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It is well-known that two-dimensional Ruddlesden-Popper (2DRP) perovskite has higher stability than three-dimensional counterparts. However, fundamental issues still exist in the vertical orientation and phase composition as well as phase distribution. Here, obvious control of the film quality of 2DRP PEA

Besides widely used surface passivation, engineering the film crystallization is an important and more fundamental route to improve the performance of all-inorganic perovskite solar cells. Herein, we have developed a urea-ammonium thiocyanate (UAT) molten salt modification strategy to fully release and exploit coordination activities of SCN- to deposit high-quality CsPbI3 film for efficient and stable all-inorganic solar cells. The UAT is derived by the hydrogen bond interactions between urea and NH4 + from NH4 SCN. With the UAT, the crystal quality of the CsPbI3 film has been significantly improved and a long single-exponential charge recombination lifetime of over 30 ns has been achieved. With these benefits, the cell efficiency has been promoted to over 20 % (steady-state efficiency of 19.2 %) with excellent operational stability over 1000 h. These results demonstrate a promising development route of the CsPbI3 related photoelectric devices.

Novel borosilicate glasses containing Tb3+/Eu3+ co-doped KY3F10 nanocrystals were manufactured via a traditional melt-quenching route and subsequent heat treatment. The nano-crystal structure was determined by X-ray diffraction (XRD) and its morphology directly observed by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Enhanced fluorescence intensity of the prepared samples can be obtained with a higher temperature heat treatment, which is ascribed to the embedding of Tb3+/Eu3+ co-doped KY3F10 nanocrystals in the system glass. The effect of Eu3+ concentration on its luminescence was also carried out, and the energy transfer process between Tb3+ and Eu3+ was ascertained through emission spectra and decay curves. It was found that tunable luminescence from green to red can be obtained by controlling Eu3+ concentration in view of red emission of Eu3+ ion and energy transfer process from Tb3+ to Eu3+. The fluorescence relative intensity ratio (FIR) between 545 nm (Tb3+: 5D4→7F5) and 615 nm (Eu3+: 5D0→7F2) in the sample was also highly dependent on the temperature of the environment from measured temperature-dependent spectra, and high sensitivity of 0.24% K-1 can be achieved for the obtained glass ceramics (GCs). Their excellent properties in both chemistry-physics and sensing behavior render them a promising candidate for multicolor display and temperature sensor.

All-inorganic CsPbI

In this work, a new small molecular material, 9,9'-(pyrene-1,6-diyldimethylylidene)bis[N,N,N′,N′-tetrakis(4-methoxyphenyl)-9H-fluorene-2,7-diamine] (PFD), as a hole-transporting layer was designed for perovskite solar cells (PSCs). PFD has a rigid and flat pyrene unit as the central building block and a symmetric structure to increase the conjugation degree for better carrier conductivity. A power conversion efficiency (PCE) of 18.6% was achieved for PSC based on undoped PFD. When spiro-OMeTAD is further introduced on the top of PFD (PFD/spiro-OMeTAD), a PCE of 21.02% was achieved with a steady-state efficiency of 19.92%, revealing that PFD as an interfacial layer could restrain carrier recombination. Unencapsulated devices based on PFD or PFD/spiro-OMeTAD exhibit excellent stability including long-term stability for over 1400 h under ambient condition, and moisture stability under the “Double 60 program” test simultaneously at 60% RH and 60 °C in air. Besides, no obvious degradation was found for the PFD/spiro-OMeTAD device over 200 h under continuous illumination at the maximum power point tracking (MPPT) in N2 atmosphere. It is thus suggested that PFD could be a promising dopant-free HTM for PSCs, and also acts as an interface layer to suppress the carrier recombination to further improve the device performance.

Currently, there is an urgent need to develop low-cost hole-transporting materials (HTMs) for inverted perovskite solar cells (PSCs), whose power conversion efficiency (PCE) is still inferior to th...

