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High FF: in situ K-doped precursors make large-grain and void-free absorbers. The doping-enhanced Sn diffusion eliminates the local content vibration, suppresses deep level defects, and to higher cell efficiency with greatly improved FF.

Purpose Single-incision laparoscopic appendectomy (SILA) is usually performed using single-port instruments, which may restrict its development and application. This study explored the performance of transumbilical SILA (TSILA) and suprapubic SILA (SSILA) using only conventional laparoscopic instruments and compared them with conventional three-hole/port laparoscopic appendectomy (CLA). Methods This retrospective study included 174 patients who underwent CLA, TSILA, or SSILA for acute appendicitis at our hospital between June 2019 and July 2021. Demographic data and clinical outcomes were compared among the three groups. Results Compared with CLA, TSILA was associated with significant reductions in postoperative pain, length of hospital stay, and hospital cost, while SSILA was associated with significant reductions in length of hospital stay and hospital cost (all P P P = 0.039). Besides, compared with TSILA, SSILA showed significantly higher postoperative pain score (2 ± 2 vs 3 ± 2, P = 0.006). Mild incisional or intraabdominal infections were noticed in 2 (3.0%) patients in the CLA group, 3 (5.1%) in the TSILA group, and 3 (6.3%) in the SSILA group (P = 0.69). Conclusion SILA performed with only conventional laparoscopic instruments was associated with reduced hospital stay and cost and higher cosmetic satisfaction in comparison to CLA. However, it is technically demanding and may increase operative time.

Ultrabroadband photodetectors (PDs) working in the frequency range from the UV to THz regions of the spectrum play a crucial role in integrated multifunction photoelectric detection. Even so, a shortage of high-performance PDs has seriously restricted the overall development of this field. The present work demonstrates a high-performance, ultrabroadband PD with a composite nanostructure comprising a suspended carbon nanotube (CNT) film on which titanium and palladium are deposited. The application of titanium and palladium to the CNT film in this device provides n-doping and p-doping, respectively, and the deposited metal nanoparticles also ensure enhanced thermal localization. This device exhibits short response time, high responsivity, large linear dynamic range, and small noise equivalent power over the ultrabroadband spectrum based on a strong photothermoelectric effect. Numerical simulation results also confirm the effective doping and enhanced thermal localization in this PD resulting from the deposited metals. A theoretical analysis shows that the thermal conductivity of the composite film is no longer independent of the temperature over a wide temperature range. This work provides a simple but novel strategy for the design of high-performance ultrabroadband PDs.

The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target. The precursors are selenized in the H2Se-containing atmosphere to prepare (Ag,Cu)(In,Ga)Se2 (ACIGS) absorbers. The beneficial effects of Ag doping are demonstrated and their mechanism is explained. It is found that Ag doping significantly improves the films crystallinity. This is believed to be due to the lower melting point of chalcopyrite phase obtained by the Ag doping. This leads to a higher migration ability of the atoms that in turn promotes grain boundary migration and improves the film crystallinity. The Ga enrichment at the interface between the absorber and the back electrode is also alleviated during the selenization annealing. It is found that Ag doping within a specific range can passivate the band tail and improve the quality of the films. Therefore, carrier recombination is reduced and carrier transport is improved. The negative effects of excessive Ag are also demonstrated and their origin is revealed. Because the atomic size of Ag is different from that of Cu, for the Ag/(Ag + Cu) ratio (AAC) ≥ 0.030, lattice distortion is aggravated, and significant micro-strain appears. The atomic radius of Ag is close to those of In and Ga, so that the continued increase in AAC will give rise to the AgIn or AgGa defects. Both the structural and compositional defects degrade the quality of the absorbers and the device performance. An excellent absorber can be obtained at AAC of 0.015.

