Single-crystal, n-type, undoped CdS and Te-doped CdS (100 and 1000 ppm CdS:Te) electrodes exhibit electroluminescence (EL) in aqueous, alkaline peroxydisulfate electrolyte. Addition of Te to CdS introduces intraband gap states which drastically alter the EL spectral distribution. The EL spectrum of undoped CdS consists of a sharp band near the band gap energy (~2.4 eV) with Xmax ~510 nm and a weaker, broader band at lower energy; the EL spectra of 100 and 1000 ppm CdS:Te also exhibit a sharp band at ~510 nm but are dominated by broad bands with uncorrected Xmax ~600 and ~620 nm, respectively. Photoluminescence (PL) spectra, obtained with 457.9-nm excitation, aid in the assignments of the emissive transitions; PL spectra are generally similar to their EL counterparts. The potential dependence of the EL spectra was examined between ~-1.2 V (onset) and -2.0 V vs. SCE, Changes in potential can affect both the relative and absolute intensities of the bands present in the EL spectra. Lower-limit, order-of-magnitude estimates of instantaneous EL efficiency, $el, have been made. Under steady-state conditions 0el is iílO-6 for undoped CdS and itlO""6 for CdS:Te. Results are discussed in terms of interfacial charge-transfer processes and the excited-state manifolds of CdS and CdS:Te.
Temperature significantly modifies the efficiencies of luminescence and photocurrent in an n‐type, single crystal,
normalCdS:normalTe‐normalbased
photoelectrochemical cell (PEC) employing aqueous polyselenide electrolyte. Between 20° and 100°C photocurrent (quantum yield
Φx
) from ultrabandgap 501.7 nm excitation increases modestly by ≲ 20%, whereas photocurrent from bandgap edge 514.5 nm excitation increases by about an order of magnitude, reaching 50–100% of the 20°C 501.7 nm photocurrent. Undoped
normalCdS
exhibits a similar photocurrent‐temperature profile. Higher temperatures thus extend the wavelength response of
normalCdS
‐ and
normalCdS:normalTe‐normalbased
PEC's. In contrast to the increase in photocurrent, emissive efficiency (quantum yield
Φr
) of
normalCdS:normalTe
drops by a factor of ∼10–20 over the same temperature range; this decline is relatively insensitive to potential and excitation wavelength (501.7 or 514.5 nm). Little change in the spectral distribution of emission
false(λmax∼600 normalnmfalse)
is observed with temperature. A dependence of emission intensity on potential is observed for the first time with 514.5 nm excitation in the high temperature regime. These results are interpreted in terms of band bending, optical penetration depth, the known red‐shift of the
normalCdS
bandgap edge with temperature, and the competitive nature of emission and photocurrent. Relationships among
Φx
,
Φr
, and
Φr0/Φr
(out‐of‐circuit to in‐circuit emission intensity) are discussed.
Die Temp. modifiziert die relativen Ausb. der Lumineszenz und des Photostroms in photoelektrochemischen Zellen auf der Grundlage von n‐leitenden, einkristallinen CdS :Te oder CdS mit wäßrigen Polyselenid‐Elektrolyten signifikant, was die konkurrierende Natur dieser beiden Deaktivierungswege für angeregte Zustände unterstreicht.
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