Abstract
Even though the mesoporous-type perovskite solar cell (PSC) is known for high efficiency, its planar-type counterpart exhibits lower efficiency and hysteretic response. Herein, we report ...success in suppressing hysteresis and record efficiency for planar-type devices using EDTA-complexed tin oxide (SnO
2
) electron-transport layer. The Fermi level of EDTA-complexed SnO
2
is better matched with the conduction band of perovskite, leading to high open-circuit voltage. Its electron mobility is about three times larger than that of the SnO
2
. The record power conversion efficiency of planar-type PSCs with EDTA-complexed SnO
2
increases to 21.60% (certified at 21.52% by Newport) with negligible hysteresis. Meanwhile, the low-temperature processed EDTA-complexed SnO
2
enables 18.28% efficiency for a flexible device. Moreover, the unsealed PSCs with EDTA-complexed SnO
2
degrade only by 8% exposed in an ambient atmosphere after 2880 h, and only by 14% after 120 h under irradiation at 100 mW cm
−2
.
Fullerene derivative, such as 6,6-phenyl C61 butyric acid methyl ester (PCBM), is widely used as an electron-transport layer (ETL) in inverted perovskite solar cell (PSC). However, its low electron ...mobility, complexity in achieving quality film formation, and severe nonradiative recombination at perovskite/PCBM interface due to the large electron capture region, lead to lower efficiency for inverted PSCs compared to the normal structures. Herein, we demonstrate an effective and practical strategy to overcome these challenges. Conjugated n-type polymeric materials are mixed together with PCBM to form a homogeneous bulk-mixed (HBM) continuous film with high electron mobility and suitable energy level. HBM film is found to completely cap the perovskite surface to enhance the electron extraction. The critical electron capture radius of the HBM decreases to 12.52 nm from 14.89 nm of PCBM due to the large relative permittivity, resulting in reduced nonradiative recombination at perovskite/HBM interface. The efficiency of inverted PSCs with HBM ETLs exceeds 20.6% with a high fill factor of 0.82. Further, the stability of devices is improved owing to the high hydrophobicity of the HBM ETLs. Under ambient air condition after 45 days, the efficiency of inverted PSCs based on HBM remains 80% of the initial value. This is significantly higher than the control devices which retain only 48% of the initial value under similar aging conditions. We believe these breakthroughs in improving efficiency and stability of inverted PSCs will expedite their transition.
The solution processability of photoactive halide perovskites differentiates them from traditional inorganic semiconducting materials that require multiple post-processing steps such as ...thermal/vacuum/blowing- and solvent-assisted treatment. Here we report a technical breakthrough of isothermally crystallizing high-quality perovskite films at room-temperature (RT) without the necessity of any post-processing. This process takes advantage of our discovery of a metastable intermediate of lower-dimensionality formed by amine-assisted crystallographic lattice expansion from an initial three-dimensional perovskite. Using
in situ
optoelectrical/chemical and
ex situ
structural characterizations, a detailed understanding of the low-dimensional metastable intermediate is developed. In conjunction with the metastable intermediate, the rapid evaporation of the solvent and amine facilitates ultra-fast crystallization at RT within seconds. This RT rapidly synthesized perovskite film exhibits a carrier diffusion length of 2.9 μm and {00
} preferred orientation with an ultrahigh Lotgering factor of 97%. These films are highly compatible to conventional or inverted devices, demonstrating 22.3% and 23.1% power conversion efficiencies, respectively.
We have developed a paradigm methodology that can isothermally crystallize halide perovskites at room temperature.
Neurodegenerative diseases (ND) have received increasing attention due to their irreversibility, but there is still no means to completely cure ND in clinical practice. Mindfulness therapy (MT), ...including Qigong, Tai Chi, meditation, and yoga, etc., has become an effective complementary treatment modality in solving clinical and subclinical problems due to its advantages of low side effects, less pain, and easy acceptance by patients. MT is primarily used to treat mental and emotional disorders. In recent years, evidence has shown that MT has a certain therapeutic effect on ND with a potential molecular basis. In this review, we summarize the pathogenesis and risk factors of Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), relating to telomerase activity, epigenetics, stress, and the pro-inflammatory transcription factor nuclear factor kappa B (NF-κB) mediated inflammatory response, and analyze the molecular mechanism basis of MT to prevent and treat ND, to provide possible explanations for the potential of MT treatments for ND.
In the past five years, perovskite solar cells (PSCs) based on organometal halide perovskite have exhibited extraordinary photovoltaic (PV) performance. However, the PV measurements of PSCs have been ...widely recognized to depend on voltage scanning condition (hysteretic current density–voltage J–V behavior), as well as on voltage treatment history. In this study, we find that varied PSC responses are attributable to two causes. First, capacitive effect associated with electrode polarization provides a slow transient non-steady-state photocurrent that modifies the J–V response. Second, modification of interfacial barriers induced by ion migration can modulate charge-collection efficiency so that it causes a pseudo-steady-state photocurrent, which changes according to previous voltage conditioning. Both phenomena are strongly influenced by ions accumulating at outer interfaces, but their electrical and PV effects are different. The time scale for decay of capacitive current is on the order of seconds, whereas the slow redistribution of mobile ions requires several minutes.