The surface roughness of CIGS absorber and residual Cu–Se phase on the surface are two major factors greatly affecting the performance of CuInGaSe2 (CIGS) solar cells with the absorbers fabricated by the selenization annealing of Cu–In-Ga precursors. In this work, Br2–CH3OH solution is used to etch the surfaces of CIGS films to address these two challenges. The effects of the etching treatment on CIGS films and devices are investigated. It is found that etching significantly reduces the film roughness and removes the Cu–Se phase. Thus, the performance of the device is improved within a certain range. In addition, it is found that CIGS films with suitable surface roughness effectively absorb incident light and possess a higher Jsc. However, excessive etching causes the film to be too thin, and the carrier recombination at the back electrode increases. Based on these characteristics, this work optimizes the Br2 etching process.

Carbon nanotube-silicon (CNT-Si) solar cells represent one of the alternative photovoltaic techniques with potential for low cost and high efficiency. Here, we report a method to improve solar cell performance by depositing conventional transitional metal oxides such as WO3 and establishing a collaborative system, in which CNTs are well-embedded within the WO3 layer and both of them are in close contact to Si substrate. This unique collaborative system optimizes the overall energy conversion process including the light absorption (antireflection by WO3), carrier separation (forming quasi p-n junction) and charge collection (CNT conductive network throughout the oxide layer). Combining with our previous TiO2-coating and HNO3-doping techniques, a solar cell efficiency of >18% at an active area of 0.09 cm2 (air mass 1.5, 100 mW/cm2) was achieved. The oxide-enhanced CNT-Si solar cells which integrate the advantages of traditional semiconductors and novel nanostructures represent a promising route toward next-generation high-performance silicon-based photovoltaics.

Enhancing the mechanical strength of highly conductive pure metals usually causes significant reduction in their electrical conductivity. For example, introducing phase/matrix interfaces or more grain boundaries, are common and effective methods to strengthen metals. But it simultaneously increases the electron scattering at the interface, thus reducing the electrical conductivity. In this study, we demonstrate that pure aluminum (Al)/carbon nanotubes (CNTs) nanocomposites prepared by friction stir processing have successfully broken through these limitations. The yield strength and tensile strength of Al/CNTs nanocomposites have improved by 104.7% and 51.8% compared to pure Al, while the electrical conductivity remained comparable to that of pure Al. To explore the potential mechanisms, the interface between CNTs and Al was examined and characterized by transmission electron microscopy (TEM) and Raman spectroscopy. Little interfacial reaction compounds were present and no visible physical gaps were observed at CNTs and Al interfaces. We defined it as a clean and tightly bonded interface. Although the quantity of phase interface has increased, the electrical conductivity of the nanocomposite remains approximately unchanged. We attribute the preserved electrical conductivity to the clean and tightly bonded CNTs/Al interface in the nanocomposite.

CsPbBr3 films have attractive applications in resistive switching memory, light-emitting diodes, photodetectors, and especially in perovskite solar cells (PSCs) because of their high stability and ease of fabrication under open air conditions. However, toxic solvents are usually employed to prepare CsPbBr3 films in these devices and pose potential threats to the health of manufacturers and the environment. Here, we develop a novel approach to achieve environment-friendly production of high quality CsPbBr3 films using water-soluble precursors of Pb(NO3)2 and CsBr in combination with phenethylammonium bromide (PEABr). In this approach, only green solvents of water and 2-propanol (IPA) are used to prepare CsPbBr3 films. After integrating into a solar cell with a typical configuration of FTO/TiO2/CsPbBr3/carbon, the best solar cell exhibits a power conversion efficiency (PCE) of 6.25% and has excellent stability in open air. This work not only provides a new approach to prepare high quality CsPbBr3 films, but also addresses the solvent toxicity during the fabrication of CsPbBr3 films, which makes it have extensive applications toward environment-friendly production of various CsPbBr3-based optoelectronic devices.

