量子ドット太陽電池とペロブスカイト太陽電池における界面修飾と界面電荷ダイナミクス

The present globalization of energy shortage and environmental pollution issues have posed a grave menace to human survival and development. Finding a viable supply of clean, renewable energy is one of the most daunting challenges facing the world. Solar cells as devices that convert solar energy into electricity is the focus of the whole society. However, conventional solar cells have had limited impact in meeting this challenge because of their high pollution, high cost and low power conversion efficiencies. Recently, colloid quantum dot solar cells (CQDSCs) and perovskite solar cells (PSCs) as new generation solar cells have been attracting immense attention owing to their inexpensive solution-based techniques and high theoretical power conversion efficiency. However, stability is still a big problem for CQDSCs and PSCs, and charge dynamics in those solar cells are not clear. To obtain stable CQDSCs and PSCs through interface modification, and reveal the charge dynamics in those solar cells are the central aim of this thesis. This thesis investigated the surface ligand dependent charge carrier dissociation, charge carrier transmission and recombination of CQDSCs, and used novel hole transport materials to modify the interface of CQDSCs and PSCs to reduce the interfacial recombination in CQDSCs and PSCs. In this thesis, I explore a method to obtain air stable PbSe CQDs and surface ligand dependent exciton dissociation, recombination, photovoltaic property, and stability of PbSe solid films and CQDSCs. I select four short ligands, that is, two organic ligands 1,2-ethanedithiol (EDT) and 3-mercaptopropionic acid (MPA); two inorganic ligand cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium iodide (TBAI) to investigate the ligand-dependent air stability, energy level shift, the exciton dissociation, and photovoltaic properties of PbSe CQDSCs. In addition, the charge transfer rate, recombination processes and carrier lifetimes in these CQDSCs were also revealed through ultrafast transient absorption (TA) spectra, and open-circuit transient voltage (Voc) decay measurements. We also explore a method to suppress the interfacial recombination at QDs/Au electrode in CQDSCs by using organic small molecule. We develop a novel donor-π-donor (D-π-D) organic small molecule bis-triphenylamine with spiro(fluorene-9,9’-xanthene) as the conjugated system, named BTPA-4, as a hole selective layer (HSL) in the PbS CQDSCs. We found that the introduction of BTPA-4 as HSL can enhance the open-circuit voltage (Voc), prolong the effective carrier lifetime, reduce the interfacial recombination at PbS QDs/Au interface, and hence improve the device performance. Furthermore, the PbS CQDSCs with BTPA-4 possessed a noticeably stable property for over 100 days of storage under ambient atmosphere that has been the Achilles\u27 heel of other organic HSL for CQDSCs. We also focus on hole transport materials and the interfacial recombination in PSCs. Three triphenylamine-based hole-transport materials (HTMs), named BTPA-4, BTPA-5 and BTPA-6, were used into PSCs. BTPA-6 with four substituted triphenylamine units exhibited a better solar cell performance than BTPA-4 and BTPA-5 which contain two substituted triphenylamine units. BTPA-6 achieved a PCE of 14.4% which nearly matches Spiro-OMeTAD (15.0%). The order of the recombination resistance was found to be in the order of BTPA-4 < BTPA-5 < BTPA-6 < Spiro-OMeTAD, indicating that the electron blocking capability of the HTM is in this order. This trend agrees with the Voc trend of their corresponding solar cells. In addition, BTPA-6 based devices showed better long-term stability than that with Spiro-OMeTAD, which can partially be attributed to the hydrophobicity of BTPA-6 is better than that of Spiro-OMeTAD. The goal of above experiments is to gain a more complete understanding of charge carrier dynamics in CQDSCs and PSCs, so that more efficient materials and architecture for solar cells can be designed in the future.電気通信大学201

Stability and Sensitivity Analysis of a Plant Disease Model with Continuous Cultural Control Strategy

