It is still a challenge to fabricate a smooth, high-quality perovskite film under ambient conditions via an inkjet printing process. Here, we report a systematic study of the fabrication of one-step inkjet-printed metal halide perovskite (IJP-MHP) films under ambient conditions. An inkjet-printed perovskite film with full surface coverage and large columnar grains was obtained through in situ heat treatment, self-vapor annealing (self-VA), and solvent engineering. An efficiency of 13.44% was achieved for the perovskite solar cell (PSC) with an architecture of FTO/IJP-SnO x /IJP-MHP/IJP-spiro-OMeTAD/Au. Furthermore, an ink additive polyvinylpyrrolidone (PVP) and antisolvent extraction treatment were carried out to retard perovskite nucleation and grain growth. Resulting perovskite films with improved film morphology and uniformity were obtained, although they delivered no competitive performance. Further optimization can be conducted to improve efficiency by careful selection of ink additives.

The primary challenge for the commercialization of hybrid perovskite solar cells (PSCs) is their chemical and thermal instability as compared to Si devices. Herein, we demonstrate that PSCs spray-coated with polystyrene retain 80% of their efficiency after 40 hours immersed in water or at 95 degrees C.

Microporous organic polymers that have three-dimensional connectivity stemming from monomers with tetrahedral or tetrahedron-like geometry can have high surface areas and strong fluorescence. There are however few examples of such polymers based on hindered biaryls, and their fluorescence has not been studied. Hypothesizing that the contortion in a hindered biphenyl moiety would modulate the optical properties of a polymer built from it, we synthesized a meta-enchained polyphenylene from a 2,2',6,6'-tetramethylbiphenyl-based monomer, in which the two phenyl rings are nearly mutually perpendicular. The polymer was microporous with S-BET = 495 m(2) g(-1). The polymer absorbed near-UV light and emitted blue fluorescence despite the meta-enchainment that would have been expected to break the conjugation. A related copolymer, synthesized from 2,2',6,6'-tetramethylbiphenyl-based and unsubstituted biphenyl-based monomers, was microporous but not fluorescent.

The pursuit of p-type semiconductors has garnered considerable attention in academia and industry. Among the potential candidates, copper iodide (CuI) stands out as a highly promising p-type material due to its conductivity, cost-effectiveness, and low environmental impact. CuI can be employed to create thin films with >80% transparency within the visible range (400–750 nm) and utilizing various low-temperature, scalable deposition techniques. This review summarizes the deposition techniques for CuI as a hole-transport material and their performance in perovskite solar cells, thin-film transistors, and light-emitting diodes using diverse processing methods. The preparation methods of making thin films are divided into two categories: wet and neat methods. The advancements in CuI as a hole-transporting material and interface engineering techniques hold promising implications for the continued development of such devices.

Planar perovskite solar cells (PSCs) based on low-temperature solution-processed SnO<inf>2</inf> electron transport layers (ETLs) usually suffer from energy losses within SnO<inf>2</inf> ETLs or at SnO<inf>2</inf>/perovskite interfaces. Doping is an effective strategy to modify the properties of SnO<inf>2</inf> and reduce such energy losses. Herein, Ce ions are incorporated into solution-processed SnO<inf>x</inf> and Ce-doped SnO<inf>x</inf> ETLs are fabricated for planar PSCs via inkjet printing. The Ce-doped SnO<inf>x</inf> ETL shows enhanced conductivity and improved energy level alignment with the perovskite layer, which can facilitate charge extraction and transport capabilities. Ce doping also effectively passivates the surface defects of SnO<inf>x</inf>. The photoluminescence characterization reveals that the carrier recombination is suppressed within the perovskite film. As a result, an improved power conversion efficiency (PCE) of 15.77% is obtained for the planar PSC with a Ce-doped SnO<inf>x</inf> ETL, compared to that of 14.66% for the undoped device. Furthermore, this work demonstrates a sustainable fabrication method which has great potential for the upscaling of PSCs.

This paper reports the solid-liquid phase equilibria of the CoSO4-H2O and CoSO4-H2SO4-H2O systems at low temperatures. Binary and ternary phase diagrams, including the stable solid phases CoSO4·6H2O and CoSO4·7H2O were established using experimental data and thermodynamic modeling applying the mixed-solvent electrolyte (MSE) model. The results showed that the addition of H2SO4 shifts the eutectic temperature and concentration to lower values for cobalt sulfate and ice crystallization. The trends obtained from the experimental data and the modeling are consistent for the binary CoSO4-H2O system with good agreement, but the ternary CoSO4-H2SO4-H2O system shows some deviations. In general, the MSE model is shown to be reliable for inferring and establishing the phase diagram of the low-temperature system. The phase diagrams are helpful for designing the pathways of cooling crystallization and eutectic freeze crystallization and assessing the performance of the low-temperature crystallization process in the production of CoSO4 hydrates. In addition, some practical examples of cooling crystallization and eutectic freeze crystallization of CoSO4 solutions are provided.

Reactive flash sintering (RFS) enables the simultaneous synthesis and sintering of ceramics and has been shown to affect the reaction pathway of different materials. Herein, in situ synchrotron X-ray diffraction (XRD) is used to investigate the (Mg,Ni,Co,Cu,Zn)O entropy-stabilized oxide formation during: (i) conventional heating and (ii) RFS under current rate-controlled mode. The same reaction pathway is verified in both instances: the starting rock-salt (RS), spinel (Co₃O₄), tenorite (CuO), and wurtzite (ZnO) phases transform into a single RS phase with a (1 1 1) to (2 0 0) intensity ratio of 0.67, consistent with a random distribution of the cations into the structure. Pt lattice peak shift from the XRD patterns is used as standard to monitor the sample surface temperature, revealing a strong endothermic reaction during the RS single-phase formation (Pt peaks shift toward higher angles while increasing sample temperature/current density). In RFS, the single-phase RS structure is formed in just 60 s at a furnace temperature of 600°C and a current rate of 220 mA mm⁻²/min. Therefore, RFS greatly accelerates the synthesis of (Mg,Ni,Co,Cu,Zn)O, however, it does not play a role in the reaction pathway for this material formation.

Significant interest exists in water-tolerant 2D lead iodide perovskites owing to their stability and proven potential in photovoltaic and photonic applications. These materials have solid-state phase transitions that are accessible below 100 °C. Here, the study witnesses the multiple phase transitions of the last members of a series of organic–inorganic hybrid materials, [(CnH2n+1NH3)2PbI4], with even n as n = 14, 16, and 18, once again. By employing temperature-dependent steady-state photoluminescence (PL) and temperature-dependent time-resolved photoluminescence (TRPL) spectroscopy in the temperature range of −18 to +90 °C and at −196 °C, we explore the thermal responses of these materials. The investigation reveals reversible phase transitions occurring between room temperature (RT) and elevated temperatures, impacting the optical properties and emitting colors of the perovskite compounds. The longer the alkyl chain, the higher the phase transition temperature, attributed to increased conformational disorder and enhanced perovskite symmetry. The decay constants for all compounds are very close in value, which confirms the underlying excited-state dynamics, pointing to contributions primarily from inorganic components across different phases. We anticipate that our results on the detection of phase transitions in 2D perovskites will not only motivate the use of these techniques for detecting phase transitions but also would help to understand their excited states in more details to selectively use them for solar cell and next-generation display technologies.

Efficiency and stability are the two most important factors in commercially scalable solar cells. In spite the high-power conversion efficiencies (PCE), the commercialization of perovskite solar cells (PSC) has been limited due to their low stability under ambient conditions. Environmental factors like moisture, heat, and light can all adversely affect PSC performance and limit device lifetime. In this review, we refer to the literature addressing the moisture induced stability issue of perovskite based solar cells. We present an overview on the moisture stability of the perovskite solar cells and clarify the effect of moisture on different layers in perovskite solar cells and the corresponding degradation process. Then we extend the discussion highlighting the strategies to prevent the moisture induced degradation in hybrid perovskite solar cells. The methods include composition engineering (cation and halide engineering) and interfacial layer engineering/surface passivation. We further summarize the utilization of doping techniques and use of organic/Inorganic passivators. We address methods of producing moisture stable 2D perovskites and admixtures of 2D and 3D perovskites. Lastly, the review highlights research directions focused on improving perovskite stability without compromising power conversion efficiency.

Crystallization of cobalt sulfate within a typical hydrometallurgical process for the recycling of Ni-Mn-Co oxide or Ni-Co-Al oxide Li-ion batteries has been investigated. The cobalt sulfate salt was obtained by eutectic freeze crystallization (EFC) from a synthetic acidic cobalt strip liquor after solvent extraction. The ternary phase diagram of CoSO4–H2SO4–H2O was first established by the mixed-solvent electrolyte (MSE) model to predict and reveal the changes in the system during the freezing process and to assess the conditions required for EFC. Batch EFC experiments were then conducted for the cobalt strip liquor, which contained a low concentration of impurities. It is shown that with suitable control of supersaturation, seeding, and stirring, pure ice and salt crystals can be recovered as separate phases at the eutectic temperatures, with the crystalline salts in the form of a heptahydrate. The crystallization process can be described using the ternary phase diagram, but with certain deviations. The deviations might be related to insufficient data at the low temperatures in the MSE model and acid entrapment in crystals during the crystallization process. Finally, the performance of the EFC process has been compared to that of an evaporative crystallization (EC) using the same strip liquor. It was found that the CoSO4·7H2O product obtained by EFC was of slightly higher quality considering purity and crystal shape compared to that from EC.