Toxic solvents used in the fabrication of perovskite films are a non-ignorable obstacle for the commercialization of perovskite solar cells (PSCs). CsPbBr3 based solar cells have attracted increasing attention due to their high stability in ambient air. Usually, a traditional sequential deposition route is employed to fabricate CsPbBr3 films, in which toxic DMF and methanol are separately used to dissolve PbBr2 and CsBr. In order to eliminate the solvent toxicity during the fabrication of CsPbBr3 films, we develop an anomalous sequential deposition route to prepare CsPbBr3 films. In this new route, a green solvent system composed of water with the addition of appropriate ethanol and ethylene glycol (EG) is developed to prepare the CsBr solution, and a green solvent, triethyl phosphate (TEP), is used to prepare the PbBr2 solution. Different from those obtained by the traditional sequential deposition route, CsBr films are firstly prepared from their solution, then reacted with PbBr2 through a dynamic spin-coating process, and subsequently transformed to CsPbBr3 films via annealing treatment. As a result, solar cells based on the device configuration of FTO/TiO2/CsPbBr3/carbon exhibit a power conversion efficiency of 6.86%, which is comparable to that of the PSCs prepared through the traditional sequential deposition route using toxic solvents. This work provides an environment-friendly route to prepare CsPbBr3 perovskite solar cells without efficiency loss.

All-carbon nanotube (CNT) hybrid films are fabricated through a facile vacuum filtration method by using hydrophilic single-walled carbon nanotube (SWCNT) films as filters and multi-walled carbon nanotube (MWCNT) powder dispersed in ethanol as liquor. The hydrophilic SWCNT film provides penetration channels for water, while the superhydrophobic MWCNTs have self-cleaning, self-spreading, and broadband absorption ability. The hybrid film exhibits ultra-high solar absorbance (∼99%), low thermal conductivity, and excellent light-to-heat conversion capacity. The temperature of the hybrid film increases from 24 to 60 °C in 1 s under one-sun illumination in air. The individual hybrid film exhibits a high water evaporation rate of 1.37 kg m−2 h−1 and a solar thermal efficiency of 87.4% under one-sun after 1 h illumination. The solar thermal efficiency maintains at ∼80% when many pieces of hybrid films self-assemble into a large film (∼40 cm2). The hybrid films have great potential in the desalination of seawater and sewage treatment. Ion concentrations in seawater decrease significantly to drinkable water standards by only one distillation treatment. Organic pollutants, such as rhodamine B and methylene blue, are removed effectively from sewage water by using the hybrid films in a solar steam generator.

Photothermoelectric materials have important applications in many fields. Here, we joined a silver nanostructure film (AgNSF) and a carbon nanotube film (CNTF) by van der Waals force to form a AgNSF/CNTF heterojunction, which shows excellent photothermal and photoelectric conversion properties. The local temperature difference and the output photovoltage increase rapidly when the heterojunction is irradiated by lasers with wavelengths ranging from ultraviolet to terahertz. The maximum of the local temperature difference reaches 205.9 K, which is significantly higher than that of other photothermoelectric materials reported in literatures. The photothermal and photoelectric responsivity depend on the wavelength of lasers, which are 175-601 K/W and 9.35-40.4 mV/W, respectively. We demonstrate that light absorption of the carbon nanotube is enhanced by local surface plasmons, and the output photovoltage is dominated by Seebeck effect. The AgNSF/CNTF heterostructure can be used as high-efficiency sensitive photothermal materials or as ultra-wideband fast-response photoelectric material., 11 figures

The crystallization of the perovskite structure of organic and inorganic halide depends on its composition and environmental condition. The most convenient method for the preparation of MAPbI3 pero...

Water has been labeled as a devil in fabrication and stability of perovskite solar cells. The inherent cognition impels researchers to prepare perovskite films in water-controlled conditions. Herein, water is used as a green solvent to prepare CsPbBr3 films through a two-step spin-coating method. Due to the high solubility of CsBr but low solubility of PbBr2 in water, it provides a possibility to deposit CsBr onto PbBr2 from water solution without destroying the film. Here, high-quality CsPbBr3 films are fabricated by spin-coating concentrated CsBr/H2O solution onto the PbBr2 film followed by annealing. As a result, the solar cells basing on a configuration of FTO/TiO2/CsPbBr3/Carbon exhibit a power conversion efficiency of 6.12%. This work provides a simple and easy way to prepare high-quality CsPbBr3 films for efficient solar cells. It makes a solid step toward reducing the solvent toxicity in the fabrication process of perovskite solar cells. It also breaks the forbidden zone for fabricating perovskite films from water and updates the inherent understanding of water in the research study of perovskite solar cells.

