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Although perovskite solar cells have achieved great breakthroughs in photoelectric conversion efficiency (PCE), some challenges still need to be addressed before commercialization. Lead leakage is harmful to the environment and many methods are developed to prevent lead leakage; among them, chemical adsorption has proved to be an effective way. Herein, a simple and low‐cost strategy that can enhance the device performance and mitigate the lead leakage by applying l‐phenylalanine in the interface of NiOx/perovskite is reported. The results show that this strategy can improve the morphology and conductivity of the NiOx film, optimize the NiOx/perovskite interface energy level, resulting in an efficient and stable device with a PCE of 19.0%. Furthermore, the interface modification improves the stability of the perovskite film through strong interaction with the perovskite, inhibits the decomposition of the film in water, slows down the process of lead leakage, and protects the environment from lead pollution. The devices maintain 86% initial efficiency for 200 h maximum power point measurement and 94% for 2100 h under nitrogen. [ABSTRACT FROM AUTHOR]

Over the past few years, all‐inorganic perovskite solar cells (PSCs), especially CsPbI2Br PSCs, have received much attention because of their excellent thermal stability and a suitable trade‐off between light absorption and higher phase stability among the family of inorganic perovskites. In this progress report, the realization of highly efficient and stable CsPbI2Br PSCs is summarized through preparation process, additive engineering, interface modification, and transport material selection. Furthermore, the application of CsPbI2Br in tandem solar cells and its large‐area development are highlighted. Finally, the challenges and outlook of CsPbI2Br PSCs are discussed for further performance improvement and future practical deployment. [ABSTRACT FROM AUTHOR]

The quality of the perovskite film is crucial to the technological breakthrough of perovskite solar cells (PSCs). The two‐step method can facilitate the formation of a perovskite film with high quality and reproducibility. Many milestones have been made in the development of hybrid lead halide PSCs by using the two‐step method, which has a significant impact on their practical application. Herein, the reaction mechanism of the two‐step method including two‐step immersion method and two‐step spin coating method is summarized. The strategies such as component engineering, solvent engineering, and additive engineering of the two‐step method in preparing high‐quality films are introduced systematically and in detail. In addition, current issues of the two‐step method and its applications in lead‐free PSCs, all‐inorganic PSCs, large areas, and tandems are introduced and some suggestions are put forward for future research. [ABSTRACT FROM AUTHOR]

All‐inorganic perovskites have attracted substantial interest due to their outstanding thermal stability. However, the device performance is still inferior to the typical organic–inorganic counterparts because of the unsatisfying phase stability and defects of the inorganic perovskite films. Herein, a multistrategy to optimize CsPbI2Br perovskite solar cells (PSCs) based on dopant‐free poly(3‐hexylthiophene) (P3HT) by applying thienylmethylamine acetate additive to enhance the α phase stability and passivate the bulk defects of CsPbI2Br perovskite is successfully demonstrated, followed by implementing BTCIC‐4Cl interlayer at CsPbI2Br/P3HT interface, which can coordinate with both perovskite and P3HT to suppress the surface defects and promote the hole transport. Benefitting from these, a champion power conversion efficiency (PCE) of 16.3% is achieved, and the unencapsulated optimized device can retain 97% of the initial PCE after aging under N2 atmosphere at 85 °C for 530 h. This work opens up a new era of multistrategy for improving performance and stability of CsPbI2Br PSCs based on dopant‐free hole transport layer. [ABSTRACT FROM AUTHOR]

Organic–inorganic lead halide perovskite solar cells (PSCs) have demonstrated enormous potential as a new generation of solar‐based renewable energy. Although their power conversion efficiency (PCE) has been boosted to a spectacular record value, the long‐term stability of efficient PSCs is still the dominating concern that hinders their commercialization. Notably, interface engineering has been identified as a valid strategy with extraordinary achievements for enhancing both efficiency and stability of PSCs. Herein, the latest research advances of interface engineering for various interfaces are summarized, and the basic theory and multifaceted roles of interface engineering for optimizing device properties are analyzed. As a highlight, the authors provide their insights on the deposition strategy of interlayers, application of first‐principle calculation, and challenges and solutions of interface engineering for PSCs with high efficiency and stability toward future commercialization. [ABSTRACT FROM AUTHOR]

