Property database for single-element doping in ZnO obtained by automated first-principles calculations

Throughout the past decades, doped-ZnO has been widely used in various optical, electrical, magnetic, and energy devices. While almost every element in the Periodic Table was doped in ZnO, the systematic computational study is still limited to a small number of dopants, which may hinder a firm understanding of experimental observations. In this report, we systematically calculate the single-element doping property of ZnO using first-principles calculations. We develop an automation code that enables efficient and reliable high-throughput calculations on thousands of possible dopant configurations. As a result, we obtain formation-energy diagrams for total 61 dopants, ranging from Li to Bi. Furthermore, we evaluate each dopant in terms of n-type/p-type behaviors by identifying the major dopant configurations and calculating carrier concentrations at a specific dopant density. The existence of localized magnetic moment is also examined for spintronic applications. The property database obtained here for doped ZnO will serve as a useful reference in engineering the material property of ZnO through doping. © 2017 The Author(s)131

Novel high-Κ dielectrics for next-generation electronic devices screened by automated ab initio calculations

As the scale of transistors and capacitors in electronics is reduced to less than a few nanometers, leakage currents pose a serious problem to the device's reliability. To overcome this dilemma, high-Κ materials that exhibit a larger permittivity and band gap are introduced as gate dielectrics to enhance both the capacitance and block leakage simultaneously. Currently, HfO2 is widely used as a high-Κ dielectric; however, a higher-Κ material remains desired for further enhancement. To find new high-Κ materials, we conduct a high-throughput ab initio calculation for band gap and permittivity. The accurate and efficient calculation is enabled by newly developed automation codes that fully automate a series of delicate methods in a highly optimized manner. We can, thus, calculate>1800 structures of binary and ternary oxides from the Inorganic Crystal Structure Database and obtain a total property map. We confirm that the inverse correlation relationship between the band gap and permittivity is roughly valid for most oxides. However, new candidate materials exhibit interesting properties, such as large permittivity, despite their large band gaps. Analyzing these materials, we discuss the origin of large Κ values and suggest design rules to find new high-Κ materials that have not yet been discovered. © 2015 Nature Publishing Group All rights reserved124291sciescopu

Hydrogen Evolution Reaction at Anion Vacancy of Two-Dimensional Transition-Metal Dichalcogenides: Ab Initio Computational Screening

The catalytic activity for the hydrogen evolution reaction (HER) at the anion vacancy of 40 2D transition-metal dichalcogenides (TMDs) is investigated using the hydrogen adsorption free energy (Δ<i>G</i>_H) as the activity descriptor. While vacancy-free basal planes are mostly inactive, anion vacancy makes the hydrogen bonding stronger than clean basal planes, promoting the HER performance of many TMDs. We find that ZrSe₂ and ZrTe₂ have similar Δ<i>G</i>_H as Pt, the best HER catalyst, at low vacancy density. Δ<i>G</i>_H depends significantly on the vacancy density, which could be exploited as a tuning parameter. At proper vacancy densities, MoS₂, MoSe₂, MoTe₂, ReSe₂, ReTe₂, WSe₂, IrTe₂, and HfTe₂ are expected to show the optimal HER activity. The detailed analysis of electronic structure and the multiple linear regression results identifies the vacancy formation energy and band-edge positions as key parameters correlating with Δ<i>G</i>_H at anion vacancy of TMDs

Large-area perovskite solar cells employing spiro-Naph hole transport material

Stabilizing the best-performing state-of-the-art perovskite solar cells (PSCs) based on a spiro-OMeTAD hole transport material (HTM), without sacrificing their high power conversion efficiency (PCE) levels, is a challenging task. By exploiting the symmetry-tuned strategy at the molecular level, we have developed spiro-OMeTAD analogues (namely, the spiro-Naph series) with asymmetric phenylnaphthylamine edge units. The new spiro-Naph HTM-based PSC achieved a high PCE of 24.43%, higher than that achieved with spiro-OMeTAD. In addition to excellent stability when soaking the encapsulated device with continuous light, superior device stability was also obtained for the unencapsulated spiro-Naph-based PSC-a PCE of 21.12% was retained in air with similar to 25% relative humidity after 2,000 h and a PCE of 18.79% was retained at an elevated temperature of 60 degrees C after 400 h. We also constructed a spiro-Naph-based large-area module (25 cm(2)) with a PCE of 21.83%