As an inevitable optoelectronic material with unique properties, halide perovskites have attracted increasing attention in recent years. Meanwhile, the hybridization of nanostructured perovskites w...

Cu(In, Ga)Se2 (CIGS) solar cells were fabricated by selenizing Cu-In-Ga precursors obtained by sputtering a Cu-In-Ga ternary alloy target. A preheating process was introduced during the selenization process to optimize the interface between the absorption layer and the buffer layer to improve the device performance. The results showed that the quality of the CIGS/CdS interface changed significantly with different preheating temperatures. A smoother interface indicated better p-n junction performance because of a more uniform distribution and better coverage of the buffer layer and intrinsic ZnO, as well as less interface recombination. Furthermore, there is less residue of Cu–Se compounds as the preheating temperature increases. Finally, the highest device efficiency of 14.35% was achieved at a preheating temperature of 300 °C.

Copper Indium Gallium Selenide (Cu(In,Ga)Se 2 , CIGSe) absorbers with different Ga contents were prepared by sputtering CIGSe ceramic targets and post-annealing. CIGSe solar cell devices were fabricated with other functional layers. The device performances and absorber properties were investigated. Increasing Ga content led to an increase in V OC and a decrease in J SC . Ga was supposed to diffuse towards back contact during the annealing process. The best performance was obtained as the ratio of Ga/(In + Ga) reaches 0.32 with the efficiency of 13.8% and a V OC of 537 mV.

Carbon nanotubes reinforced aluminum matrix nanocomposites were fabricated by friction stir processing. Raman spectroscopy, scanning electron microscope, transmission electron microscopy and tensile tests were used to characterize microstructures and mechanical properties of the nanocomposites. Effects of energy input during friction stir processing on microstructures and mechanical properties of the nanocomposites were investigated. It was found that the grain of aluminum matrix in the nanocomposites was coarsened slightly with the increase of energy input. Microstructure analysis showed that carbon nanotubes were successfully incorporated into aluminum matrix by friction stir processing and well bonded interfaces between the carbon nanotubes and aluminum matrix were formed. However, the carbon nanotubes dispersion and mechanical properties of the nanocomposites fabricated with different energy inputs were quite different, in which better carbon nanotubes dispersion and higher tensile strength could be obtained by applying higher energy input during the fabrication process. By applying the highest energy input, the tensile strength of the nanocomposite was 53.8% higher than that of the unreinforced aluminum. Meanwhile, the elongation of the nanocomposite was 31.2%, which showed an excellent ductility. The strengthening mechanisms were the synergy of Orowan looping, load transfer and grain refining. The present findings may provide the guidance on the optimization of the processing parameters during friction stir processing for fabricating the high performance aluminum/CNTs nanocomposites.

The sequential processes of sputtering quaternary CIGSe ceramic targets and annealing in sulfur-containing atmosphere were applied to prepare Cu(In,Ga)(Se,S)2 (CIGSeS) absorbers. Solar cell devices were fabricated with CIGSeS absorbers annealed in H2S-containing atmosphere with different H2S concentrations. Composition and microstructure of absorbers and performances of cells were investigated. Gallium tends to diffuse towards CIGSeS absorber surface as H2S concentration increases, furthermore leading to a Ga-rich layer at the surface. The Ga gradient and the incorporation of S at surface result in the enlarged band gap (Eg) in the space charge region (SCR). In this work, the conversion efficiency of CIGSeS solar cells could be promoted with the highest efficiency of 13.3%, with a VOC of 566 mV. The increasing Eg gradient towards surface enhances the suppress of deep level recombination, and the best device performance was achieved with the improvement of band gap structure as the annealing H2S concentration reached 15 vol%.

