Chemical and electronic structure of the heavily intermixed Cd,Zn S Ga CuSbS2 interface

The interface formation and chemical and electronic structure of the Cd,Zn S Ga CuSbS2 thin film solar cell heterojunction were studied using hard X ray photoelectron spectroscopy HAXPES of the bare absorber and a buffer absorber sample set for which the buffer thickness was varied between 1 and 50 nm. We find a heavily intermixed interface, involving Cu, Zn, and Cd as well as significant Ga and Cu profiles in the buffer. The valence band VB offset at the buffer absorber interface was derived as amp; 8722;1.3 0.1 eV, which must be considered an upper bound as the Cu diffused into the buffer might form a Cu derived VB maximum located closer to the Fermi level. The estimated conduction band minimum was cliff like; a situation made more severe considering the Cu deficiency found for the CuSbS2 surface. The complex interface structure s effect on the performance of Cd,Zn S Ga CuSbS2 based solar cells and its limitation is discussed together with possible mitigation strategie

Photoinduced phase segregation and degradation of perovskites revealed by x ray photoelectron spectroscopy

Pb based Pperovskite absorbers based withon organic i.e., CH3NH3 and inorganic i.e., Cs cations with and a halide composition of 75 Br and 25 I are investigated with x ray photoelectron spectroscopy while submitted to environmental stress factors to study their stability. Changes in chemical properties of the absorbers were monitored in ultra high vacuum and under simulated solar, as well as, x ray irradiation. Although changes are detected for both types of perovskite absorbers, the organic cation perovskite exhibits a more pronounced tendency to photodegrad

Observation and Mediation of the Presence of Metallic Lead in Organic Inorganic Perovskite Films

We have employed soft and hard X-ray photoelectron spectroscopies to study the depth-dependent chemical composition of mixed-halide perovskite thin films used in high-performance solar cells. We detect substantial amounts of metallic lead in the perovskite films, which correlate with significant density of states above the valence band maximum. The metallic lead content is higher in the bulk of the perovskite films than at the surface. Using an optimized postanneal process in air, we can reduce the metallic lead content in the perovskite film. This process reduces the amount of metallic lead and a corresponding increase in the photoluminescence quantum efficiency of the perovskite films can be observed. This correlation indicates that metallic lead impurities are likely a key defect whose concentration can be controlled by simple annealing procedures in order to increase the performance for perovskite solar cells

Photoinduced phase segregation and degradation of perovskites revealed by x-ray photoelectron spectroscopy

Pb-based perovskite absorbers with organic (i.e., CH3NH3+) and inorganic (i.e., Cs+) cations and a halide composition of 75% Br and 25% I are investigated with x-ray photoelectron spectroscopy while submitted to environmental stress factors to study their stability. Changes in chemical properties of the absorbers were monitored in ultra-high vacuum and under simulated solar, as well as, x-ray irradiation. Although changes are detected for both types of perovskite absorbers, the organic cation perovskite exhibits a more pronounced tendency to photodegrade

Direct observation of an inhomogeneous chlorine distribution in CH3NH3PbI3 xClx layers surface depletion and interface enrichment

X-ray spectroscopies have shown a higher chlorine concentration near the perovskite/TiO2 interface than throughout the rest of the perovskite film.</p

Dynamic Effects and Hydrogen Bonding in Mixed-Halide Perovskite Solar Cell Absorbers

The organic component (methylammonium) of CH3NH3PbI3–xClx-based perovskites shows electronic hybridization with the inorganic framework via H-bonding between N and I sites. Femtosecond dynamics induced by core excitation are shown to strongly influence the measured X-ray emission spectra and the resonant inelastic soft X-ray scattering of the organic components. The N K core excitation leads to a greatly increased N–H bond length that modifies and strengthens the interaction with the inorganic framework compared to that in the ground state. The study indicates that excited-state dynamics must be accounted for in spectroscopic studies of this perovskite solar cell material, and the organic–inorganic hybridization interaction suggests new avenues for probing the electronic structure of this class of materials. It is incidentally shown that beam damage to the methylamine component can be avoided by moving the sample under the soft X-ray beam to minimize exposure and that this procedure is necessary to prevent the creation of experimental artifacts