PhotoNow · Discovery and Characterization of Third-Generation Nonlinear Photovoltaics

A central focus of leading investigations, the bulk photovoltaic effect is a nonlinear absorption process that converts light into electrical current intrinsically. The last few years have brought groundbreaking discoveries to the field, including an unprecedented enhancement of the photoresponse driven by a combination of topology and third-order electric-field effects, as well as the first material realization of solar-cell efficiency exceeding the upper-limit of current devices. The nonlinear mechanism is thus in an excellent position to revolutionize the field of solar-cell technologies by opening a fundamentally new route towards highly efficient third-generation photovoltaics. Reaching this landmark requires both a fundamental understanding and a systematic search of materials. In this scenario, first-principles calculations based on density functional theory must play a central role in coming years due to their innate ability to deliver microscopic and material-specific predictions. A first-principles description of nonlinear responses, however, is very complex and contemporary methods need to go far beyond the state-of-the-art for modelling central effects such as third-order contributions. PhotoNow aims at filling this critical gap by developing a first-principles method that correctly incorporates these effects, giving unprecedented access to crucial properties like the energy conversion efficiency. Our methodology will rest upon a Wannier-function technique adaptable to any material, crystallizing in a free software interdisciplinary tool aimed for physicists, chemists and engineers. This major development will allow us to achieve our central goal, namely discovering and characterizing outstanding materials for nonlinear photovoltaics. PhotoNow will carry out a systematic analysis of a wide variety of materials including Weyl semimetals, ferroelectrics and distorted semiconductors, delivering key microscopic understanding and guiding future discoveries.