Summary Electrical transients enabled by an optical excitation and an electric detection provide a distinctive opportunity to study charge transport, recombination, and even photoelectric hysteresis of a solar cell in a wide time window ranging from nanoseconds to seconds. However, controversies on how to exploit these investigations to unravel the charge loss mechanism of the cell have been ongoing. Herein, a new methodology of quantifying the charge loss within the bulk absorber or at the interfaces and the defect properties of solar cells has been proposed. This methodology has been successfully applied in the study of commercialized silicon and emerging Cu2ZnSn(S, Se)4 and perovskite solar cells herein and should also be applicable to other similar photovoltaic device systems. Overall, this work provides an alluring route for a comprehensive investigation of dynamic physics processes and charge loss mechanism of solar cells and possesses potential applications for other optoelectronic devices.

In this study, a new p-type π-conjugated ladder-like polymer, poly(3,3′-(((2-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzol[1,2-b:4,5-b′]dithiophen-2-yl)-5-methyl-1,4-phenylene)bis(oxy))bis(hexane-6,1-diyl))bis(1,1,1,3,5,5,5-heptamethyltrisiloxane)) (P-Si), has been designed for SnO2-based perovskite solar cells. Our investigation reveals that this π-conjugated ladder-like polymer system decorated with hydrophobic alkyl chains and siloxane chains is likely the reason for the improvement in the surface morphology and crystallinity of the perovskite films, leading to reduced defect states and enhanced device stability. In addition, P-Si with a suitable highest occupied molecular orbital energy level (−5.41 eV) can act as a hole transport medium between the perovskite and spiro-OMeTAD to enhance the excellent hole transportation. As a result, power conversion efficiency (PCE) as high as 21.5% with 21.3% steady-state PCE was achieved. Typically, the device with P-Si can retain 98% of the original average PCE after being stored in an ambient environment with 20% relative humidity for 120 days, indicating its good long-term stability. Furthermore, after aging for 100 h under illumination at the maximum power point in a nitrogen atmosphere, the P-Si modified device retains over 98% of its initial performance.

Methylamine-free formamidinium-cesium (FA-Cs) lead halide has attracted wide interest for enhancing stability of perovskite solar cells; however, crystallization of FA-Cs perovskite usually suffers from more complicated intermediate phase transition processes. Herein, we have developed a dual-functional additive consisting of organic ammonium cation and dithiocarbamate anion to regulate the crystallization and defects of the FA-Cs perovskite film. With a synergistic contribution of the cationic and anionic groups, 24.5% efficiency (certified efficiency: 23.7%) has been achieved in a single cell with excellent operational stability. Under steady-state light illumination and bias voltage, 90% power output of its initial state can still be obtained after 500 h continuous operation. After enlarging the device from single cell to module, > 20.5% efficiency has been realized from a 10.6 cm2 minimodule by only using an ultralow-cost laser scribing technology. Briefly, this exploitation of cation-anion synergistic effect from dual-functional additives provides more opportunities for promoting the development of perovskite solar cells.

The stability issue hinders the commercialization of the perovskite solar cells (PSCs), which is widely recognized. The efficiency generally decreases over time during the working condition. Here, we report an efficiency enhancement phenomenon of PSCs in the stability test at the maximum power point, which is speculated to be related to the electric-field-induced ion migration. The defect density and efficiency-related parameters were traced in situ by admittance spectroscopy and transient photovoltage when the cell works under bias voltage. The performance enhancement was revealed to be attributed to the reduction of the cell defects owing to ion migration. An efficiency of 22.3% can be achieved after the bias voltage was kept for 8 h. These findings suggest that ion migration is a double-edged sword that affects the electrical stability of PSCs, which presents a potential approach to improve the device's stability by appropriately controlling the defect states.