Longevity is a long‐standing concern for organic–inorganic hybrid perovskite solar cells (PSCs). Recently, the use of low dimensional perovskite has been proven to be a promising strategy to improve the stability of PSCs. Herein, it is demonstrated that 1D perovskitoid based on 2‐diethylaminoethylchloride cations can act as a template to induce 1D@3D perovskite structure, leading to smoother surface texture, longer charge‐carrier lifetime, smaller residual tensile strain, and reduced surface‐defect density in the perovskite film. With this strategy, highly efficient and stable 1D@3D PSC with excellent reproducibility, showing a champion power conversion efficiency (PCE) of 22.9% under standard AM 1.5 G one sun illumination is realized. The unencapsulated optimized devices can retain 94.7%, 92.4%, and 90.0% of their initial PCEs for 2100, 2200, and 2200 h under ambient air, 85 °C and illumination conditions, respectively. [ABSTRACT FROM AUTHOR]

Capacitive response at long time scales seems to remain an elusive feature in the analysis of the electrical properties of perovskite‐based solar cells. It belongs to one of the critical anomalous effects that arises from the characteristic phenomenology of this type of emerging photovoltaic devices. Thereby, accurately deducing key capacitance feature of new light harvesting perovskites from electrical measurements represents a significant challenge regarding the interpretation of physical processes and the control of undesired mechanisms, such as slow dynamic effects and/or current density–voltage (J–V) hysteresis. Herein, it is shown that long timescale mechanisms that give rise to hysteresis in stable and high‐efficiency quadruple‐cation perovskites are not due to a classical capacitive behavior in the sense of ideal charge accumulation processes. Instead, it is a phenomenological consequence of slow memory‐based capacitive currents and the underlying cooperative relaxations. A fractional dynamics approach, based on the idea of capacitance distribution in perovskite devices, reliably models the slow transient phenomena and the consequent scan‐rate‐ and bias‐dependent hysteresis. Observable for a wide variety of photovoltaic halide perovskites, distributed capacitive effects are rather universal anomalous phenomena, which can be related to the long‐time electrical response and hysteresis. [ABSTRACT FROM AUTHOR]

Comparisons between different laboratories on long‐term stability analyses of perovskite solar cells (PSCs) is still lacking in the literature. This work presents the results of an interlaboratory study conducted between five laboratories from four countries. Carbon‐based PSCs are prepared by screen printing, encapsulated, and sent to different laboratories across Europe to assess their stability by the application of three ISOS aging protocols: (a) in the dark (ISOS‐D), (b) under simulated sunlight (ISOS‐L), and (c) outdoors (ISOS‐O). Over 1000 h stability is reported for devices in the dark, both at room temperature and at 65 °C. Under continuous illumination at open circuit, cells survive only for few hours, although they recover after being stored in the dark. Better stability is observed for cells biased at maximum power point under illumination. Finally, devices operate in outdoors for 30 days, with minor degradation, in two different locations (Barcelona, Spain and Paola, Malta). The findings demonstrate that open‐circuit conditions are too severe for stability assessment and that the diurnal variation of the photovoltaic parameters reveals performance to be strongly limited by the fill factor, in the central hours of the day, due to the high series resistance of the carbon electrode. [ABSTRACT FROM AUTHOR]

In the last decade, lead triiodide perovskite (APbI3) (A: organic cation) solar cells (PSCs) have been broadly studied due to their promising features related to the low cost, easy manufacturing process, and stability. Strategies to improve the device stability include the application of techniques such as compositional engineering of the cation of these halide perovskites, but it is still a complex task to find the right balance between the stability and power conversion efficiency of materials and complete devices. In this work, we performed a combined study of five samples of [5-AVA(1−x)MAx]PbI3 (5-AVA: ammonium valeric acid and MA: methylammonium) with x = 1.0, 0.75, 0.5, 0.25 and 0.0, using X-ray diffraction (XRD) and UV-VIS spectroscopy measurements in combination with periodic density functional theory (DFT) based calculations. Our samples showed an optical bandgap of 1.58 eV and the coexistence of the two phases as observed by XRD analyses. The theoretical results of the bandgaps for the no mixed phases (x = 1.0 and x = 0.0) show good agreement with the experiment, obtaining bandgap values overestimated by 0.18 eV and 0.33 eV, respectively. A direct relation between the number of 5-AVA ions in the samples and the stability of the phases was theoretically found and proved through the increment observed in the bandgap and the cohesive energy. We proposed a compositional strategy for perovskites [5-AVA(1−x)MAx]PbI3 with x values of at most 0.5, based on the small blue-shift and the low absorbance reduction of the spectrum curve, added to the small phase stabilization found. [ABSTRACT FROM AUTHOR]

