In-gap states in titanium dioxide and oxynitride atomic layer deposited films

Abstract

Valence band (VB) spectra of titanium dioxide (TiO2) and oxynitride (TiOxNy) films prepared by different atomic layer deposition (ALD) processes are compared and related to electrical characterization [current–voltage (JV) and capacitance–voltage (CV)] results. By increasing the nitrogen amount in the TiO2 film, band-gap narrowing is observed. The band-gap decrease is related to the contribution of the nitrogen density of states, which induces defects within the band-gap and thus reduces its optical band-gap. In-gap states are found in the VB spectra at 1 eV below the Fermi energy in all investigated ALD samples, i.e., in TiO2 as well as in TiOxNy films. An exponential correlation between leakage current density and in-gap state intensity is derived by the combination of JV measurements and VB spectra, whereas the in-gap states seem to have no influence on hysteresis and fixed oxide charges found in the CV data. It is argued that the in-gap states in TiO2 and TiOxNy have an excitonic or polaronic origin. Both, band-gap narrowing and in-gap state intensity can be tuned by the ALD process selection and the variation of its parameters.

Top‐Down Approach to Study Chemical and Electronic Properties of Perovskite Solar Cells: Sputtered Depth Profiling Versus Tapered Cross‐Sectional Photoelectron Spectroscopies

“…The Ti2p 3/2 core level is very sharp and is located at 459.8 eV corresponding to the binding energy of TiO 2 . [ 50,51 ] The O1s has two peaks located at 530.0 and 532.6 eV. The higher binding energy (532.6 eV) peak is found all over the TCS profile, whereas the lower binding energy peak appears at around point 15 along with the Ti2p.…”

“…The electronic properties at the interfaces [ 49,50 ] are the factors responsible for the performance of the photovoltaic devices. [ 51,52 ] These factors are intimately related to the changes in the chemistry of the layers at the interfaces, which can be determined with PES. [ 53–55 ] In Figure a,c, C1s and Pb4f 7/2 core‐level spectra are presented that were collected at the Ag surface, the spiro‐MeOTAD/perovskite interface, and in the middle of the perovskite layer using SDP‐PES.…”

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Characterization of Electronic Transport through Amorphous TiO2 Produced by Atomic Layer Deposition

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The chemistry and energetics of the interface between metal halide perovskite and atomic layer deposited metal oxides

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