Ternary Cd(Se,Te) alloy semiconductors: Synthesis, material characterization, and high-efficiency photoelectrochemical cells

Abstract

High-quality Cd(Se,Te) in two compositions were synthesized using the modified Bridgman technique. The Se-rich crystals had the hexagonal structure while the Te-rich phase consisted of crystals with cubic packing. Their quality could be gauged from the high-electron mobility and their low resistivity which suited the purpose of their synthesis, i.e., for high-efficiency photoelectrochemical cells. Photoelectrochemical etching was employed, which resulted in a heavily pitted surface with the density of the etch pits exceeding 109 cm−2. Quantum efficiency of the semiconductor/aqueous polysulfide interface increased considerably after photoetching. Solar to electrical conversion efficiencies in excess of 12% were obtained. Photoluminescence spectrum was measured for the two crystals prior to and after photoetching. The emission maximum is near the calculated band gap. The decline in the luminescence intensity, after photoetching, is attributed to the corrugation of the surface and the reduced density of the donor state near the semiconductor surface, which increases the thickness of the space-charge layer (dead layer model).

Electrical and optical properties of pulse plated CdS x Te1-x films

“…Results on pulsed laser deposited CdSTe films indicated that the films deposited below x=0.5 in CdS x Te 1-x films exhibited cubic structure, whereas films deposited at values greater than x=0.5 exhibited hexagonal structure [5]. For screen-printed CdS x Te 1-x films, films exhibited cubic structure for x<0.3 and hexagonal structure for higher values of stochiometric coefficient x [8].…”

“…The films prepared in this work possess hexagonal structure for all compositions, whereas earlier reports consist of mixed cubic and hexagonal phases. Clement et al [5] reported results on CdSeTe films with mixed hexagonal and cubic phases. Patil et al [8] also report mixed phases, and the resistivity of the films deposited by the chemical bath deposition in their work possessed high resistivities of the order of 10 4 -10 5 Ω cm, whereas the results of the present work indicate resistivities lower by four orders of magnitude.…”

“…These electrical and optical properties can suitably be tailored and tuned to the specific need in a given device structure. Among the Cd-chalcogenide group, the most prominent is the Cd-S-Te ternary alloy, the band gap of which can be tailored close to the solar energy maximum (1.4 eV) [1][2][3][4][5]. In this context, a ternary chalcogenide, especially the ternary, CdS x Te 1-x has an added advantage of tailoring the band gap to cope with the visible spectrum [6][7][8][9].…”

CdSe Photoanodes for Electrochemical Photovoltaic Conversion

“…The best results were obtained with an aqueous solution of 2.5 M Na2S, 2.5 M S and zero NaOH. The effect of electrolyte composition was studied previously [15,16].…”

(Research Award of the Energy and Technology Division) (Photo)Electrochemistry in the Service of Solar Energy Conversion

“…The semiconductors included layered compounds (MX 2 (M = Mo and W, X = S or Se, InSe, ZrSe 2 , In 2/3 PSe 3 , GeSe, etc.) [2][3][4][5][6] and II-VI alloys (such as CdTe, CdSe 1-x Te x with 0<x<1) [7][8][9]. Such study allowed to analyze the effect of the structural dimensionality of the semiconductor on the photoelectrochemical properties and to reach physical parameters of the semiconductor such as type of conductivity, bandgap, direct/indirect optical transition, Fermi level, energy positions of the band edges.…”