Imperfections in organometal halide perovskite films such as grain boundaries (GBs), defects, and traps detrimentally cause significant nonradiative recombination energy loss and decreased power conversion efficiency (PCE) in solar cells. Here, a simple layer-by-layer fabrication process based on air exposure followed by thermal annealing is reported to grow perovskite films with large, single-crystal grains and vertically oriented GBs. The hole-transport medium Spiro-OMeTAD is then infiltrated into the GBs to form vertically aligned bulk heterojunctions. Due to the space-charge regions in the vicinity of GBs, the nonradiative recombination in GBs is significantly suppressed. The GBs become active carrier collection channels. Thus, the internal quantum efficiencies of the devices approach 100% in the visible spectrum range. The optimized cells yield an average PCE of 16.3 ± 0.9%, comparable to the best solution-processed perovskite devices, establishing them as important alternatives to growing ideal single crystal thin films in the pursuit toward theoretical maximum PCE with industrially realistic processing techniques.

Realizing the commercialization of high-performance and robust perovskite solar cells urgently requires the development of economically scalable processing techniques. Here we report a highthroughput ultrasonic spray-coating (USC) process capable of fabricating perovskite film-based solar cells on glass substrates with power conversion efficiency (PCE) as high as 13%.Perovskite films with high uniformity, crystallinity, and surface coverage are obtained in a single step. Moreover, we report USC processing on TiO 2 /ITO-coated polyethylene terephthalate (PET) substrates to realize flexible perovskite solar cells with PCE as high as 8.1% that are robust under mechanical stress. In this case, a photonic curing technique was used to achieve a highlyconductive TiO 2 layer on flexible PET substrates for the first time. The high device performance and reliability obtained by this combination of USC processing with optical curing appears very promising for roll-to-roll manufacturing of high-efficiency, flexible perovskite solar cells. -halide perovskite solar cells, with power conversion efficiencies (PCEs) rapidly reaching circa 20%, 1-3 are one of the most promising, next-generation photovoltaic technologies due to their excellent material properties, including long carrier diffusion lengths 4 and large absorption coefficients. 5 To achieve high-quality perovskite films, a variety of deposition techniques, such as thermal evaporation, 6-8 single-step spin-coating, 9,10 layer-by-layer or two-step coating, 11,12 and vapor-assisted 13 processes have been developed. However, one major disadvantage of most laboratory-scale techniques is that they are incompatible with lowcost, roll-to-roll processing envisioned for large-scale manufacturing. Existing scalable processing techniques include ink-jet printing, slot-die coating, blade-coating, screen printing, and ultrasonic spray-coating. 14-21Among these cost-effective roll-to-roll compatible processes, ultrasonic spray-coating (USC) is one of the most promising that has been successfully exploited for the fabrication of various organic electronic devices including light emitting diodes, 22 photovoltaics, 23,24 photodetectors, 25 and field-effect transistors. 26 The overall advantage of USC is its ability to simultaneously provide high throughput, better control over directional deposition, efficient use of materials, uniform film coverage, compatibility with variety of substrates, with the potential for the deposition of continuous layers without dissolution of underlying layers. 23,[26][27][28] Recently, the USC process was demonstrated to deposit perovskite thin films on glass substrates, and the resulting devices showed an average PCE of 7. 8%. 29 However, considering the diverse application potential for thin film perovskites, it is highly important to demonstrate the fabrication of high-performance devices on light-weight and flexible substrates using scalable techniques. So far, one major challenge for the fabrication of solar cells on plastic substrates is their ...

A quantitative structure-activity relationship (QSAR) methodology based on hierarchical clustering was developed to predict toxicological endpoints. This methodology utilizes Ward's method to divide a training set into a series of structurally similar clusters. The structural similarity is defined in terms of 2-D physicochemical descriptors (such as connectivity and E-state indices). A genetic algorithm-based technique is used to generate statistically valid QSAR models for each cluster (using the pool of descriptors described above). The toxicity for a given query compound is estimated using the weighted average of the predictions from the closest cluster from each step in the hierarchical clustering assuming that the compound is within the domain of applicability of the cluster. The hierarchical clustering methodology was tested using a Tetrahymena pyriformis acute toxicity data set containing 644 chemicals in the training set and with two prediction sets containing 339 and 110 chemicals. The results from the hierarchical clustering methodology were compared to the results from several different QSAR methodologies.

The high Z chalcohalides HgQI (Q = S, Se, and Te) can be regarded as of antiperovskite structure with ordered vacancies and are demonstrated to be very promising candidates for X- and γ-ray semiconductor detectors. Depending on Q, the ordering of the Hg vacancies in these defect antiperovskites varies and yields a rich family of distinct crystal structures ranging from zero-dimensional to three-dimensional, with a dramatic effect on the properties of each compound. All three HgQI compounds show very suitable optical, electrical, and good mechanical properties required for radiation detection at room temperature. These compounds possess a high density (>7 g/cm) and wide bandgaps (>1.9 eV), showing great stopping power for hard radiation and high intrinsic electrical resistivity, over 10 Ω cm. Large single crystals are grown using the vapor transport method, and each material shows excellent photo sensitivity under energetic photons. Detectors made from thin HgQI crystals show reasonable response under a series of radiation sources, including Am andCo radiation. The dimensionality of Hg-Q motifs (in terms of ordering patterns of Hg vacancies) has a strong influence on the conduction band structure, which gives the quasi one-dimensional HgSeI a more prominently dispersive conduction band structure and leads to a low electron effective mass (0.20 m). For HgSeI detectors, spectroscopic resolution is achieved for both Am α particles (5.49 MeV) andAm γ-rays (59.5 keV), with full widths at half-maximum (FWHM, in percentage) of 19% and 50%, respectively. The carrier mobility-lifetime μτ product for HgQI detectors is achieved as 10-10 cm/V. The electron mobility for HgSeI is estimated as 104 ± 12 cm/(V·s). On the basis of these results, HgSeI is the most promising for room-temperature radiation detection.

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