Hong, Sukkyu Woo, Seungwan Son, Hoki Shin, Hyun-Beom Yeon, Eungbeom Mo, Jeongeun Jung, Dae hwan Jang, Ho Won Kang, Ho Kwan Lee, Sung-Min Choi, Won Jun 2026-03-09T05:30:12Z 2026-03-09T05:30:12Z 2026-03-09 2026-03 1614-6832 https://pubs.kist.re.kr/handle/201004/154411 Monolithic III–V multijunction photovoltaics are promising candidates for both space power systems and solar-to-chemical energy conversion, yet their deployment in flexible, chemically aggressive, and radiation-rich environments requires simultaneous control of epitaxial quality, conformability, and barrier properties. Here, we present a flexible InGaP/GaAs/InGaAs triple-junction platform that addresses these requirements within a single device architecture. The optimized epitaxial stack and its growth process enable almost fully relaxed subcells with low dislocation density, supporting power conversion efficiencies above 33% under AM1.5G and ∼31% under AM0, even after transferring the epitaxial stack to a thin plastic substrate to improve mechanical compliance. To ensure environmental robustness, the flexible triple-junction cells are encapsulated with an ultrathin glass sheet that provides strong protection against aqueous and strongly alkaline conditions, as well as against high-energy proton and electron irradiation. By exploiting the high output voltage and durability of this platform, bias-free electrocatalysis with formate as the predominant product is demonstrated using a simple electrocatalyst configuration. These results establish a unified III–V multijunction photovoltaic architecture that couples space-relevant efficiency, flexibility, and radiation hardness with chemical durability suitable for unassisted solar-to-chemical conversion, offering a versatile route toward next-generation terrestrial and space energy systems. English Wiley-VCH Verlag InGaP/GaAs/InGaAs Multijunction Flexible Photovoltaics With Chemical Robustness and Radiation Hardness for Unassisted Electrocatalysis and Space Applications Article 10.1002/aenm.202506763 1 Advanced Energy Materials Advanced Energy Materials N scie scopus Chemistry, Physical Energy & Fuels Materials Science, Multidisciplinary Physics, Applied Physics, Condensed Matter Chemistry Energy & Fuels Materials Science Physics Article; Early Access ELECTRON-RADIATION SOLAR-CELLS PROTON EFFICIENCY REDUCTION WATER CO chemical robustness flexible solar cells III-V multijunction photovoltaics radiation hardness unassisted electrocatalysis