Robust Molecular Dipole Induced Surface Functionalization of Inorganic Perovskites for Efficient Solar Cells

CsPbI3 inorganic perovskite shows high potential for single-junction or tandem solar cells due to its suitable bandgap energy (Eg=~1.7 eV), but defect-assisted nonradiative recombination and unmatched interfacial band alignment within...

Kernel Charge Equilibration: Efficient and Accurate Prediction of Molecular Dipole Moments with a Machine-Learning Enhanced Electron Density Model

State-of-the-art machine learning (ML) interatomic potentials use local representations of atomic environments to ensure linear scaling and size-extensivity. This implies a neglect of long-range interactions, most prominently related to electrostatics. To overcome this limitation, we herein present a ML framework for predicting charge distributions and their interactions termed kernel Charge Equilibration (kQEq). This model is based on classical charge equilibration models like QEq, expanded with an environment dependent electronegativity. In contrast to previously reported neural network models with a similar concept, kQEq takes advantage of the linearity of both QEq and Kernel Ridge Regression to obtain a closed-form linear algebra expression for training the models. Furthermore, we avoid the ambiguity of charge partitioning schemes by using dipole moments as reference data. As a first application, we show that kQEq can be used to generate accurate and highly data-efficient models for molecular dipole moments.

Structural Variants of RM734 in the Design of Splay Nematic Materials

<p><b>Structural Variants of <i>RM734</i> in the Design of Splay Nematic Materials</b></p><p></p><p>The recent discovery of the splay nematic phase, a new nematic polymorph that has been found to be both polar and ferroelectric, is the lead paragraph in an entirely new chapter in the history of liquid crystals. The potential for transformative applications utilizing this state of matter – such as photonics, non-linear optics, memory applications and so on - can only be met with significant improvements in the temperature range of existing materials such as 4-(4-nitrophenoxycarbonyl)phenyl 4-methoxy-2-methoxybenzoate (<i>RM734</i>). Herein we present several families of materials which are structurally related to the archetypal new nematic material, <i>RM734</i>, including the first non-rod-like materials within the context of the splay nematic phase. We find that the incidence (or absence) of this new nematic variant in a designer material cannot be easily rationalized in terms of molecular dipole moment or polarizability. However, mixture formulation shows promise for the engineering of materials with improved working temperature ranges. </p><b></b><p></p>