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Organic–inorganic perovskite (OIP) nanoparticles exhibit excellent luminescence properties and photovoltaic efficiency and can be used in bulk and thin films. In this study, a mechanically robust OIP quantum dot dispersion layer was deposited on glass substrates via a rapid synthesis process. First, hierarchical nanoporous structures with a thickness of 1.5 μm were formed on the glass surface. These structures were dipped in a precursor liquid and then dried. Thereafter, OIP crystals of methylammonium lead bromide (MAPbBr 3) with sizes of 5–10 nm were precipitated inside nanopores. The low-temperature luminescence properties of the obtained samples at 4–110 K were compared with those of spin-coated films and bulk MAPbBr 3. The emission peak wavelength of the sample precipitated in the nanopores on the glass surface (with an energy of 2.16 eV) was lower than that of the bulk sample (with an energy of 2.01 eV), and its luminescence intensity was two orders of magnitude higher than that of the bulk sample. The proposed method can be used to fabricate solar cells, electroluminescent devices, and scintillators. [ABSTRACT FROM AUTHOR]

• Time-resolved Scanning Electron Microscopy dynamically maps surface photovoltages. • Reversible photo-induced polarization of MAPbI3 films. • Sub-damage threshold conditions for optical and electronic excitation in MAPbI3. • Boundary condition dependence in light-assisted secondary electron contrast imaging. We introduce laser-assisted Time-Resolved SEM (TR-SEM), joining Scanning Electron Microscopy and laser light excitation, to probe the long-term temporal evolution of optically excited charge distributions at the surface of Metal Ammonium Lead Triiodide (MAPbI 3) hybrid perovskite thin films. Laser-assisted TR-SEM relies on the optically induced local modification of Secondary Electron (SE) detection yield to provide mapping of photoexcited potentials and charge dynamics at surfaces, and qualifies as a complementary approach to near-field probe microscopies and nonlinear photoemission spectroscopies for photovoltage measurements. Real-time imaging of evolving field patterns are provided on timescales compatible with SEM scanning rates, so that temporal resolution in the millisecond range can be ultimately envisaged. MAPbI 3 is an outstanding light-sensitive material candidate for applications in solar light harvesting and photovoltaics, also appealing as an active system for light generation. In this work, the real time temporal evolution of optically induced SE contrast patterns in MAPbI 3 is experimentally recorded, both under illumination by a 405 nm blue laser and after light removal, showing the occurrence of modifications related to photoinduced positive charge fields at surface. The long term evolution of these surface fields are tentatively attributed to ion migration within the film, under the action of the illumination gradient and the hole collecting substrate. This optical excitation is fully reversible in MAPbI 3 over timescales of hours and a complete recovery of the system occurs within days. Permanent irradiation damage of the material is avoided by operating the SEM at 5 keV of energy and 1–10 pA of primary current. Optical excitation is provided by intense above-bandgap illumination (up to 50 W/cm2). TR-SEM patterns show a strong dependence on the geometry of SE collection. Measurements are taken at different axial orientations of the sample with respect to the entrance of the in-column detection system of the SEM and compared with numerical modeling of the SE detection process. This enables to single out the information regarding the local potential distribution. Results are interpreted by combining data about the spectral distribution of emitted SEs with the configuration of the electric and magnetic fields in the specimen chamber. The present modeling sets a robust basis for the understanding of photoinduced SE electron contrast. [ABSTRACT FROM AUTHOR]

