Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

Abstract

The energy-band alignments for zb-ZnSe(001)/a-Zn 3 P 2 (001), w-CdS(0001)/a-Zn 3 P 2 (001), and w-ZnO(0001)/a-Zn 3 P 2 (001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and valence-band maximum for each of the bulk materials. The ZnSe/Zn 3 P 2 heterojunction had a small conduction-band offset, DE C , of À0.03 6 0.11 eV, demonstrating a nearly ideal energy-band alignment for use in thin-film photovoltaic devices. The CdS/Zn 3 P 2 heterojunction was also type-II but had a larger conduction-band offset of DE C ¼ À0.76 6 0.10 eV. A type-III alignment was observed for the ZnO/Zn 3 P 2 heterojunction, with DE C ¼ À1.61 6 0.16 eV indicating the formation of a tunnel junction at the oxide-phosphide interface. The data also provide insight into the role of the II-VI/Zn 3 P 2 band alignment in the reported performance of Zn 3 P 2 heterojunction solar cells. V C 2013 AIP Publishing LLC. [http://dx

Unravelling the early oxidation mechanism of zinc phosphide (Zn3P2) surfaces by adsorbed oxygen and water: a first-principles DFT-D3 investigation

“…The band gap is predicted at 1.51 eV in excellent agreement with experimental estimation 4 and previous DFT predictions. 17,52 It is evident from the partial density of states (PDOS) plot that the electronic states of the Zn-pd and P-p orbitals dominate the valence band, whereas the conduction band is composed of the Zn-sd orbitals.…”

“…Despite its germane optoelectronic properties, to date, a Zn 3 P 2 device of sufficient efficiency for commercial applications has not been demonstrated. [11][12][13][14][15][16] Besides problems such as poor band-alignment with buffer layers and inadequate interface passivation, 17,18 low surface stability and oxidation in the presence of oxygen [18][19][20] and moisture 21 remain major problems that severely limit the fabrication of efficient Zn 3 P 2 -based photovoltaics. Zn 3 P 2 typically reacts with moisture to form zinc hydroxide and with oxygen to form zinc phosphate.…”

Non-equilibrium alloying controls optoelectronic properties in Cu2O thin films for photovoltaic absorber applications

“…1 Examples of candidate PV materials that recently attracted a lot of attention in the scientific community include sulfides (Cu 2 ZnSnS 4 , 2 SnS, 3 Cu 2 SnS 3 , 4 Cu-Sb-S 5 ), nitrides (Cu 3 N, 6 ZnSnN 2 , 7 Cu(Ta,Nb)N 2 8 ), and phosphides (Zn 3 P 2 9 and ZnSnP 2 10 ). Oxides constitute another promising family of compounds in this regard due to their chemically robust properties, environmentally benign character and the potential for large-scale fabrication.…”

Band alignment of CBD deposited Zn(O,S)/Cu(In<inf>1&#x2212;x</inf>Ga<inf>x</inf>)Se<inf>2</inf> interface

“…al. [5]. This procedure describes using XPS core levels and valence band spectra from three surfaces -bare absorber, thick Zn(O,S) overlayer and a thin Zn(O,S) overlayer.…”