In this paper, a plant disease model with continuous cultural control strategy and time delay is formulated. Then, how the time delay affects the overall disease progression and, mathematically, how the delay affects the dynamics of the model are investigated. By analyzing the transendental characteristic equation, stability conditions related to the time delay are derived for the disease-free equilibrium. Specially, when R0=1, the Jacobi matrix of the model at the disease-free equilibrium always has a simple zero eigenvalue for all τ≥0. The center manifold reduction and the normal form theory are used to discuss the stability and the steady-state bifurcations of the model near the nonhyperbolic disease-free equilibrium. Then, the sensitivity analysis of the threshold parameter R0 and the positive equilibrium E* is carried out in order to determine the relative importance of different factors responsible for disease transmission. Finally, numerical simulations are employed to support the qualitative results

Alchemical and structural distribution based representation for improved QML

We introduce a representation of any atom in any chemical environment for the generation of efficient quantum machine learning (QML) models of common electronic ground-state properties. The representation is based on scaled distribution functions explicitly accounting for elemental and structural degrees of freedom. Resulting QML models afford very favorable learning curves for properties of out-of-sample systems including organic molecules, non-covalently bonded protein side-chains, (H$_2$O)$_{40}$-clusters, as well as diverse crystals. The elemental components help to lower the learning curves, and, through interpolation across the periodic table, even enable "alchemical extrapolation" to covalent bonding between elements not part of training, as evinced for single, double, and triple bonds among main-group elements

Stability and Sensitive Analysis of a Model with Delay Quorum Sensing

This paper formulates a delay model characterizing the competition between bacteria and immune system. The center manifold reduction method and the normal form theory due to Faria and Magalhaes are used to compute the normal form of the model, and the stability of two nonhyperbolic equilibria is discussed. Sensitivity analysis suggests that the growth rate of bacteria is the most sensitive parameter of the threshold parameter R0 and should be targeted in the controlling strategies

EXPERIMENTAL STUDY ON THE SEISMIC DAMAGE OF AEOLIAN SAND CONCRETE COLUMNS WITH DIFFERENT REINFORCEMENTS

Aeolian sand is a kind of natural material with abundant reserves and a low price. Many scholars have conducted extensive studies on the engineering applications of aeolian sand. This paper addresses the seismic damage behaviour of aeolian sand concrete columns to promote the application of aeolian sand in frame structures. A total of 5 aeolian sand concrete column specimens with different reinforcements were studied using cyclic loading tests. The failure modes, stiffness degradation, bearing capacity, hysteresis peculiarity, ductility, and energy consumption of the specimens were analysed and compared. Then, applicable damage models of the specimens were proposed. The study results prove that the seismic damage behaviour of the specimens increases with the increase of longitudinal reinforcement percentage and with the transverse steel ratio when the replacement percentage of aeolian sand is constant. Additionally, the damage model which is revised in this paper agrees well with the test results. It can be used to assess the degree of damage to the aeolian sand concrete columns

Therapeutic effects of combined meloxicam and glucosamine sulfate treatment on patients with osteoarthritis, and its effect on serum CTX-Ⅰ, CTX-Ⅱ, COMP and MMP-3

Purpose: To study the therapeutic influence of meloxicam-glucosamine sulfate combination in patients with osteoarthritis and their effect on serum CTX-I, CTX-II, COMP and MMP-3. Methods: A total of 88 patients with osteoarthritis were assigned to control (n = 44) and treatment groups (n = 44), using the random number table method. Control group was given 7.5 mg of meloxicam, while treatment group received 0.5 g of glucosamine sulfate capsule in addition to meloxicam. Both groups were treated continuously for 8 weeks. Serum levels of C-terminal telopeptide of type I collagen (CTX-I), C-terminal telopeptide of type II collagen (CTX-II), cartilage oligomeric matrix protein (COMP) and matrix metalloproteinase-3 (MMP-3) were compared for the two groups after treatment. Results: Lysholm score significantly increased in the two groups after treatment. Serum CTX-I, CTX-II, COMP and MMP-3 in the two groups were significantly lower than before treatment, but the reductions were more pronounced in the treatment group (p &lt; 0.05). During treatment, mild vomiting and pruritus of the skin appeared in both groups, but these were relieved after symptomatic treatment without any serious adverse reactions. Conclusion: Treatment with a combination of meloxicam and glucosamine sulfate produces significant beneficial effects in patients with osteoarthritis by reduction of clinical symptoms, pain relief and reduction of serum CTX-I, CTX-II, MMP-3 and COMP

