SEMI-MONOLITHIC DEVICES FOR PHOTOELECTROCHEMICAL HYDROGEN PRODUCTION IN THIS PROJECT WE PROPOSE TO DEVELOP A NOVEL AND SCALABLE INTEGRATION SCHEME TO COMBINE PROMISING MATERIAL CLASSES REGARDLESS OF THEIR THERMAL, PHYSICAL, AND/OR CHEMICAL COMPATIBILITY INTO LOW-COST MULTI-JUNCTION (MJ) PEC DEVICES WITH AN UPPER STH EFFICIENCY LIMIT OF 25%. SUCH SCHEME, PIONEERED BY HNEI AND KNOWN AS SEMI-MONOLITHIC INTEGRATION, RELIES ON 2D LAYER-ASSISTED EXFOLIATION AND ROOM TEMPERATURE BONDING TECHNIQUES TO TRANSFER FULLY PROCESSED SUB-CELLS FROM THEIR ORIGINAL SUBSTRATES ONTO NEW HANDLES. BY DESIGN, SEMI-MONOLITHIC INTEGRATION ALLOWS TO CIRCUMVENT ALL MATERIAL INCOMPATIBILITIES, ENABLING NEW MJ ARCHITECTURES OTHERWISE NOT POSSIBLE WITH CONVENTIONAL MONOLITHIC INTEGRATION. THE CENTRAL GOAL OF THIS PROJECT WILL BE TO USE THE CONCEPT OF SEMI-MONOLITHIC INTEGRATION TO COMBINE TWO HIGHLY PROMISING LOW-COST MATERIAL CLASSES, CHALCOPYRITES AND PEROVSKITES, INTO HIGH DEFICIENCY AND DURABLE MJ PEC DEVICES. EXPLOITING OUR PRELIMINARY RESULTS OBTAINED WITH ALL-CHALCOPYRITE TRIPLE JUNCTION MJ DEVICES, WE WILL FURTHER IMPROVE THE SEMI-MONOLITHIC CONCEPT TO CREATE EFFICIENT ALL-CHALCOPYRITE AND PEROVSKITE/CHALCOPYRITE MJ PEC DEVICES, AIMING FOR STH EFFICIENCY > 15%. ALSO, WE WILL EMPLOY NEW POLYMER-BASED PROTECTION LAYERS COUPLED WITH PROVEN INORGANIC COATING STRATEGIES (E.G., MOS2) TO ACHIEVE OVER 1,000 HOURS OF CONTINUOUS OPERATION WITH SEMI-MONOLITHICALLY INTEGRATED MJ DEVICES. WITH SUPPORT FROM EXPERTS WITHIN THE HYDROGEN CONSORTIUM, WE WILL USE OUR ESTABLISHED MULTI-DISCIPLINARY APPROACH WITH INTEGRATED THEORY, SYNTHESIS, AND CHARACTERIZATION TO ACCELERATE MATERIAL AND DEVICE DEVELOPMENT TOWARDS MEETING DOE’S ULTIMATE HYDROGEN PRODUCTION COST.