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Title: Direct solar-to-hydrogen conversion via inverted metamorphic multi-junction semiconductor architectures

Solar water splitting via multi-junction semiconductor photoelectrochemical cells provides direct conversion of solar energy to stored chemical energy as hydrogen bonds. Economical hydrogen production demands high conversion efficiency to reduce balance-of-systems costs. For sufficient photovoltage, water-splitting efficiency is proportional to the device photocurrent, which can be tuned by judicious selection and integration of optimal semiconductor bandgaps. Here, we demonstrate highly efficient, immersed water-splitting electrodes enabled by inverted metamorphic epitaxy and a transparent graded buffer that allows the bandgap of each junction to be independently varied. Voltage losses at the electrolyte interface are reduced by 0.55 V over traditional, uniformly p-doped photocathodes by using a buried p-n junction. Lastly, advanced on-sun benchmarking, spectrally corrected and validated with incident photon-to-current efficiency, yields over 16% solar-to-hydrogen efficiency with GaInP/GaInAs tandem absorbers, representing a 60% improvement over the classical, high-efficiency tandem III-V device.
Authors:
ORCiD logo [1] ;  [1] ;  [2] ;  [1] ; ORCiD logo [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Philipps-Univ. Marburg, Marburg (Germany)
Publication Date:
Report Number(s):
NREL/JA-5900-66837
Journal ID: ISSN 2058-7546
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Nature Energy
Additional Journal Information:
Journal Volume: 2; Journal Issue: 4; Journal ID: ISSN 2058-7546
Publisher:
Nature Publishing Group
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; solar water splitting; inverted metamorphic multijunction semiconductors; III-V semiconductors; devices for energy harvesting; electrocatalysis; hydrogen fuel; solar fuels
OSTI Identifier:
1348150