The orthotropic membrane structures have been popular in architectural structures. However, because of its lightweight and small stiffness, large nonlinear deflection vibration may occur under impact load, which leads to structural failure. In this paper, the governing equations of the large deflection nonlinear damped vibration of orthotropic saddle membrane structures excited by hailstone impact load are proposed according to the von Kármán's large deflection theory and solved by applying the Bubnov–Galerkin method and the method of KBM perturbation. The approximate theoretical solution of the frequency function and displacement function of the large deflection nonlinear damped vibration of saddle membrane structures with four edges fixed excited by hailstone impact was obtained. The analytical examples proved that the mode shape function (equation (43)) can be applied to calculate the single-order mode shapes and the total superposed mode shapes of the damped large nonlinear deflection vibration of orthotropic saddle membrane structures excited by hailstone impact load succinctly. In addition, we compare and analyze the results of vibration frequency, amplitude, time histories, and total displacement of membrane structures with different pretensions and arch-to-span ratios under the impact of differently sized hailstones. The correctness of the analytical theory is verified by comparing with the results of numerical simulation. According to the results of this paper, we put forward some suggestions for the vibration control and dynamic design of practical spatial membrane structures. [ABSTRACT FROM AUTHOR]

Microstructural properties of Cu2ZnSn(SxSe1−x)4 kesterite solid solutions were investigated using grazing incidence X-ray diffraction for the full interval of anion compositions in order to explore the influence of S and Se atoms on the thin film morphology. Thin films were prepared by sputtering deposition of metallic precursors, which were then submitted to a high temperature sulfo-selenization process. By adjusting process parameters samples from sulfur- to selenium-pure (0 ≤x≤ 1) were made. Microstructural analysis shows a strong dependence of domain size and microstrain on composition. Both values increase with higher sulfur content, and depth profile analysis by grazing incidence X-ray diffraction shows selenium-rich films tend to have a more homogeneous depth distribution of domain size. The increasing trend in domain size of S-rich absorbers can be related to lower formation energies of the sulfur binary phases leading to formation of kesterites, while the increase in the microstrain is explained by the substitution of larger Se atoms with smaller S atoms in the host lattice and the presence of secondary phases. [ABSTRACT FROM AUTHOR]

In this work we report on the effect of alkali doping via Na and/or K introduction into flexible and light-weight Cu2ZnSnSe4 (CZTSe) solar cells obtained using a sequential process based on the sputtering of metallic stacks and further reactive annealing. Different thicknesses of Cr diffusion barriers and 50 μm thick ferritic steel substrates were used. We compare different doping methods: Na-doped Mo targets (MoNa), SLG underneath the flexible substrates, NaF and KF pre-absorber synthesis evaporation (PAS) and post-deposition evaporation (PDT). Additionally, we report on the importance of the Cr barrier and back contact modification to improve solar cell performance. A remarkable enhancement in the absorber grain size and surface morphology occurred especially when using Na via MoNa and PAS. Nevertheless, preliminary experiments led to better results for MoNa doping due to a higher Na content confirmed by TOF-SIMS. K doping via PAS also showed promising results. An increase in the efficiency of solar cells from 2.2% to 4.3% was possible when using a MoNa layer sandwiched between regular Mo layers. The improvement is mainly related to a higher VOC and FF. After performing a detailed Cr and back contact optimization, a record value of 6.1% for flexible CZTSe solar cells was recently obtained using MoNa and a new surface Ge doping. [ABSTRACT FROM AUTHOR]

A large improvement in Cu2ZnSnSe4 solar cell efficiency is presented based on the introduction of a Ge superficial nanolayer. This improvement is explained by three complementary effects: the formation of a liquid Ge‐related phase, the possible reduction of Sn multicharge states, and the formation of GeOx nanoinclusions, which lead to an impressive solar cell (VOC) increase. [ABSTRACT FROM AUTHOR]

A spike-like conduction band alignment of kesterite absorbers with a CdS buffer layer is one of the key factors for high-performance solar cells using this buffer/absorber heterojunction combination. However, it can also be the origin of fill factor and current-reducing distortions in current-voltage curves, such as light/dark curve crossover, or an s-like curve shape for long wavelength monochromatic illumination (red kink) if light-dependent defect states are present in the buffer layer. In this work, we show that by changing the cadmium precursor source from sulfate to nitrate salts for the chemical bath deposited cadmium sulfide for Cu2ZnSnSnSe4/CdS heterojunction solar cells red kink can be eliminated, and crossover greatly improved (and eliminated entirely after light soaking). These improvements lead to a decrease in series resistance and an increase in fill factor and increase power conversion efficiency from 7.0% to 8.2%. We attribute this improvement to a reduction of deep level acceptor-like traps states inside the CdS layer, which are responsible for an increase of the conduction band spike up to a current blocking value for the sulfate precursor case. Furthermore, the effects of light soaking will be discussed. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this work, Raman spectroscopy and X-ray diffraction were applied together to evaluate the crystal structure and the phonon modes of photovoltaic grade Cu2ZnSn(SxSe1-x)4 thin films, leading to a complete characterization of their structural and vibrational properties. Vibrational characterization has been based on Raman scattering measurements performed with different excitation wavelengths and polarization configurations. Analysis of the experimental spectra has permitted identification of 19 peaks, which positions are in good accord with theoretical predictions. Besides, the observation of Cu2ZnSnS4-like A symmetry peaks related to S vibrations and Cu2ZnSnSe4-like A symmetry peaks related to Se vibrations, additional Raman peaks, characteristic of the solid solution and previously not reported, are observed, and are attributed to vibrations involving both S and Se anions. [ABSTRACT FROM AUTHOR]

