Tandem cells for efficient photoelectrochemical solar fuels production
Thomas Hannappel a, M. A. Zare Pour a, S. Shekarabi a, A. Paszuk a, D. Ostheimer a, W. Jaegermann a, W.-H. Cheng b c, O. Romanyuk d, E. Runge a, F. Dimroth e, H. A. Atwater c
a Ilmenau University of Technology, Institute of Physics, Germany
b Dep. of Materials Science and Technology, National Cheng Kung University, Taiwan
c California Institute of Technology, Dep. of Applied Physics and Material Science, USA
d Institute of Physics of the Czech Academy of Sciences, Czech Republic
e Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany
Invited Speaker Session, Thomas Hannappel, presentation 150
Publication date: 6th February 2024

Epitaxial semiconductors involving III-V compounds and silicon promise the highest performance levels in PV applications such as in solar cells and photoelectrochemical cells [1-3]. However, highest performance in solar energy conversion can only be achieved, when using optimum absorber layers and advanced contact formation for electronic and chemical passivation, i.e. for the protection of the solid-liquid interface against corrosion as well as impeding interfacial non-radiative recombination. In order to address the surface and interface properties of III-V semiconductor layer structures in relation to their performance, we present the synthesis, theoretical modelling and properties of critical and well-defined interfaces such as GaInP/AlInP [4] or GaInP/GaN [5]. Here, lattice matched n-type GaN or AlInP(100) charge selective contacts are prepared on n-p GaInP(100) top absorbers in highest-efficiency III–V multijunction solar or photoelectrochemical cells, where the cell performance can be greatly limited by missing electron selectivity and detrimental valance band offsets. Hence, understanding of the atomic and electronic properties of the heterointerfaces, for instance, is crucial for the reduction of photocurrent losses in III–V multijunction devices. We discuss the essential considerations on the properties of critical interfaces in relation to photoelectrochemical cells from a conceptual and from a theoretical modeling point of view assuming mostly idealized surface conditions. We also address latest progress on the important III-V/Si interface, modifications by fine-tuning of the preparation and describe experimental model experiments on the surface reactivity of III-phosphide surfaces to H2O exposure. These different surface science approaches are then related to photoelectrochemical cells for H2 evolution and CO2 reduction using different III-V based tandem cells and providing highest conversion yields.

We express our gratitude for the financial assistance provided by the National Science Foundation and the German Research Foundation (NSF-DFG project no. HA 3096/19-1) and German Federal Ministry of Education and Research (DEPECOR project no. 033RC021A and H2Demo project no. 03SF0619I).

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