Highlights • Resistive switching behaviours in ITO/CH 3 NH 3 PbI 3 /metal memory devices. • Variation of metal contacts using Al, Ag, and Au. • Resistive Random Access Memory behaviour using Al as metal contact. • Write-Once-Read-Many characteristics in Ag and Au metal contacts. Abstract The utilization of defects in organic-inorganic hybrid perovskite materials such as CH 3 NH 3 PbI 3 is beneficial for memory applications. In this work, a simple CH 3 NH 3 PbI 3 memory device with various commonly used electrodes such as aluminium (Al), silver (Ag), and gold (Au) yielded different switching behaviours. Using Al in ITO/CH 3 NH 3 PbI 3 /Al device reveals Resistive Random Access Memory (ReRAM) behaviour with a SET voltage of 4.5 V and can be RESET by applying a negative sweep voltage above 1.3 V due to the formation of iodide vacancy filament. Interestingly, by using Ag and Au cathodes to replace Al, yielded Write-Once-Read-Many (WORM) resistive switching characteristics. The conversion process from OFF to ON occur at around 4.7 V and 4.0 V for Ag and Au, respectively. The "shorting effect" remains even though a reverse voltage was applied indicating data retention. These fabricated devices could contribute to further understanding of selecting the right electrodes and open up new possibility of studies in the direction of resistive switching memory applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The stability is improved due to the doping of lighter atoms. • Distinct blueshift implied reduction of optical properties in mixed structures. • Different doping positions in same phases are considered. • CH 3 NH 3 Pb(I 0.75 Br 0.25) 3 was chosed as the most potential optical material. Abstract Recently, extensive studies have widely fabricated and demonstrated that organic-inorganic hybrid perovskite-type solar cells, CH 3 NH 3 PbI 3 , have the superior optoelectronic properties. We explore the structural, electronic, optical properties and stability of tetragonal phase mixed halide perovskites CH 3 NH 3 Pb(I 1-y X y) 3 (X = Cl, Br; y = 0, 0.25, 0.5, 0.75), using first-principles calculations. The calculation of electronic structure reveals that the valance band maximum is governed by the halide p -orbitals and Pb 6 s -orbitals while the conduction band minimum formed by the mixed contribution from the p orbitals of Pb atom and s orbitals of I atom. For the stability and optical properties of CH 3 NH 3 Pb(I 1-y X y) 3 , the absorption coefficients show a blueshift of the absorption onsets but their stabilities show gradually increase with the increasing of X contents. Three different doping occupation phases of MAPb(I 0.5 X 0.5) 3 demonstrate that the impact of doping positions in linear optical property cannot be neglected but there is no change in stability. On the basis of all calculated results, we conclude that the best accouplement between absorption coefficiency and stability can be achieved at y = 0.25 in CH 3 NH 3 Pb(I 1−y Br y) 3 perovskites. [ABSTRACT FROM AUTHOR]

The power conversion efficiency of organic–inorganic halide perovskite solar cells has exceeded 20% because of the outstanding properties of perovskite materials. However, the practical application of perovskite solar cells is hindered by their poor stability, which is related to the ion transport properties of perovskite materials. In this study, we explore an effective approach for reducing the migration of ions and improving the stability of solar cells by using mixed organic–inorganic perovskites. The structural and electronic properties of the mixed halide perovskites, namely, FMRCPbI and FMRCPbI, with various cation vacancies ( V MA ' , V FA ' , V Cs ' , and V Rb ' ) and the organic cation migration effects of MAPbI 3 , FAPbI 3 , and mixed FMRCPbI 3 perovskites were investigated using first-principles method. FA cations exhibit high activation energy in the mixed FMRCPbI perovskite, suggesting that the diffusion of FA cations in FMRCPbI mixed perovskite is suppressed. In addition, radiation recombination is slightly small in FMRCPbI with a high concentration of cation vacancies due to the absence of energy levels of vacancy defects in the band gap. With its relatively low recombination loss and direct band gap with high absorption coefficient and high thermal stability, FMRCPbI mixed perovskite may be a new generation of highly efficient and emissive perovskites for photovoltaics and photoemission applications. [ABSTRACT FROM AUTHOR]

We present the preparation and characterization of solution processed lead free films of zero-dimensional methylammonium iodo bismuthate (CH 3 NH 3 ) 3 Bi 2 I 9 perovskite. Structural characterization reveals the formation of hexagonal micro-crystals with preferred growth orientation along the c -axis. The material exhibits a wide band gap of 2.9 eV and upon optical excitation the photoluminescence emission is observed at 1.65 eV (751 nm). Photoelectron spectroscopy confirms the stoichiometry of the (CH 3 NH 3 ) 3 Bi 2 I 9 perovskite and yields an ionization energy of 6.24 eV, while Raman spectra confirm the vibrational modes of the bioctahedral inorganic anion framework (Bi 2 I 9 ) 3− in the low wavenumber regime (<200 cm −1 ) regime. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) are employed to evaluate the experimental results. We apply this novel bismuth-based hybrid perovskite in proof of principle simple heterojunction solar cell devices, which yield power conversion efficiencies of ~0.1%. Further enhancement is expected once the film morphology and device stack are optimized. [ABSTRACT FROM AUTHOR]

We demonstrate that double spin coating, where a perovskite film is covered with another perovskite film, can increase substrate coverage from 81% to 97% along with an increase of film thickness from 151 ± 17 to 246 ± 18 nm. The increased substrate coverage by double coating improves the solar power conversion efficiency from 7.1 ± 0.6 to 10.3 ± 1.0%, an approximate 1.5-fold increase. Additionally, a double-coated film of higher substrate coverage exhibits amplified spontaneous emission (ASE) while a single-coated film of lower substrate coverage does not exhibit ASE. Double coating is an attractive method for increasing substrate coverage and improving solar power conversion and ASE. [ABSTRACT FROM AUTHOR]

To improve the electroluminescence efficiency of organic-inorganic hybrid perovskite (OIP) films, we need to consider several different types of post-treatments after film formation such as thermal annealing and solvent annealing. Here, we only applied thermal treatment on the film excluding all the other treatments. Then, we analyzed the effects of annealing time t ann on crystallinity of methylammonium lead bromide (CH 3 NH 3 PbBr 3 ) films and on luminous efficiency of CH 3 NH 3 PbBr 3 -based perovskite light-emitting diodes (PrLEDs). When thermal annealing of CH 3 NH 3 PbBr 3 films was conducted at 90 °C, t ann ≤ 10 min increased its crystallinity by eliminating residual solvent and completing the conversion of precursor to crystal, but t ann > 10 min reduced crystallinity and caused slight sublimation of CH 3 NH 3 Br. This was consistent with trend of the luminous efficiency of our PrLEDs that showed the optimum performance at t ann = 10 min. These results demonstrate that optimizing t ann of CH 3 NH 3 PbBr 3 films is a simple way to improve the luminous efficiency of PrLEDs by controlling their crystallinity. [ABSTRACT FROM AUTHOR]

In this paper, we present a study of the structural and optical properties of organic–inorganic halide-based perovskite semiconductors with band gaps varying from NIR to visible at room temperature. Thin films of nanocrystalline CH 3 NH 3 PbI 3 with different concentrations of methylammonium iodide (MAI) have been successfully deposited onto glass substrates using single step spin-coating technique. The prepared films have been characterized by X-ray diffraction, optical absorption spectroscopy and photoluminescence measurements. X-ray diffraction scans revealed that even for stoichiometric atomic concentrations of MA:Pb:I of 1:1:3, the PbI 2 phase was also present. The PbI 2 phase showed a highly textured along the (001) direction in all the prepared films, with a crystallite size in the range of approximately 30–40 nm. The optical absorbance edge of CH 3 NH 3 PbI 3 thin films is described in terms of direct transition model proposed by Tauc in the strong absorption region. The band gap of the pure PbI 2 film was calculated to be 2.40 eV, whereas the band gap of the pervoskite film with stoichiometric ionic ratio of 1:1 PbI 2 and CH 3 NH 3 I was calculated to be 1.46 eV, while absorption coefficient is ~10 5 cm −1 . Photoluminescence measurements showed a red shift in the perovskite emission with increasing the MAI concentration, confirming the correct placement of the MA ions in the perovskite crystalline structure showing the PbI 2 octahedra. Our results confirm the existence of PbI 2 phase in the highly efficient perovskite solar cells, as demonstrated in the recent publication. [ABSTRACT FROM AUTHOR]

In this paper luminescent solar concentrators (LSCs) based on CH 3 NH 3 PbBr 3 perovskite quantum dots (QDs) and QDs containing gold nanoparticles (NPs) with flat and half-cylindrical geometries are introduced. Excitonic and PL emission peaks at 512 nm and 539 nm with majority average size of 16 nm are the characteristics of the synthesized lead bromide perovskite QDs. Incorporation of synthesized spherical gold NPs with an average diameter of 13 nm and absorption peak at 527 nm in perovskite based LSCs are also investigated. The measured reabsorption loss is decreased for LSCs in the presence of gold NPs. The PCE of edge-mounted solar panel in sheet LSCs based on gold NPs doped QDs, is enhanced with respect to CH 3 NH 3 PbBr 3 QD based LSCs, due to plasmonic effect of gold NPs. Varying the LSC geometry to half-cylinder improves the device performance by effectively concentrating of incident light into the solar panel. The effect of backscatterers is also investigated for bottom-mounted solar panel in new half-cylindrical geometry. The best device efficiency is obtained for the white backgrounded LSC, since it could act as a scatter to send back the lost light into the LSC, efficiently. [Display omitted] • Lead bromide based Luminescent solar concentrators (LSCs) are fabricated in flat sheet and novel half-cylindrical geometries. • Doping Au NPs to perovskite QDs decreases the reabsorption and boosts the overall output power of LSC devices. • The PCE of half-cylindrical LSC devices are higher than sheet LSCs, due to the lens-like behavior of half-cylinders. • The white back scatterer improves the efficiency of half-cylindrical LSC devices more than mirror and black scatterers. [ABSTRACT FROM AUTHOR]

Perovskite-structured organic–inorganic materials such as CH 3 NH 3 PbI 3 are attracting much interest in the scientific community because of their abilities to function as revolutionary light harvesters and charge transfer materials for solar cells. To achieve high power conversion efficiency (PCE), it is critical to optimize the perovskite film layer. This paper reports the temperature and concentration controls on the two-step solution process. A diffusion-controlled growth mechanism is proposed for this process in tuning the morphology and purity of the perovskite film, which are proven to be important factors contributing to the photovoltaic performance. The highest PCE of 11.92% is achieved with an optimized perovskite crystal size of ∼150 nm and an appropriate amount of residual PbI 2 . This study sheds light on the design and fabrication of highly efficient, low-cost, solution-processed perovskite solar cells. [ABSTRACT FROM AUTHOR]

The Luminescent solar concentrators (LSCs) consist of a film containing optically active centers, converting part of the absorbing radiation into a specific emitting wavelength, when exposed to sunlight. The emitting centers are also crucial factors regarding their efficiency, so the selection must be done carefully. Here, we introduce organometal halide perovskite as a new class of phosphors, to use in luminescent solar concentrators. The coating of a Si PV cell with an organometal halide perovskite is tested. The obtained results reveal that, to find a suitable condition for effective LSC, it is necessary to determine appropriate molar ratio of organic and inorganic portion in synthesis perovskite, as well as concentration of halide perovskite in LSC. It is found that CH 3 NH 3 PbBr 3 perovskite with the CH 3 NH 2 /PbBr 2 : 6/1 M ratio and 7.0 wt% perovskite concentration in Polyvinyl Alcohol (PVA) leads to the highest efficiency (increased about 45%, compared to uncoated cell). [ABSTRACT FROM AUTHOR]

Perovskite-sensitized nanoporous TiO 2 films with different thicknesses are prepared by an in situ method, which are employed as photoanodes in perovskite solar cells (PSCs). The photoelectrochemical properties of different photoanodes are quantified by the ultraviolet to visible reflectance spectra, incident monochromatic photon-to-current conversion efficiency, and electrochemical impedance spectroscopy measurements. Results demonstrate that the thin photoanode has high electron lifetime for recombination, which can enhance the separation and transmission of the electron and hole. However, the sunlight utilization will decrease with reducing the photoanode thickness due to the small quantity of CH 3 NH 3 PbI 3 filled into the photoanode to absorb sunlight. After optimization, PSC with 0.80 μm of the photoanode thickness shows a superior cell efficiency of 12.22% without a hole transporting material. [ABSTRACT FROM AUTHOR]