Carbon nanotube (CNT) films are promising materials for application in ultra-broadband photodetectors because their absorption range covers the entire spectrum from ultraviolet to the terahertz region, and their detection mechanism is the bolometric effect. Because of the different and limited photothermal conversion efficiencies of CNTs with respect to various wavelengths, the response performance of existing photodetector devices is unsatisfactory, particularly in the infrared band. In this paper, we propose for the first time the use of cesium tungsten bronze (Cs

Vanadium dioxide (VO2) is a strongly correlated electronic material and has attracted significant attention due to its metal-to-insulator transition and diverse smart applications. Traditional synthesis of VO2 usually requires minutes or hours of global heating and low oxygen partial pressure to achieve thermodynamic control of the valence state. Further patterning of VO2 through a series of lithography and etching processes may inevitably change its surface valence, which poses a great challenge for the assembly of micro- and nanoscale VO2-based heterojunction devices. Herein, we report an ultrafast method to simultaneously synthesize and pattern VO2 on the time scale of seconds under ambient conditions through laser direct writing on a V5S8 "canvas". The successful ambient synthesis of VO2 is attributed to the ultrafast local heating and cooling process, resulting in controlled freezing of the intermediate oxidation phase during the relatively long kinetic reaction. A Mott memristor based on a V5S8-VO2-V5S8 lateral heterostructure can be fabricated and integrated with a MoS2 channel, delivering a transistor with abrupt switching transfer characteristics. The other device with a VSxOy channel exhibits a large negative temperature coefficient of approximately 4.5%/K, which is highly desirable for microbolometers. The proposed approach enables fast and efficient integration of VO2-based heterojunction devices and is applicable to other intriguing intermediate phases of oxides.

Perovskite structures of organic and inorganic halides are peculiar structures with many interesting properties. Using their photoelectric effect, the structures have been used in photocells, photoelectric sensors, and light-emitting diodes. In conventional perovskite film crystallization, which is a one-step method, the MAPbI3 crystals form disordered needlelike crystals at room temperature. Such needlelike crystal films have rough surfaces and low coverage to the substrate, resulting in insignificant photoelectric effects. With the assistance of an electric field and three-dimensional (3D) printing, the direction of the perovskite needlelike crystal can be arranged to make it orderly. In this way, the photoelectric sensor of the ordered MAPbI3 perovskite needlelike crystal film can be prepared. This sensor has high sensitivity, high stability, and high response speed. Moreover, it has anisotropy and higher photoelectric sensitivity in the direction perpendicular to the needle crystal. Most interestingly, the sensors respond differently to polarized light in different directions, and this effect can be used to detect the direction and degree of polarization of polarized light.

High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone (NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH3NH3PbI3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

Recently, perovskite solar cells have attracted great attention because of their outstanding photovoltaic performance and ease of fabrication. High-quality perovskite films hold a key in getting highly efficient perovskite solar cells. Solution-processed fabrication technique is the most widely adopted for preparing perovskite films because of its low cost. In the solution-proceed perovskite films, solvents not only play the role of dissolving the solute but also participate in the crystallization of perovskite. In the one-step method, solvents play key roles in controlling morphology, widening process window, and achieving room-temperature crystallization of perovskite films. In addition, the solvents play important roles in controlling the nuclei/growth, suppressing volume expansion during the two-step method. Especially, the solvent can induce grain coarsening during the annealing process. A deep understanding of the multiplicity of roles during the formation of perovskite films will help understand the formation mechanism of perovskite films. Here, a systematic review on the progress in fabrication of high-quality perovskite films by making use of solvent to control the crystallization is presented. Meanwhile, we elucidate the key roles of solvent in the fabrication of high-quality perovskite films.

