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Functional oxides on silicon have been the subject of in-depth research for more than 20 years. Much of this research has been focused on the quality of the integration of materials due to their intrinsic thermodynamic incompatibility, which has hindered the flourishing of the field of research. Nevertheless, growth of epitaxial transition metal oxides on silicon with a sharp interface has been achieved by elaborated kinetically controlled sequential deposition while the crystalline quality of different functional oxides has been considerably improved. In this Research Update, we focus on three applications in which epitaxial ferroelectric oxides on silicon are at the forefront, and in each of these applications, other aspects of the integration of materials play an important role. These are the fields of piezoelectric microelectromechanical system devices, electro-optical components, and catalysis. The overview is supported by a brief analysis of the synthesis processes that enable epitaxial growth of oxides on silicon. This Research Update concludes with a theoretical description of the interfaces and the possibility of manipulating their electronic structure to achieve the desired coupling between (ferroelectric) oxides and semiconductors, which opens up a remarkable perspective for many advanced applications. © 2021 Author(s).

Copyright © 2020 American Chemical Society. Degradation due to electron beam exposure has posed a challenge in the use of electron microscopy to probe halide perovskite materials and devices. In this study, the interaction between the electron beam and the perovskite across acceleration voltages and at low probe currents is investigated in a scanning electron microscope (SEM) by monitoring the electron-beam-induced current (EBIC) response in perovskite solar cells in a plan-view configuration. SEM probe conditions are identified where dozens of repeated scans over a single region of the perovskite solar cell induce minimal electronic degradation. Overall, the induced current response of the perovskite device is found to strongly depend upon the beam condition: Rapid decay occurs at high beam powers, the current activates at the lowest beam powers, and a newfound quasi-steady response is revealed at intermediate beam conditions. A quantitative window for the successful conduction of e-beam studies with minimal electronic degradation is revealed by evaluating induced current response over a wide range of perovskite devices, which invites broader use of SEM-based characterization techniques, including EBIC, as powerful techniques for correlative microscopy investigations.

Lead halide perovskites are among the most exciting classes of optoelectronic materials due to their unique ability to form high‐quality crystals with tunable bandgaps in the visible and near‐infrared using simple solution precipitation reactions. This facile crystallization is driven by their ionic nature; just as with other salts, it is challenging to form amorphous halide perovskites, particularly in thin‐film form where they can most easily be studied. Here, rapid desolvation promoted by the addition of acetate precursors is shown as a general method for making amorphous lead halide perovskite films with a wide variety of compositions, including those using common organic cations (methylammonium and formamidinium) and anions (bromide and iodide). By controlling the amount of acetate, it is possible to tune from fully crystalline to fully amorphous films, with an interesting intermediate state consisting of crystalline islands embedded in an amorphous matrix. The amorphous lead halide perovskite has a large and tunable optical bandgap. It improves the photoluminescence quantum yield and lifetime of incorporated crystalline perovskite, opening up the intriguing possibility of using amorphous perovskite as a passivating contact, as is currently done in record efficiency silicon solar cells.

Though generally reliable, silicon solar modules can be subject to unforeseen degradation, leading to a duty life shorter than the expected 25-year life cycle. Potential-induced degradation (PID) has proven difficult to characterize and study. This dissertation is dedicated to developing a physical model to understand the kinetics of PID of the shunting type, and explain the factors that may lead to the design of PID-robust modules.A bias-temperature stress (BTS) methodology to study ion migration in dielectric films is presented, which accounts for the contribution of bulk traps in the dielectric. Using this method, an Arrhenius relationship for the diffusivity of Na+ in SiNx is determined, for which the prefactor is D0=1.4E-14 cm^2/s, and the activation energy is Ea = 0.14 eV, with a 95% confidence interval of [0.07, 0.21] eV. Based on this result, we bound the transit time of sodium ions through highly resistive SiNx anti-reflective coatings, within 1 h and 2 days, under temperature and electric fields relevant to PV operation.A numerical solution to the coupled Poisson-Nernst-Planck system of equations is presented, based on the finite element method (FEM), that can accurately simulate ionic transport in dielectrics and stacks of materials. The FEM implementation adequately describes the accumulation of charge in the semiconductor interface of metal-insulator-semiconductor capacitors (MIS). Using this model, we evaluate diffusion coefficients of Na+ in SiO2 under BTS conditions. A methodology to simulate PID degradation in PV modules is derived, which uses the result from the ion transport model to simulate the characteristic J-V of the devices. PID is adequately described by the presence of metallic shunt at the p-n junction of the cell, for which, the metal conductivity depends on the sodium concentration. An upper bound for the diffusivity of Na in stacking faults that result in PID is estimated to be 1E-14 cm^2/s, based on comparison of the simulated PID tim

We demonstrate an oxide-stabilized III-V photoelectrode architecture for solar fuel production from water in neutral pH. For this tunable architecture we demonstrate 100% Faradaic efficiency for hydrogen evolution, and incident photon-to-current efficiencies (IPCE) exceeding 50%. High IPCE for hydrogen evolution is a consequence of the low-loss interface achieved via epitaxial growth of a thin oxide on a GaAs solar cell. Developing optimal energetic alignment across the interfaces of the photoelectrode using well-established III-V technology is key to obtaining high performance. This advance constitutes a critical milestone towards efficient, unassisted fuel production from solar energy., Massachusetts Institute of Technology. Battelle Postdoctoral Program, MIT Energy Initiative, MIT & Masdar Institute Cooperative Program