perovskite QDs-CsPbBr3. [ABSTRACT FROM AUTHOR]

We describe a method to enhance power conversion efficiency (PCE) of MAPbI3 perovskite solar cell by inserting a FAPbX3 perovskite quantum dots (QD-FAPbX3) layer. The MAPbI3 and QD-FAPbX3 layers were prepared using a simple, rapid spin-coating method in a nitrogen-filled glove box. The solar cell structure consists of ITO/PEDOT:PSS/MAPbI3/QD-FAPbX3/C60/Ag, where PEDOT:PSS, MAPbI3, QD-FAPbX3, and C60 were used as the hole transport layer, light-absorbing layer, absorption enhance layer, and electron transport layer, respectively. The MAPbI3/QD-FAPbX3 solar cells exhibit a PCE of 7.59%, an open circuit voltage (Voc) of 0.9 V, a short-circuit current density (Jsc) of 17.4 mA/cm2, and a fill factor (FF) of 48.6%, respectively. [ABSTRACT FROM AUTHOR]

In this study, the perovskite layers were prepared by two-step wet process with different CH3NH3I (MAI) concentrations. The cell structure was glass/FTO/TiO2-mesoporous/CH3NH3PbI3 (MAPbI3)/spiro-OMeTAD/Ag. The MAPbI3 perovskite films were prepared using high and low MAI concentrations in a two-step process. The perovskite films were optimized at different spin coating speed and different annealing temperatures to enhance the power conversion efficiency (PCE) of perovskite solar cells. The PCE of the resulting device based on the different perovskite morphologies was discussed. The PCE of the best cell was up to 17.42%, open circuit voltage of 0.97 V, short current density of 24.06 mA/cm2, and fill factor of 0.747. [ABSTRACT FROM AUTHOR]

Sputtering made ZnO thin film was used as an electron-transport layer in a regular planar perovskite solar cell based on high quality CH3NH3PbI3 absorber prepared with a two-step spin-coating. An efficiency up to 15.9% under AM 1.5G irradiation is achieved for the cell based on ZnO film fabricated under Ar working gas. The atmosphere of the sputtering chamber can tune the surface electronic properties (band structure) of the resulting ZnO thin film and therefore the photovoltaic performance of the corresponding perovskite solar cell. Precise surface engineering of ZnO thin film was found to be one of the key steps to fabricate ZnO based regular planar perovskite solar cell with high power conversion efficiency. Sputtering method is proved to be one of the excellent techniques to prepare ZnO thin film with controllable properties. [ABSTRACT FROM AUTHOR]

A series of nonpolar antisolvents (chlorobenzene, bromobenzene, iodobenzene and toluene) were used to assist in the formation of smooth and crystalline CH 3 NH 3 PbI 3 thin films by a one-step spin-coating method. The structural, optical and excitonic characteristics of the resultant CH 3 NH 3 PI 3 thin films were analyzed using an atomic-force microscope, X-ray diffractometer, absorbance spectrum, photoluminescence (PL) spectrum, time-resolved PL and temperature-dependent PL. The properties of the CH 3 NH 3 PbI 3 thin films are dependent on the relative polarity and boiling point of the nonpolar antisolvents used in the washing treatment process. The interplay between nucleation (relative polarity) and crystal growth (boiling point) during the formation of CH 3 NH 3 PbI 3 thin films influences the short-circuit current density (J SC ) and power conversion efficiency (PCE) of the corresponding solar cells. The experimental results demonstrate that iodobenzene can be substituted for toluene as a more efficient antisolvent in the washing treatment process during the fabrication of CH 3 NH 3 PbI 3 thin films. In addition, it is predicted that the J SC and PCE can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

A phase-pure mixed-organic-cation perovskite absorber (MOC-PA) was fabricated by a one-step spin-coating process with a toluene washing treatment, and the structural, optical and excitonic properties of the resultant MOC-PAs were then characterized by scanning electron microscopy, X-ray diffractometry, absorbance spectrometer, and time-resolved photoluminescence. The averaged power conversion efficiency (PCE) of inverted phase-pure MOC-PA based photovoltaics could be improved from 12.21% to 13.28% by tailing the surface roughness of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin film from 1.43 nm to 1.84 nm. The improved PCE is mainly due to the increased short-circuit current density ( J SC ) which is attributed to the improvement of the exciton dissociation, as confirmed by photoluminescence experiments. In addition, the experimental results indicate that the PCE can be further improved by increasing the crystallinity of MOC-PAs. [ABSTRACT FROM AUTHOR]

Comprehensive studies were carried out to understand the thickness effects of ZnO thin films for tri-iodide perovskite absorber (TPA) based photovoltaics, including the absorption spectrum, photoluminescence, nanosecond time-resolved photoluminescence (NTRPL), and photo-induced absorption (PIA) of TPA/ZnO/ITO/glass. These were carried out in order to explore the Urbach energy of TPA films and the exciton dissociation at the interface between TPA and ZnO. The results show that the thickness of the ZnO thin film significantly influences the photovoltaic performance in terms of open-circuit voltage ( V OC ), fill factor (FF), and short-circuit current density ( J SC ). In the case of the thicker ZnO film, the photovoltaics have the better FF and V oc , as a result of the smaller electron recombination. This means that a thicker ZnO film can block the electron recombination from the Fermi level of the ITO to the valance band of the TPA. On the other hand, the thicker ZnO film results in a higher J SC due to the better exciton dissociation at the interface between TPA and ZnO, which means that the electron mobility of the thicker ZnO is higher. Consequently, the photovoltaic performance can be expected to be improved by using a transparent cathode electrode with high conductivity and electron mobility. [ABSTRACT FROM AUTHOR]

All inorganic perovskite quantum dots (PQDs) and perovskite CsPbX 3 /SiO 2 nanocomposites (PNCs) have shown their potentials for optical and lighting applications. We demonstrate a one-step approach to synthesize PQDs and PNCs more simply and effectively at room temperature in the open air. The resulting PNCs can show a narrow emission in the PL spectra and high stability under ambient conditions. In particular, both green CsPbBr 3 /SiO 2 and red CsPbI 3-x Br x /SiO 2 PNCs can be obtained by employing this easy and low-cost method. Even, the SiO 2 protection can also effectively prevent the halide exchange reaction between green and red PNCs, meaning the capability for white light applications. The resulting white light-emitting diodes (WLEDs) based on the green and red PNCs coated on the blue LED have a white Commission Internationale del' Enclairage (CIE) coordinates of (0.375, 0.362) and a low correlated color temperature (CCT) of 4054 K. [ABSTRACT FROM AUTHOR]