Integration of Multijunction Absorbers and Catalysts for Efficient Solar‐Driven Artificial Leaf Structures: A Physical and Materials Science Perspective
Thomas Hannappel, Sahar Shekarabi, Wolfram Jaegermann, Erich Runge, Jan P. Hofmann, Roel van de Krol, Matthias M. May, Agnieszka Paszuk, Franziska Heß, Arno Bergmann, Andreas Bund, Christian Cierpka, Christian Dreßler, Fabio Dionigi, Dennis Friedrich, Marco Favaro, Stefan Krischok, Mario Kurniawan, Kathy Lüdge, Yong Lei, Beatriz Roldán Cuenya, Peter Schaaf, Rüdiger Schmidt‐Grund, W. G. Schmidt, Peter Strasser, Eva Unger, Manuel Vásquez-Montoya, Dong Wang, Hongbin Zhang
Abstract
Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar‐driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge‐based design rules, and scalable engineering strategies. Herein, competitive artificial leaf devices for water splitting, focusing on multiabsorber structures to achieve solar‐to‐hydrogen conversion efficiencies exceeding 15%, are discussed. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10–20 mA cm −2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so‐called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Herein, corresponding research efforts to produce green hydrogen with unassisted solar‐driven (photo‐)electrochemical devices are discussed and reported.