Revisiting the properties of delafossite CuCrO2: A single crystal study

Critical Review of Cu-Based Hole Transport Materials for Perovskite Solar Cells: From Theoretical Insights to Experimental Validation

Despite the remarkable efficiency of perovskite solar cells (PSCs), long-term stability remains the primary barrier to their commercialization. The prospect of enhancing stability by substituting organic transport layers with suitable inorganic compounds, particularly Cu-based inorganic hole-transport materials (HTMs), holds promise due to their high valence band maximum (VBM) aligning with perovskite characteristics. This review assesses the advantages and disadvantages of these five types of Cu-based HTMs. Although Cu-based binary oxides and chalcogenides face narrow bandgap issues, the "chemical modulation of the valence band" (CMVB) strategy has successfully broadened the bandgap for Cu-based ternary oxides and chalcogenides. However, Cu-based ternary oxides encounter challenges with low mobility, and Cu-based ternary chalcogenides face mismatches in VBM alignment with perovskites. Cu-based binary halides, especially CuI, exhibit excellent properties such as wider bandgap, high mobility, and defect tolerance, but their stability remains a concern. These limitations of single anion compounds are insightfully discussed, offering solutions from the perspective of practical application. Future research can focus on Cu-based composite anion compounds, which merge the advantages of single anion compounds. Additionally, mixed-cation chalcogenides such as CuxM1-xS enable the customization of HTM properties by selecting and adjusting the proportions of cation M.

Improving the p-Type CuCrO2 Thin Film's Electrical and Optical Properties

In this research, we studied the functional properties of CuCrO₂, which is the most promising p-type transparent conductive oxide (TCO). The thin films were fabricated using a spin coating technique. The diffraction patterns were obtained with the help of X-ray diffractions, and the optical properties of absorption characteristics were studied using UV-visible absorption. The physical properties of film formation and surface morphology were analyzed using FESEM analysis. The aging properties were also analyzed with the help of various precursors with different aging times. The CuCrO₂ thin films' functional properties were determined by using chelating agent and precursor solution aging times. The CuCrO₂ thin films have better transmittance, resistance, figure of merit (FOM), and electrical conductivity. Moreover, the resistivity values of the CuCrO₂ thin films are 7.01, 9.90, 12.54, 4.10, 2.42, and 0.35 Ω cm. The current research article covers the preparation of copper chromium delafossite thin films. These thin films can be suitable for hole transport layers in transparent optoelectronic devices.

The Optoelectronic Properties of p-Type Cr-Deficient Cu[Cr0.95-xMg0.05]O2 Films Deposited by Reactive Magnetron Sputtering

CuCrO₂ is one of the most promising p-type transparent conductive oxide (TCO) materials. Its electrical properties can be considerably improved by Mg doping. In this work, Cr-deficient CuCrO₂ thin films were deposited by reactive magnetron sputtering based on 5 at.% Mg doping. The influence of Cr deficiency on the film's optoelectronic properties was investigated. As the film's composition varied, CuO impurity phases appeared in the film. The mixed valency of Cu⁺/Cu²⁺ led to an enhancement of the hybridization between the Cu3d and O2p orbitals, which further reduced the localization of the holes by oxygen. As a result, the carrier concentration significantly improved. However, since the impurity phase of CuO introduced more grain boundaries in Cu[Cr_0.95-xMg_0.05]O₂, impeding the transport of the carrier and incident light in the film, the carrier mobility and the film's transmittance reduced accordingly. In this work, the optimal optoelectronic performance is realized where the film's composition is Cu[Cr_0.78Mg_0.05]O₂. Its Haacke's figure of merit is about 1.23 × 10^-7 Ω^-1.

Crystallite size dependence of thermoelectric performance of CuCrO2

The thermoelectric performance of CuCrO₂ with different particle size and morphology is influenced more by electrical resistivity than thermal conductivity.

A detailed study of the magnetic phase transition in CuCrO2

The phase transition in CuCrO2 to an ordered magnetic state is studied with bulk measurements and elastic and inelastic neutron scattering techniques. The reported onset of spontaneous electric polarization at T = 23.5 K coincides with the appearance, on cooling, of elastic magnetic scattering. At higher temperatures long range magnetic correlations gradually develop but they are dynamic. The ground state is characterized by three-dimensional long range magnetic ordering but along the c direction the correlation length remains limited to ∼200 Å.