All-inorganic mixed-halide perovskite thin films exhibit intriguing one- and two-photon absorption properties and optical stabilities. However, perovskite polycrystalline thin films prepared via conventional methods generally possess high trap densities, which reduces the efficiency of carrier transport. Thus, highly sensitive dual-mode photodetection in both the visible and near-infrared (NIR) regions is seemingly difficult to achieve. To overcome these issues, we utilized a spin-coating thermal-pressed (SCTP) strategy to grow CsPbI1.5Br1.5 QSC films with high crystallinity and a uniform orientation. The SCTP-grown films were found to be densely stacked with large single-crystal grains that vertically spanned the entire film thickness. The crystals were determined to be approximately 40 µm in diameter, which resulted from the removal of a significant number of grain boundaries and surface defects. The trap density of the SCTP-grown film was markedly decreased (ntrap: (8.55 ± 0.96) × 1011 cm–3), and it demonstrated a long carrier lifetime (τ2: 132.53 ± 9.45 ns) and a large two-photon absorption coefficient (β: 0.94 ± 0.04 cm·GW–1), all of which made the SCTP-grown CsPbI1.5Br1.5 QSC film superior to other reported CsPbI3−xBrx quantum dots and films. The visible and NIR dual-mode photodetection of the film at 532 and 1030 nm, respectively, was demonstrated with giant single-/two-photon responses. In addition, the surface nonlinear optics of the SCTP-grown QSC films were innovatively studied. This endowed the high-quality all-inorganic perovskite QSC films with optical properties beneficial for high-contrast photodetection necessary in application such as encryption imaging and high-efficiency solar cells.

All-inorganic perovskites have aroused great interest recently because of their prominent photoelectric properties and thermal stability for stable, highly efficient perovskite solar cells. Herein, a two-step multiple spin coating method has been developed for the first time to prepare cesium halide perovskite films. In particular, dimethyl sulfoxide (DMSO) is introduced into CsBr/methanol precursor solution to increase the solubility of CsBr; in the meantime, it can also remarkably influence the morphologies, optical properties and photovoltaic performance of CsPb(IxBr1−x)3 (0 < x < 1) films. By regulating the content of DMSO, as high as 13.27% power conversion efficiency (PCE) has been achieved with a steady-state PCE of 12.5% under optimal conditions, which can maintain 98% of the initial PCE for 480 h under ambient conditions without encapsulation. The synergistic effect of the solvent-engineering method can provide a new access for good quality all-inorganic perovskite thin films for high performance optoelectronic devices.

A series of novel oxyfluoride borosilicate glass ceramics (GCs) possessing KY3F10 crystalline phase co-doped fixed 0.3 mol% Bi3+ and various Eu3+ from 0 to 1.0 mol% were obtained from the system of SiO2–B2O3–K2O-YF3-KF-Bi2O3–Eu2O3 matrix glass. The emission of the GCs was effectively impacted by both the excitation wavelength and Eu3+ concentration. A tunable luminescence from blue to pink can be adjusted by change of Eu3+ concentration from 0 to 1 mol% under excitation of 280 nm for 0.3 mol% Bi3+/у mol% Eu3+ co-doped GCs, while from orange to pink by change of excitation wavelength from 260 to 300 nm for 0.3 mol% Bi3+/1 mol% Eu3+ co-doped GCs. The energy transfer (ET) process from Bi3+ to Eu3+ and the emissions of both Bi3+ and Eu3+ are mainly response for the tunable emission of the GCs. Referring to the fluorescence relative intensity ratio (FIR) between 412 nm (Bi3+:1S0→3P1) and 615 nm (Eu3+:5D0→7F2) determining from temperature-dependent spectra in a wide temperature range of 298–548 K, two crucial parameters of absolute sensitivity (Sa) and relative sensitivity (Sr) of the sample are estimated up to 1.82 % K−1 at 548 K and 3.84 % K−1 at 298 K, respectively. Such high optical temperature sensitivity, widely strong tunable emission and the excellent chemical physical properties endow the GCs a potential candidate for non-contact optical thermometry and multi-color display.

A series of Bi3+/Eu3+ co-doped Ba3Y(BO3)3 red-emitting phosphors were successfully prepared by the combustion method. The crystal structure and photoluminescence properties of the as-prepared phosphors were investigated by X-ray powder diffraction, photoluminescence excitation and emission spectra. In this paper, the Bi3+ ion was employed as a sensitizer to improve the red emission intensity of Eu3+. The optimal doping concentration of Bi3+ was 1 mol%. The observed excitation broad bands centered at 300 nm confirmed Bi3+ ion doped into the Ba3Y(BO3)3 host. The red emission intensity of Eu3+ was significantly enhanced by doping a small amount of Bi3+. Furthermore, Bi3+/Eu3+ co-doped phosphor possessed admirable thermal stability (the emission intensity of studied phosphor at 423 K maintained 80.7% of the initial intensity at room temperature). The results manifest that Bi3+ ion is an efficient sensitizer for Eu3+ ion and Ba3Y(BO3)3: 24 mol% Eu3+, 1 mol% Bi3+ phosphors possess a great potential for applications in white LEDs.

In perovskite solar cells, the halide vacancy defects on the perovskite film surface/interface will instigate charge recombination, leading to a decrease in cell performance. In this study, cadmium sulfide (CdS) has been introduced into the precursor solution to reduce the halide vacancy defects and improve the cell performance. The highest efficiency of the device reaches 21.62%. Density functional theory calculation reveals that the incorporated Cd2+ ions can partially replace Pb2+ ions, thus forming a strong Cd-I bond and effectively reducing iodide vacancy defects (VI); at the same time, the loss of the charge recombination is significantly reduced because VI is filled by S2- ions. Besides, the substitution of Cd2+ for Pb2+ could increase the generation of PbI2, which can further passivate the grain boundary. Therefore, the stability of the cells, together with the efficiency of the power conversion efficiencies (PCEs), is also improved, maintaining 87.5% of its initial PCEs after being irradiated over 410 h. This work provides a very effective strategy to passivate the surface/interface defects of perovskite films for more efficient and stable optoelectronic devices.

The photocatalytic reduction of CO2 over Ag/TiO2 composites prepared with a simple silver mirror reaction method was investigated under UV-visible irradiation in both gas-phase (CO2 + water vapor) and aqueous solution (CO2-saturated NaHCO3 solution) systems. The as-prepared Ag/TiO2 nanocomposite exhibits efficient photocatalytic activity due to the surface plasmonic resonance and electron sink effect of the Ag component, which was found to be closely related to the size and loading amount of Ag. The rapid silver method is effective at curbing the size of Ag, so photocatalytic activity can be improved. Diverse organic chemical products were detected, including mainly methane and methanol as well as a small amount of C2 and C3 species such as acetaldehyde and acetone. Possible photocatalytic mechanisms were proposed. This artificial photosynthesis process may give a prosperous route to the removal of CO2 while simultaneously converting CO2 to valuable fuels based on highly efficient photocatalysts.

On p. 2766, Qinshan Zhu and co-workers report on multishell hollow Cu2O microspheres that are synthesized by a facile and one-pot solvothermal route. A two-step organization process, in which hollow microspheres of Cu2(OH)3NO3 are formed first followed by reduction to Cu2O by glutamic acid, leads to the special multishell and hollow microstructures. Interestingly, a Cu2O gas sensor fabricated with the multishell microspheres shows a much higher sensitivity to ethanol than solid Cu2O microspheres. Hierarchical assembly of hollow microstructures is of great scientific and practical value and remains a great challenge. This paper presents a facile and one-pot synthesis of Cu2O microspheres with multilayered and porous shells, which were organized by nanocrystals. The time-dependent experiments revealed a two-step organization process, in which hollow microspheres of Cu2(OH)3NO3 were formed first due to the Ostwald ripening and then reduced by glutamic acid, the resultant Cu2O nanocrystals were deposited on the hollow intermediate microspheres and organized into finally multishell structures. The special microstructures actually recorded the evolution process of materials morphologies and microstructures in space and time scales, implying an intermediate-templating route, which is important for understanding and fabricating complex architectures. The Cu2O microspheres obtained were used to fabricate a gas sensor, which showed much higher sensitivity than solid Cu2O microspheres.