Though formamidinium lead triiodide (FAPbI3) possesses a suitable band gap and good thermal stability, the phase transition from the pure black perovskite phase (α-phase) to the undesirable yellow ...nonperovskite polymorph (δ-phase) at room temperature, especially under humid air, hinders its practical application. Here, we investigate the intrinsic instability mechanism of the α-phase at ambient temperature and demonstrate the existence of an anisotropic strained lattice in the (111) plane that drives phase transformation into the δ-phase. Methylammonium bromide (MABr) alloying (or FAPbI3-MABr) was found to cause lattice contraction, thereby balancing the lattice strain. This led to dramatic improvement in the stability of α-FAPbI3. Solar cells fabricated using FAPbI3-MABr demonstrated significantly enhanced stability under the humid air.
Hemodialysis (HD) patients are more inactive, leading to poor functional capacity and quality of life; this may be reversed with intradialytic exercise training. To systematically evaluate the ...efficacy and safety of intradialytic exercise for HD patients, we conducted a meta-analysis of the published randomized controlled trials.
Medline, Embase, and Cochrane Central Register of Controlled Trials were systematically searched up to February, 2014. The reference lists of eligible studies and relevant reviews were also checked.
24 studies of 997 patients were included. Compared with control, intradialytic exercise significantly improve Kt/V (SMD = 0.27, 95% CI 0.01-0.53), peak oxygen consumption (VO(2peak)) (SMD = 0.53, 95% CI 0.30-0.76), and physical performance of physical function of life (SMD = 0.30, 95% CI 0.04-0.55). However, no significant improvements were found in the mental function of life. There was no significant difference with respect to musculoskeletal and cardiovascular complications between the intradialytic exercise groups and control groups. Further subgroup analysis found that, when the trial duration was more than 6 months, the intervention had significant effects on VO(2peak) (SMD = 0.89, 95% CI 0.56-1.22). However, when the trial duration was less than 6 months, the change of VO(2peak) was not significant (SMD = 0.19, 95% CI -0.13 to 0.51).
Intradialytic exercise can improve Kt/V, VO(2peak), and the physical quality of life, and intradialytic exercise is safe for HD patients. Therefore, we put forward the suggestion that clinical guideline be updated to inform clinicians on the benefits of intradialytic exercise on HD patients.
High-purity monocrystalline silicon has a long history in the development of photovoltaics; so far, it has dominant applications in modern computers with its profound implementations in transistors ...and chips. The success of silicon has shown that monocrystalline wafers/thin films of semiconducting materials with superior electronic properties are a good platform for optoelectronic and electronic applications. Recently, the newly emerging semiconducting materials of halide perovskites (HPs) have attracted considerable attention owing to their continuing success in high-efficiency solar cells. The demonstrated optoelectronic properties of HPs indicate that it could be a promising alternative to the silicon-based semiconducting industry. However, the prerequisite of high-efficiency devices is the material accessibility of monocrystalline HPs (mono-HPs), as per the lessons learned from monocrystalline silicon. Current HPs-based technologies, in terms of research areas such as solar cells, photodetectors, light-emitting diodes (LEDs), lasers, and transistors, suffer a bottleneck in manufacturing mono-HP wafers/thin-film materials; hence, exciting results involving mono-HP devices are absent. State-of-the-art optoelectronic HP-based devices are exclusively built using polycrystalline thin films, which are limited in their performance due to issues such as grain-boundary defects, large trap density, and inhomogeneous charge transport. However, these issues can be resolved by utilizing mono-HPs. In this review, we provide in-depth analyses and discussions on the potential of mono-HPs in photovoltaics and transistor applications, and we present the remaining challenges, as well as promising research strategies, to provide a direction for future programs.
This review summarizes the edge-cutting area of the "monocrystalline perovskite wafer/thin film" and their intimate applications in photovoltaics and transistors.
The discounted {0–1} knapsack problem (D{0–1}KP) is a kind of knapsack problem with group structure and discount relationships among items. It is more challenging than the classical 0–1 knapsack ...problem. A more effective hybrid algorithm, the discrete hybrid teaching-learning-based optimization algorithm (HTLBO), is proposed to solve D{0–1}KP in this paper. HTLBO is based on the framework of the teaching-learning-based optimization (TLBO) algorithm. A two-tuple consisting of a quaternary vector and a real vector is used to represent an individual in HTLBO and that allows TLBO to effectively solve discrete optimization problems. We enhanced the optimization ability of HTLBO from three aspects. The learning strategy in the Learner phase is modified to extend the exploration capability of HTLBO. Inspired by the human learning process, self-learning factors are incorporated into the Teacher and Learner phases, which balances the exploitation and exploration of the algorithm. Two types of crossover operators are designed to enhance the global search capability of HTLBO. Finally, we conducted extensive experiments on eight sets of 80 instances using our proposed approach. The experiment results show that the new algorithm has higher accuracy and better stability than do previous methods. Overall, HTLBO is an excellent approach for solving the D{0–1}KP.
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