The low open circuit voltage (Voc) of Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells limits their efficiency. CZTSSe absorbers were fabricated by sputtering Cu2ZnSnS4 (CZTS) target and subsequent selenization treatment and then incorporated into solar cells. The influence of selenization temperature on the growth of the CZTSSe grains and device performance was examined. The absorber films were composed of a CZTSSe phase with high Se/(Se+S) ratios. As the selenization temperature was increased from 460 °C to 500 °C, the grains grew from the top to the bottom of the CZTSSe absorbers, and the average Voc of the CZTSSe solar cells increased from 284 mV to 371 mV. The band gaps (Eg), derived from external quantum efficiency (EQE) data, were approximately 1.11 eV. Activation energies (Ea) was extracted from temperature-dependent current density-voltage (J-V) measurements and used to evaluate the interface recombination level. The Ea increased from 0.82 eV to 0.89 eV as the selenization temperature was increased, which approached the Eg of CZTSSe. This was likely caused by reduced interface recombination because the grain boundaries decreased as the grains grew larger. An approximately linear relationship between the grain size and Voc was observed. The increase of grain size was achieved by optimizing the selenization temperature, which reduced interface recombination and resulted in an increased Voc. CZTSSe solar cells were fabricated with a maximum efficiency of 8.97%.

High-quality perovskite films with large grains and long carrier lifetime are crucial for efficient solar cells. It is a simple and effective way to increase the perovskite grain size by adding some additives in the precursor solution. Here, we use a low-toxicity and low-volatility organic compound of 1-ethyl-2-pyrrolidone (NEP) as an additive in the PbI2(PbBr2)/dimethylformamide precursor solution to form a Lewis adduct of PbI2·NEP, which facilitate forming perovskite intermediate embedded with NEP molecules. The residual NEP molecules are kept in the narrow space between the intermediate film and substrate during annealing by using a closed-steam annealing method, which prolong the dissolution-recrystallization process. With assistance of the residual NEP, high-quality perovskite films with smooth surface, PbI2 free, high crystallinity, large columnar grains, and long carrier lifetime are fabricated. Correspondingly, the power conversion efficiency of the best perovskite solar cells is enhanced signific...

Perovskite films are usually fabricated by a solution-processed method due to its low cost and ease of fabrication. The organic solvent plays multiple roles in the growth of perovskites. Here, we i...

Fabrication of wide band-gap (Eg) CuGaSe2 (CGSe) thin film solar cells with large area uniformity and good reproducibility is difficult, which is crucial for tandem cells. In this work, a method was proposed and investigated to overcome this problem. CGSe solar cells were fabricated by sputtering from a ternary CGSe target and post selenization treatment at different temperatures. After selenization, the CGSe grains grow up gradually, and the copper-poor and selenium-rich CGSe absorbers are obtained successfully. The X-ray diffraction peaks are all corresponded to CGSe phase. As the temperature increases from 530 to 570 °C, the average efficiency increases from 1.57% to 3.11%. When the temperature reaches 590 °C, the efficiency drops to 2.38%. The champion device obtained at 570 °C shows an Eg of 1.66 eV and an efficiency of 3.21%, which indicates the potential for the top cell in tandem solar cells.

Superhydrophobic surface has attracted enormous interests due to its attractive potential applications. Here, we prepare all carbon nanotube hybrid films simply by depositing multi-walled carbon nanotubes on strong single-walled carbon nanotube films through vacuum filtration. The hybrid films behave some exciting superhydrophobic properties of a large water contact angle of 152° and an ultra-low sliding angle of only 2°. The rebounding height of a water droplet dipping from 5 cm above the hybrid film reaches 9.4 mm, which is 3 times that of on the natural lotus leaf. The superhydrophobic hybrid film also have high specific loading capacity of 627 g/g, more than 12 times that of the natural lotus leaf. The hybrid films can mimic lotus leaf in water repelling, self-cleaning, and carrying heavy things quite well.