Toxic elements such as lead, instability, and low efficiency are some of the challenges of producing organic-inorganic solar cells. In this research, methylammonium Sn-based halide perovskite (MASnI 3) with less toxicity and a normal structure was modeled. The simulated cell configuration consisted of FTO / PC 61 BM / MASnI 3 / PEDOT : PSS + WO 3 / Cu layers. In this research, water-free poly(3,4-ethylenedioxythiophene): poly styrene sulfonate (PEDOT: PSS) and tungsten trioxide (WO 3) nanoparticles were used as the hole‐transport layer (HTL) and phenyl- C 61 -butyric acid methyl ester (PC 61 BM) as the electron-transport layer (ETL). This research investigated the effects of variation in the device parameters of some layers on the performance parameters and determined the optimal value for each layer to improve power conversion efficiency (PCE). In another structure, the absorber layer was replaced with formamidinium tin iodide-based perovskite (FASnI 3), and after finding the optimal values for the device parameters, the results were compared with the previous structure. The comparison results indicated that the structure with FASnI 3 outperforms MASnI 3. The simulations were conducted in the SCAPS-1D environment. The optimal results obtained from the structure with FASnI 3 -based perovskite after optimizations were as follows: short-circuit current density (J SC) of 24.65 mA / cm 2 , open-circuit voltage (V OC) of 1.12 V, fill factor (%FF) of 86.02%, and PCE of 23.69%. • A water-free PEDOT was studied. • The effect of increasing the doping concentration was investigated. • Effects of the absorber layer with formamidinium-based perovskite (FASnI 3), was investigated. • High performance solar cell was obtained by optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonication synthesis of lead deficient MAPb1 -x Zn x Br 3 PQDs. • High PLQY > 93% for Zn doped MAPbBr 3 in open atmosphere. • Variation of Zn concentration in MAPbBr 3 for the first time. • Incorporation of Zn2+ ions improves the stability. • Demonstration of warm white LED prototype with 124% color gamut. B-site substitution perovskite quantum dots (PQDs) with amended stability and less toxicity have been acquainted in recent years. However, the PQDs comprising various B-site cations display low photoluminescence quantum yields (PLQYs), instability, and require skimpy synthesis procedure. Herein, we have endeavored to introduce ultrasonication synthesis of MAPb1 -x Zn x Br 3 PQDs as an auspicious route to stable PQDs with enhanced PLQY. The successful synthesis of PQDs resulted in a high PLQY (>93%), which is supposed to be owing to the decrease in non-radiative recombination centers. Furthermore, we have found that the structure, morphology, and emission properties are secured with the substitution of Zn2+. The PQDs have been integrated as color converting layers coated on blue light emitting diode (LED) chips, which exhibit white light with the wide color gamut of National Television Standards Committee (NTSC) 124%. The present research reveals a new synthesis route to obtain stable and efficient PQDs without negotiating color quality for display application. [ABSTRACT FROM AUTHOR]

