Defects controlling electrical and optical properties of electrodeposited Bi doped Cu2O

Abstract

Doping leading to low electrical resistivity in electrodeposited thin films of Cu 2 O is a straightforward requirement for the construction of efficient electronic and energy devices. Here, Bi (7 at. %) doped Cu 2 O layers were deposited electrochemically onto Si(100) single-crystal substrates from aqueous solutions containing bismuth nitrate and cupric sulfate. X-ray photoelectron spectroscopy shows that Bi ions in a Cu 2 O lattice have an oxidation valence of 3þ and glancing angle X-ray diffraction measurements indicated no presence of secondary phases. The reduction in the electrical resistivity from undoped to Bi-doped Cu 2 O is of 4 and 2 orders of magnitude for electrical measurements at 230 and 300 K, respectively. From variations in the lattice parameter and the refractive index, the electrical resistivity decrease is addressed to an increase in the density of Cu vacancies. Density functional theory (DFT) calculations supported the experimental findings. The DFT results showed that in a 6% Bi doped Cu 2 O cell, the formation of Cu vacancies is more favorable than in an undoped Cu 2 O one. Moreover, from DFT data was observed that there is an increase (decrease) of the Cu 2 O band gap (activation energy) for 6% Bi doping, which is consistent with the experimental results.

Influence of Strain on the Band Gap of Cu2O

“…21,22 A possibility to tune the band gap in oxides is the addition of dopants. 21,23 Upon doping, the band gap is affected by two parameters, the dopant size 24 and the interactions between the electronic structure of the dopant and Cu 2 O. 25,26 Differences in the ion size are thought to introduce structural modifications in the Cu 2 O network which in turn modifies the Cu-Cu interactions.…”

“…All these applications have the requirement of suitable band gaps in common. For example, in the case of transparent conducting oxides a large band gap is required to avoid absorption of visible light. , For photoelectrochemical water splitting, on the other hand, the band gap should be close to 1.6 eV to maximize the use of the solar spectrum. , A possibility to tune the band gap in oxides is the addition of dopants. , Upon doping, the band gap is affected by two parameters, the dopant size and the interactions between the electronic structure of the dopant and Cu 2 O. , Differences in the ion size are thought to introduce structural modifications in the Cu 2 O network which in turn modifies the Cu–Cu interactions . These interactions have been reported to dominate the CB or VB. , In the case of a dopant smaller than Cu + , the band gap is narrowed while it becomes wider upon addition of larger ions. , Interactions between the electronic structure of Cu 2 O and the dopant on the other hand can result in the appearance of interband states − or in the case of inert ions in the disturbance of the Cu–Cu interactions …”

Opportunities from Doping of Non‐Critical Metal Oxides in Last Generation Light‐Conversion Devices

“…[215] Unlike previous examples, Cu 2 O doping has been rarely employed as a strategy to improve the PEC performance due to the limited enhancement observed in the few attempts reported. Indeed, the carrier concentration improvement observed by doping with transition metals such as Bi, [157] Zn, [158] and Ni [159] did not result in a significant improvement of Cu 2 O photocathodes. On the other hand, doping with halogens like Cl, [160] often unintentionally introduced in Cu 2 O lattice, [216] might result in undesired n-type characteristics.…”

Strain or Electronic Effects? – The influence of alkali metals on the bandgap of Cu2O

“…Cuprous oxide is an intrinsic p-type semiconductor with a bandgap of 2.17 eV [1,2] which renders it a promising material for transparent semiconductors [3][4][5] or photocathodes in water splitting. [1,[6][7][8][9][10][11][12] A possibility to tune the band-gap and thus, the performance of cuprous oxide is the addition of dopants. [4][5][6][7][8] 16] The increased or decreased bandgap can be associated mainly with two effects, the differences in ionic radii (geometric effects) and the direct changes to the electronic structure induced by dopants (electronic effects).…”

“…[1,[6][7][8][9][10][11][12] A possibility to tune the band-gap and thus, the performance of cuprous oxide is the addition of dopants. [4][5][6][7][8] 16] The increased or decreased bandgap can be associated mainly with two effects, the differences in ionic radii (geometric effects) and the direct changes to the electronic structure induced by dopants (electronic effects). Since typically both effects are present it is difficult to distinguish them in traditional studies [3,6,8,9,13,17] which simply consider the influence of dopants within Cu 2 O.…”