Trends in open-circuit voltage (Voc), short-circuit current density (Jsc), and energy conversion efficiency have been determined for the n-type AlxGa1-xAs series of photoelectrodes (x = 0.0, 0.09, 0.16, 0.24, 0.31) in contact with CH3CN-ferrocene+/0 and KOH-Se-/2-(aq) electrolytes. Voc increased linearly with increases in bandgap energy (Eg) of the n-AlxGa1-xAs alloy electrodes, with ΔVoc/ΔEg = 0.45 ± 0.04 V eV-1 in CH3CN and 0.41 ± 0.09 V eV-1 in KOH-Se-/2-(aq) at a light intensity sufficient to provide Jsc = 1.0 mA cm-2. Jsc values under solar-simulated illumination decreased monotonically with increasing bandgap energy. The relatively low value of ΔVoc/ΔEg implies decreases in optimal energy conversion efficiency as the mole fraction of Al in the AlxGa1-xAs alloy is increased. This is in contrast to the behavior of the n-GaAsxP1-x alloy series in the same electrolytes. The lower value of ΔKoc/ΔEg for n-AlxGa1-xAs also indicates that predictions of the "common anion rule" in solid-state barriers do not apply to this family of III-V semiconductor/liquid junctions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry