Photoelectronic Responses in Solution-Processed Perovskite CH[3]NH[3]PbI[3] Solar Cells Studied by Photoluminescence and Photoabsorption Spectroscopy

Photoelectronic responses of organic-inorganic hybrid perovskite CH[3]NH[3]PbI[3] on mesoporous TiO[2] electrodes are investigated. On the basis of near-band-edge optical absorption and photoluminescence spectra, the bandgap energy and exciton binding energy as a function of temperature are obtained. The exciton binding energy is much smaller than thermal energy at room temperature, which means that most excitons are thermally dissociated, and optical processes are determined by the photoexcited electrons and holes. We determined the temperature dependence of exciton binding energy, which changes from ~30 meV at 13 K to 6 meV at 300 K. In addition, the bandgap energy and the exciton binding energy show abrupt changes at 150 K due to structural phase transition. Our fundamental optical studies provide essential information for improving the device performance of solar cells based on halide perovskite semiconductors

Guideline for Hereditary Angioedema (HAE) 2010 by the Japanese Association for Complement Research - Secondary Publication

ABSTRACTThis guideline was provided by the Japanese Association for Complement Research targeting clinicians for making an accurate diagnosis of hereditary angioedema (HAE), and for prompt treatment of the HAE patient in Japan. This is a 2010 year version and will be updated according to any pertinent medical advancements

Medical Needs Extraction for Breast Cancer Patients from Question and Answer Services: Natural Language Processing-Based Approach

Background: A large number of patient narratives are available on various web services. As for web question and answer services, patient questions often relate to medical needs, and we expect these questions to provide clues for a better understanding of patients’ medical needs. Objective: This study aimed to extract patients’ needs and classify them into thematic categories. Clarifying patient needs is the first step in solving social issues that patients with cancer encounter. Methods: For this study, we used patient question texts containing the key phrase “breast cancer,“ available at the Yahoo! Japan question and answer service, Yahoo! Chiebukuro, which contains over 60,000 questions on cancer. First, we converted the question text into a vector representation. Next, the relevance between patient needs and existing cancer needs categories was calculated based on cosine similarity. Results: The proportion of correct classifications in our proposed method was approximately 70%. Considering the results of classifying questions, we found the variation and the number of needs. Conclusions: We created 3 corpora to classify the problems of patients with cancer. The proposed method was able to classify the problems considering the question text. Moreover, as an application example, the question text that included the side effect signaling of drugs and the unmet needs of cancer patients could be extracted. Revealing these needs is important to fulfill the medical needs of patients with cancer

Identifying an Optimum Perovskite Solar Cell Structure by Kinetic Analysis: Planar, Mesoporous Based, or Extremely Thin Absorber Structure

Perovskite solar cells have rapidly been developed over the past several years. Choice of the most suitable solar cell structure is crucial to improve the performance further. Here, we attempt to determine an optimum cell structure for methylammonium lead iodide (MAPbI₃) perovskite sandwiched by TiO₂ and spiro-OMeTAD layers, among planar heterojunction, mesoporous structure, and extremely thin absorber structure, by identifying and comparing charge carrier diffusion coefficients of the perovskite layer, interfacial charge transfer, and recombination rates using transient emission and absorption spectroscopies. An interfacial electron transfer from MAPbI₃ to compact TiO₂ occurs with a time constant of 160 ns, slower than the perovskite photoluminescence (PL) lifetime (34 ns). In contrast, fast non-exponential electron injection to mesoporous TiO₂ was observed with at least two different electron injection processes over different time scales; one (60–70%) occurs within an instrument response time of 1.2 ns and the other (30–40%) on nanosecond time scale, while most of hole injection (85%) completes in 1.2 ns. Analysis of the slow charge injection data revealed an electron diffusion coefficient of 0.016 ± 0.004 cm² s^–1 and a hole diffusion coefficient of 0.2 ± 0.02 cm² s^–1 inside MAPbI₃. To achieve an incident photon-to-current conversion efficiency of >80%, a minimum charge carrier diffusion coefficient of 0.08 cm² s^–1 was evaluated. An interfacial charge recombination lifetime was increased from 0.5 to 40 ms by increasing a perovskite layer thickness, suggesting that the perovskite layer suppresses charge recombination reactions. Assessments of charge injection and interfacial charge recombination processes indicate that the optimum solar cell structure for the MAPbI₃ perovskite is a mesoporous TiO₂ based structure. This comparison of kinetics has been applied to several different types of photoactive semiconductors such as perovskite, CdTe, and GaAs, and the most appropriate solar cell structure was identified

Origin of Open-Circuit Voltage Loss in Polymer Solar Cells and Perovskite Solar Cells

Herein, the open-circuit voltage (<i>V</i>_OC) loss in both polymer solar cells and perovskite solar cells is quantitatively analyzed by measuring the temperature dependence of <i>V</i>_OC to discuss the difference in the primary loss mechanism of <i>V</i>_OC between them. As a result, the photon energy loss for polymer solar cells is in the range of about 0.7–1.4 eV, which is ascribed to temperature-independent and -dependent loss mechanisms, while that for perovskite solar cells is as small as about 0.5 eV, which is ascribed to a temperature-dependent loss mechanism. This difference is attributed to the different charge generation and recombination mechanisms between the two devices. The potential strategies for the improvement of <i>V</i>_OC in both solar cells are further discussed on the basis of the experimental data