Mixed Sn–Ge Perovskite for Enhanced Perovskite Solar Cell Performance in Air

Lead-based perovskite solar cells have gained ground in recent years, showing efficiency as high as 20%, which is on par with that of silicon solar cells. However, the toxicity of lead makes it a nonideal candidate for use in solar cells. Alternatively, tin-based perovskites have been proposed because of their nontoxic nature and abundance. Unfortunately, these solar cells suffer from low efficiency and stability. Here, we propose a new type of perovskite material based on mixed tin and germanium. The material showed a band gap around 1.4–1.5 eV as measured from photoacoustic spectroscopy, which is ideal from the perspective of solar cells. In a solar cell device with inverted planar structure, pure tin perovskite solar cell showed a moderate efficiency of 3.31%. With 5% doping of germanium into the perovskite, the efficiency improved up to 4.48% (6.90% after 72 h) when measured in air without encapsulation

Genome-Wide Characterization of Endogenous Retroviruses in Bombyx mori Reveals the Relatives and Activity of env Genes

Endogenous retroviruses (ERVs) are retroviral sequences that remain fixed in the host genome, where they could play an important role. Some ERVs have been identified in insects and proven to have infectious properties. However, no information is available regarding Bombyx mori ERVs (BmERVs) to date. Here, we systematically identified 256 potential BmERVs in the silkworm genome via a whole-genome approach. BmERVs were relatively evenly distributed across each of the chromosomes and accounted for about 25% of the silkworm genome. All BmERVs were classified as young ERVs, with insertion times estimated to be less than 10 million years. Seven BmERVs possessing the env genes were identified. With the exception of the Orf133 Helicoverpa armigera nuclear polyhedrosis virus, the env sequences of BmERVs were distantly related to genes encoding F (Fa and Fb) and GP64 proteins from Group I and Group II NPVs. In addition, only the amino acid sequence of the BmERV-21 envelope protein shared a similar putative furin-like cleavage site and fusion peptide with Group II baculoviruses. All of the env genes in the seven BmERVs were verified to exist in the genome and be expressed in the midgut and fat bodies, which suggest that BmERVs might play an important role in the host biology

Ultrafast selective extraction of hot holes from cesium lead iodide perovskite films

Lead halide perovskites have some unique properties which are very promising for optoelectronic applications such as solar cells, LEDs and lasers. One important and expected application of perovskite halide semiconductors is solar cell operation including hot carriers. This advanced solar cell concept allows overcoming the Shockley–Queisser efficiency limit, thereby achieving energy conversion efficiency as high as 66% by extracting hot carriers. Understanding ultrafast photoexcited carrier dynamics and extraction in lead halide perovskites is crucial for these applications. Here, we clarify the hot carrier cooling and transfer dynamics in all-inorganic cesium lead iodide (CsPbI3) perovskite using transient absorption spectroscopy and Al2O3, poly(3-hexylthiophene-2,5-diyl) (P3HT) and TiO2 as selective contacts. We find that slow hot carrier cooling occurs on a timescale longer than 10 ps in the cases of CsPbI3/Al2O3 and CsPbI3/ TiO2, which is attributed to hot phonon bottleneck for the high photoexcited carrier density. An efficient ultrafast hole transfer from CsPbI3 to the P3HT hole extracting layer is observed. These results suggest that hot holes can be extracted by appropriate selective contacts before energy dissipation into the halide perovskite lattice and that CsPbI3 has a potential for hot carrier solar cell applications