Cofrequency Resonance Enhanced GaAs Photoelectrode Performance and Charge Transfer Characteristics under 740 nm Illumination

Abstract The efficiency of semiconductor catalysts and solar cells in photovoltaic devices and photoelectrochemical assemblies is largely determined by their absorption characteristics in the visible region, especially at longer wavelengths. In this paper, we systematically investigate the in-situ electrochemical characterization and the open-circuit voltage (Voc) of GaAs electrodes and GaInP/GaAs/Ge solar cells under 430, 480, 565, 740, and 808 nm illumination, respectively, and found that their actions of photogenerated charge generation, separation, and transfer were significantly dependent on wavelength. The photocurrent density under 740 nm illumination reached 4.5 mA, which was three times that under 565 nm irradiation at the same photon flux. The charge transfer resistance (Rct) under the 740 nm illumination reduces to one-sixth from 31.89 KΩ to 6.05 KΩ, which is also superior to the datum under 565 and 808 nm. The maximum sensitivity coefficients were 2.11 × 10–3 V·(μmol·s–1·m–2)−1 at 740 nm, which was 4 times that at 808 nm illumination. The profound wavelength sensitivity and very significant cofrequency resonance effect were found under 740 nm irradiation, which indicated that the photon energy conversion was enhanced, possibly by spin-orbit splitting and higher-energy critical-point transition in GaAs, enabling resonant energy transfer via enhanced interband transitions through coherent superposition of single-photon wavefunctions.