Perovskite Solar Cells In article number 2000707, Enrique Hernández‐Balaguera and co‐workers explored the inherent characteristic phenomenology of perovskite solar cells, in terms of anomalous ionic and electronic dynamics, long‐memory effects, and anomalous hysteresis, using electrical analysis strategies and fractional calculus tools. Thus, this work can help to advance in the understanding of the key attributes and unique physical mechanisms of photovoltaic perovskites at long time scales. [ABSTRACT FROM AUTHOR]

A strategy for interface engineering of hetero‐junctions in kesterite solar cells by using Al(OH)3 is demonstrated. The hydroxide nanolayers are prepared via a facile and fast wet chemical route, based on an aqueous solution of aluminum chlorides and thioacetamide. Considerable enhancement of open circuit voltage (Voc) (30–60 mV) and fill factor (FF) (10–20%) after this chemical treatment are observed, achieving a champion conversion efficiency of 9.1% and a champion FF of 70% (among the best FF in kesterite solar cells). The functional mechanism is systematically studied by current‐voltage, capacitance‐voltage, temperature dependence of current–voltage and photoluminescence measurements, which reveal that Al(OH)3 nanolayers can effectively reduce the interface recombination and largely improve the shunt resistance. Furthermore, atomic resolution high angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) evidences the epitaxial relationship of Al(OH)3 with kesterite and CdS, indicating the benign and effective interface passivation achieved by this chemical treatment. Finally, based on HAADF‐STEM and electron energy loss spectroscopy mappings, insights into the efficiency limiting and beneficial factors for CZTSSe solar cells, as well as suggestions to further improve both the bulk and related interfaces are presented. Al(OH)3 nanolayers are employed for the interface modification of Cu2ZnSn(S,Se)4/CdS hetero‐junction of kesterite solar cells. Considerable open circuit voltage and fill factor increment are observed, which is ascribed to reduced interface recombination and shunt paths by an epitaxial relationship of Al(OH)3 with kesterite and CdS. [ABSTRACT FROM AUTHOR]

Oxides employed in halide perovskite solar cells (PSCs) have already demonstrated to deliver enhanced stability, low cost, and the ease of fabrication required for the commercialization of the technology. The most stable PSCs configuration, the carbon‐based hole transport layer‐free PSC (HTL‐free PSC), has demonstrated a stability of more than one year of continuous operation partially due to the dual presence of insulating oxide scaffolds and conductive oxides. Despite these advances, the stability of PSCs is still a concern and a strong limiting factor for their industrial implementation. The engineering of oxide interfaces functionalized with molecules (like self‐assembly monolayers) or polymers results in the passivation of defects (traps), providing numerous advantages such as the elimination of hysteresis and the enhancement of solar cell efficiency. But most important is the beneficial effect of interfacial engineering on the lifetime and stability of PSCs. In this work, the authors provide a brief insight into the recent developments reported on the surface functionalization of oxide interfaces in PSCs with emphasis on the effect of device stability. This paper also discusses the different binding modes, their effect on defect passivation, band alignment or dipole formation, and how these parameters influence device lifetime. Metal oxides applied as transport layers in perovskite solar cells provide enhanced efficiency and improved performance in long timescales operating solar cells. Interfacial engineering of oxides can be made through organic molecules with different anchoring groups which passivate traps and reduce hysteresis. Oxides can also be employed as highly conductive electrodes when doped, or as oxide/oxide bilayers enhancing device lifetime. [ABSTRACT FROM AUTHOR]

In article number 1501070, Edgardo Saucedo and co‐workers report a breakthrough in kesterite‐based technologies, demonstrating that high‐voltage and high‐efficiency devices can be easily achieved using an innovative approach based on the introduction of a superficial Ge nanolayer, leading to efficiencies exceeding 10%. To illustrate this, the image shows how materials management at nanoscale level can have a strong impact on the macroscopic properties of photovoltaic devices. [ABSTRACT FROM AUTHOR]