Zinc Selenide Photoelectrodes: Efficient Radiative Recombination in a Stable Photoelectrochemical Cell

Abstract

Photoluminescence (PL) and electroluminescence (EL) from single-crystal, n-type, Al-doped ZnSe (ZnSe:A1) electrodes have been studied. These samples exhibit both edge emission (k~a~ ~ 460 nm) and subbandgap emission when excited at several ultrabandgap wavelengths. The latter PL band is particularly intense, with a measured radiative quantum yield of -10 -I to 10-~; the transition appears to be at least partially self-activated (SA) in origin, based on previously reported PL data. Excited-state communication involving the two emissive states is inferred from time-resolved PL measurements. Stable photoelectrochemical cells (PEC's) can be constructed from n-ZnSe:A1 electrodes and aqueous diselenide or ditelluride electrolytes. Applied potential quenches both of the photoanodes' PL bands roughly in parallel. The extent of PL quenching is consistent with a dead-layer model previously used to describe quenching in Au-ZnSe Schottky diodes. When used as a dark cathode in aqueous, alkaline peroxydisulfate electrolyte, EL from ZnSe:A1 electrodes is observed. PL and EL spectral distributions are similar and indicate that the same emissive excited states are populated in the two experiments. Measured EL efficiencies, -10 -4 to 10 -6 at -2.2 and -1.8V vs. SCE, respectively, are much smaller than PL efficiencies. Possible sources of the discrepancies are discussed.Keen interest in photoelectrochemical cells (PEC's) has focused attention on the excited-state properties of the semiconductor electrodes which serve as the key element of these devices (1). We and others have studied photoluminescence (PL) and electroluminescence (EL) from a variety of II-VI and III-V semiconductor electrodes in an effort to determine the effect of PEC parameters on the solids' excited-state deactivation routes (2). In general, measured radiative quantum yields, ~br, of these materials have been small, -10-3-10 -~. We describe in this paper an electrode, n-ZnSe:A1, whose emission competes favorably (~br -10-1-10 -2) with other deactivation paths in stable, efficient PEC's. As observed with other semiconductor electrodes (3), the PL of n-ZnSe:A1 electrodes can be perturbed and EL initiated by interfacial charge-transfer processes. We show that PL quenching by applied potential is compatible with a dead-layer mode] used to describe such quenching in other PEC's (4, 5) and in Au-ZnSe Schottky diodes (6).) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114.19 Downloaded on 2015-06-07 to IP

Luminescent Properties of a Surface‐Modified Cadmium Selenide Electrode

“…We show that PL intensity from the modified electrode is in good accord with a dead-layer model found applicable to naked, homogeneous electrodes (4,7,8), and that EL properties of the modified CdSe electrode are comparable to those of the naked electrode. We show that PL intensity from the modified electrode is in good accord with a dead-layer model found applicable to naked, homogeneous electrodes (4,7,8), and that EL properties of the modified CdSe electrode are comparable to those of the naked electrode.…”

“…In this report, we examine PL and EL properties of a ferri/ferrocyanide-modified n-CdSe electrode. We show that PL intensity from the modified electrode is in good accord with a dead-layer model found applicable to naked, homogeneous electrodes (4,7,8), and that EL properties of the modified CdSe electrode are comparable to those of the naked electrode.…”

Electrochemical Luminescence of Rare Earth Metal Ion Doped MgIn[sub 2]O[sub 4] Electrodes

“…Since the 1960s, electrochemical luminescence ͑ECL͒ of semiconductors in liquid electrolyte has been intensively investigated [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and it was shown that there are two types of ECL of n-type semiconductors. 1,4,10 One is observed under cathodic polarization and its luminescence originates from the recombination of electronhole pairs with the aid of hole injection to the valence band of semiconductors by the oxidative electrolyte ͑e.g., S 2 O 8 2− or ͓Fe͑CN͒ 6 ͔ 3− ͒.…”

Luminescent Properties of Semiconductor Electrodes.

“…Although the studies described thus far have utilized edge emission, we have examined one PEC, constiucted from an n-ZnSe:Al electrode and stabilizing diselenide or ditelluride electrolyte, for which subbar Iagap P. was used for character-" ization (104). Figure 21 shows that n-ZnSe:AI ele<tu,.…”