Ultra-broad spectral detection is critical for several technological applications in imaging, sensing, spectroscopy, and communication. Carbon nanotube (CNT) films are a promising material for ultra-broadband photodetectors because their absorption spectra cover the entire ultraviolet to the terahertz range. However, because of the high binding energy of excitons, photodetectors based on CNT films always require a strong electric field, asymmetric electrical contacts, or hybrid structures with other materials. Here, we report an ultra-broadband bolometric photodetector based on a suspended CNT film. With an abundant distribution of tube diameters and an appropriate morphology (spider web-like), the CNT films display a strong absorption spectrum from the ultraviolet up to the terahertz region. Under illumination, heat generated from the electron-photon interaction dominates the photoresponse of our devices. For small changes in temperature, the photocurrent shows a convincing linear dependence with the absorbed light's power across 3 orders of magnitude. When the channel length is reduced to 100 μm, the device demonstrates a high performance with an ultraviolet responsivity of up to 0.58 A/W with a bias voltage of 0.2 V and a short response time of ∼150 μs in vacuum, which is better than that of many other photodetectors based on CNTs. Moreover, this performance could be further enhanced by optimization.

Thermal annealing plays multiple roles in fabricating high quality perovskite films. Generally, it might result in large perovskite grains by elevating annealing temperature, but might also lead to decomposition of perovskite. Here, we study the effects of annealing temperature on the coarsening of perovskite grains in a temperature range from 100 to 250 °C, and find that the coarsening rate of the perovskite grain increase significantly with the annealing temperature. Compared with the perovskite films annealed at 100 °C, high quality perovskite films with large columnar grains are obtained by annealing perovskite precursor films at 250 °C for only 10 s. As a result, the power conversion efficiency of best solar cell increased from 12.35% to 16.35% due to its low recombination rate and high efficient charge transportation in solar cells.

Pure kesterite Cu2ZnSnSe4 (CZTSe) absorbers with a large average grain size are vital for high-efficiency CZTSe solar cells, which are greatly influenced by the annealing atmosphere. Sputtered CZTSe precursors were annealed in the presence and absence of a selenium-containing atmosphere, and these materials were incorporated into solar cells. When annealed in an Ar atmosphere, the CZTSe absorbers were found to be composed of small grains with the presence of voids and secondary phases. When H2Se was added into the chamber at a temperature of 550 °C, the CZTSe grains increased in size and the presence of the voids and secondary phases reduced. When H2Se was added at a lower temperature (300 °C) earlier in the annealing process, the average grain size increased further and device efficiencies were higher. When H2Se was continuously added into the chamber during the whole selenization process, the average grain size increased to approximately 2 μm, the undesired secondary phases were not detected and the efficiency of the CZTSe devices reached a maximum of 6.78%. This work showed that exposing the CZTSe precursors to a selenium atmosphere during annealing increased the average grain size and reduced the presence of undesirable secondary phases, thus improving the performance of CZTSe absorbers and solar cells.

Compositional engineering of mixed halides is an effective approach to fabricate highly efficient perovskite solar cell. The mixed halide perovskite of MAPbI3-xClx attracts a great of attentions due to its excellent optoelectronic properties. However, the role of chlorine in MAPbI3-xClx is still under discussion by now. Here we introduce PbCl2 as additives into PbI2/DMF solution to study its effects on the formation of MAPbI3-xClx film, which is fabricated from Lewis acid-base adducts through a modified two step method. We demonstrate that the chloride ions have positive roles in fabrication of high quality perovskite MAPbI3-xClx films, characterized by high crystallization, strong grain orientation, large grain size and lower trap densities. Compared to perovskite solar cells without chloride incorporation, the performance of solar cells based on MAPbI3-xClx improves significantly due to its high carrier mobility, efficient carrier transportation and low recombination in device.

The properties of organic–inorganic hybrid perovskites greatly depend on their compositions. Here, we investigate the crystallization of methylammonium lead mixed halide (MAPbI3–xBrx) from microdroplets by adjusting the molar ratio of iodine to bromine in precursor solution, which helps to control the morphology, crystallinity, and physical properties of the perovskite materials. The composition of the precursor solutions has profound effects on the crystallization and perovskite morphology. It tends to form needle intermediate crystals of MAPbI3−xBrx·DMF from the precursor solution at low bromine concentration, while it tends to form flake or cubic perovskite of MAPbI3−xBrx at high bromine concentration. There is evident composition segregation of bromine when the perovskite and its intermediate grow freely from the solution at low temperature. At a high growing temperature of 100 °C, continuous perovskite films consisting of large crystal domains with sizes up to 100 μm are fabricated from the precursor...

