Titanium-carbide MXenes for work function and interface engineering in perovskite solar cells

Abstract

To improve the efficiency of perovskite solar cells, careful device design and tailored interface engineering are needed to enhance optoelectronic properties and the charge extraction process at the selective electrodes. Here, we use two-dimensional transition metal carbides (MXene Ti3C2Tx) with various termination groups (Tx) to tune the work function (WF) of the perovskite absorber and the TiO2 electron transport layer (ETL), and to engineer the perovskite/ETL interface. Ultraviolet photoemission spectroscopy measurements and density functional theory calculations show that the addition of Ti3C2Tx to halide perovskite and TiO2 layers permits the tuning of the materials’ WFs without affecting other electronic properties. Moreover, the dipole induced by the Ti3C2Tx at the perovskite/ETL interface can be used to change the band alignment between these layers. The combined action of WF tuning and interface engineering can lead to substantial performance improvements in MXene-modified perovskite solar cells, as shown by the 26% increase of power conversion efficiency and hysteresis reduction with respect to reference cells without MXene.

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Fig. 1: Characterization of Ti3C2Tx MXene.
Fig. 2: UPS curves of pristine and MXene-doped perovskite films.
Fig. 3: DFT calculation of the MAPbI3/MXene structure.
Fig. 4: Photovoltaic parameter statistics for the investigated PSCs.
Fig. 5: Band profiles of PSCs with and without MXene as obtained by physical simulation modelling.

Data availability

The experimental data that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

The Quantum Espresso scripts for DFT calculation and TiberCad scripts for device simulations that support the findings of this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

A.D.C. and D.S. gratefully acknowledge the financial support from the Ministry of Education and Science of the Russian Federation in the framework of MegaGrant (no. 075-15-2019-872 (14.Y26.31.0027/074-02-2018-327)). A.A. and S.P. gratefully acknowledge funding from the European Union’s Horizon 2020 Research and Innovation Program (grant agreement no. 785219-GrapheneCore2).

Author information

A. Pazniak, A.D.C., D.S. and D.V.K. conceived the work. A.A. and S.P. performed the experiments on solar cells and the electro-optical characterizations. A. Pazniak produced and characterized the MXenes. A.D.V., D.R., A. Pecchia and M.A. performed the theoretical simulations. R.L. and A.L. performed UPS. A.D.C. coordinated the research activity. The manuscript was written with contributions from all the authors. All the authors approved the final version of the manuscript.

Correspondence to A. Di Carlo.

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Supplementary Figs. 1–25, Table 1, acknowledgements and Refs. 1–30.

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