• Schematic drawing of the CH3NH3PbI3-xClx/GaN microwire array heterostructures photodetector. • Characterization of the CH3NH3PbI3-xClx/GaN microwire array photodetector. • Photoelectric performance compared to the hybrid three types of photodetectors from ultraviolet to visible light region. • I-V curves with or without perovskite layer measured in the dark and under 325 nm light irradiation. • The mechanism to improve the performance of heterostructure photodetector was discussed In recent years, the combination of perovskites with other materials to improve the photoelectric performance has received widespread attention. In this work, we demonstrate a hybrid heterostructure photodetector with the combination of GaN microwire array and perovskite. Compared to perovskite and GaN microwire array photodetectors, the hybrid CH 3 NH 3 PbI 3- x Cl x /GaN microwire array photodetector exhibits more excellent photoelectric performances in a wide detection range from ultraviolet to visible. Under 325 nm laser irradiation, the hybrid photodetector generates a large photocurrent (1.04 ×10-5 A), a high on/off ratio (>104), a fast response time (raise time of 0.66 ms and decay time of 0.71 ms), and higher responsivity , detectivity. Meanwhile, when the perovskite is combined with the GaN microwire array, the device also has a higher photocurrent, on/off ratio, and faster photoresponse compared with the perovskite photodetector in the visible light region. This is interpreted as the effective separation photogenerated carriers at the hetero-interface, and the directional transfer of carriers within the one-dimensional GaN microwire array. This study sheds light on fabricating high-performance heterostructures photodetectors. [ABSTRACT FROM AUTHOR]

Herein, we reported the introduction of carbon nanodots (CNDs) and polyvinylidene fluoride (PVDF) as additives into perovskite CH 3 NH 3 PbI 3 through in situ synthesis to prepare PVDF-CH 3 NH 3 PbI 3 @CNDs composite, which demonstrated improved water tolerance and mechanical stability. The application of PVDF-CH 3 NH 3 PbI 3 @CNDs for photoelectrochemical sensing was then explored. A molecularly imprinted polymer (MIP) that could specifically recognize cholesterol (CHO) was anchored to PVDF-CH 3 NH 3 PbI 3 @CNDs via a simple thermal polymerization process, followed by elution with hexane. A label-free and sensitive photoelectrochemical method for CHO detection was achieved by using the MIPs@PVDF-CH 3 NH 3 PbI 3 @CNDs platform. The detection limit for CHO was 2.1 × 10−14 mol/L, lower than most of the existing CHO detection methods. In our perception, this platform can be extended to numerous other analytes. This research result may provide a new understanding to improve the performance and broaden the application range of organic-inorganic perovskites. Image 1 • Carbon nanodots and molecular imprinted polymers (MIPs) were both used to functionalize CH 3 NH 3 PbI 3. • The functionalized CH 3 NH 3 PbI 3 showed good aqueous stability and selectivity. • A novel PEC sensor for cholesterol was constructed based on the functionalized perovskites. [ABSTRACT FROM AUTHOR]

• Humidity is intensively impact the instability of hybrid organic-inorganic perovskites. • For unpacked device, symmetric hysteresis loop rotation converts from anticlockwise to clockwise. • For one-end packed device, hysteresis loops transform from anticlockwise symmetry to antisymmetry. • Modulable hysteresis is from the decrease of surface state and the formation of PbI2 and bulk defect. • Electrical field-triggered filling and emptying of traps dominate adjustable electric transport. The instability of hybrid organic-inorganic perovskites (HOIP) in environment, especially in high humidity causes different conductance that should be addressed to improve its large-scale application and development. Here, the electrical transport of an individual CH 3 NH 3 PbI 3 micro/nanowire-based two-terminal device with encapsulating different ends was investigated in a condensed water environment. For an unencapsulated device, linear I-V curve transforms first into two symmetrical counterclockwise hysteresis loops with positive resistive switching (RS) feature, and eventually converts into two symmetrical clockwise hysteresis loops with negative RS feature. For the device encapsulated at one end, the linear I-V curve first transforms into two symmetrical counterclockwise hysteresis loops with positive RS behavior, and then converts into two antisymmetric hysteresis loops with a bipolar RS feature. The origin of modulable hysteresis with different RS characteristics is mainly from the decomposition-induced decrease of surface states and formation of PbI 2 and structure defects. As a consequence, the electrical field-triggered filling and emptying of traps in different regions dominate the adjustable performance of electrical transport. The controllable electrical transport can not only demonstrate clearly that condensed water can promote the decomposition of CH 3 NH 3 PbI 3 , but also verify that the hysteresis behavior with different RS memory effect originate from the decomposition-induced traps. [ABSTRACT FROM AUTHOR]