Generally, residual solvent is embedded in perovskite precursor films fabricated from the Lewis adduct method. Most of the research focus on the ligand function of the solvent in forming a solvate complex for fabricating high quality perovskite films. However, little attention has been paid to the latent function of the solvent in the perovskite precursor films during the annealing process due to its fast extravasation at high temperature. Here, we develop a sandwich configuration of substrate/perovskite precursor films/PC61BM to retard the extravasation of solvent during annealing. We find that the restrained solvent induces an obvious solvent-mediated dissolution–recrystallization process, leading to high quality perovskite films with large columnar grains. There is mass transportation from small grains to large grains in the dissolution–recrystallization process, which follows the Ostwald ripening model. Inverted planar solar cells are fabricated on the basis of this annealing method. The photovoltaic ...

The physical properties of organic–inorganic hybrid perovskite materials are greatly influenced by their composition, crystallinity, and morphology. Here, we investigate the growth of CH3NH3PbI3−xBrx perovskite from micro-droplets of a methylammonium iodide/lead acetate/dimethylformamide precursor solution added with different concentrations of PbBr2, which helps to control the morphology and crystallinity of the perovskite film. We find that both perovskite and its intermediate containing an acetate group growing from the micro-droplets. By adding some PbBr2, there is a tendency to form cubic perovskite crystals due to partial substitution of iodine with bromide. There is composition segregation when the crystals grow freely from the droplets. Smooth and uniform CH3NH3PbI3−xBrx perovskite films with a tunable band gap are thus fabricated from the precursor solution added with PbBr2.

The transient liquid phase diffusion bonding (TLPB) method was used to repair an artificial crack in Inconel 738, which was notched by a femtosecond laser. Mixed ratios of BNi-1a:DF-4B were investigated at the bonding temperature of 1373 K (1100 °C) for 2 to 36 hours. The effect of borides on the mechanical properties of TLPB repaired joints was studied through analysis of the microstructure, fracture path, and morphology observations. The borides formation, morphology, distribution, and joints strength were studied in detail. The results showed that the diffusion of B can either increase or decrease the joint strength, depending on its distribution and morphology. The amount of large blocky Ni-B compounds in the precipitate zone were reduced with increasing holding time, which resulted in an increase in joint strength. Nevertheless, further increasing the holding time led to a decrease in joint strength because of the formation of continuous acicular borides in the diffusion-affected zone. The fracture modes of TLPB joints were also discussed on the basis of the microstructure and fractography.

The CdS layers are vital for diode quality of cell devices, which have great influences on high-performance CZTSSe solar cells. Optimizing the deposition processes of CdS layers are necessary to improve the diode quality and device efficiency. In this work, CZTSSe solar cells were fabricated without and with pre-deposited CdS layers, which are referred to as one-step and two-step processes, respectively. Then the performances of the CZTSSe solar cells were comparatively studied. Comparing with one-step processes, the efficiency of the solar cell by two-step processes improves from 7.24% to 9.45%. The efficiency improvement is mainly due to the gain of fill factor (FF) from 60.3% to 73.1%. Although the cell devices by different CdS processes have similar levels of interface recombination deduced from the activation energy (Ea), the temperature-dependent ideality factor A and shunt resistance (Rsh) indicate that the device fabricated by two-step possess higher diode quality and lower leakage current, which results in the increase of FF and efficiency. The optimization of CdS layer preparation is an effective approach to improve the efficiencies of solar cells.

Water has been labeled as a devil in fabrication and stability of perovskite solar cells. The inherent cognition impels researchers to prepare perovskite films in water-controlled conditions. Herein, water is used as a green solvent to prepare CsPbBr