The Interplay of Contact Layers: How the Electron Transport Layer Influences Interfacial Recombination and Hole Extraction in Perovskite Solar Cells

Ilka M Hermes; Yi Hou; Victor W Bergmann; Christoph J Brabec; Stefan A L Weber

doi:10.1021/acs.jpclett.8b02824

The Interplay of Contact Layers: How the Electron Transport Layer Influences Interfacial Recombination and Hole Extraction in Perovskite Solar Cells

J Phys Chem Lett. 2018 Nov 1;9(21):6249-6256. doi: 10.1021/acs.jpclett.8b02824. Epub 2018 Oct 18.

Authors

Ilka M Hermes¹, Yi Hou², Victor W Bergmann¹, Christoph J Brabec², Stefan A L Weber^{1

3}

Affiliations

¹ Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany.
² Department of Materials Science and Engineering, Institute of Materials for Electronics and Energy Technology (i-MEET) , Friedrich-Alexander University Erlangen-Nürnberg , Martensstrasse 7 , 91058 Erlangen , Germany.
³ Institute of Physics , Johannes Gutenberg University Mainz , Duesbergweg 10-14 , 55128 Mainz , Germany.

PMID: 30256640
DOI: 10.1021/acs.jpclett.8b02824

Abstract

Charge-selective contact layers in perovskite solar cells influence the current density-voltage hysteresis, an effect related to ion migration in the perovskite. As such, fullerene-based electron transport layers (ETLs) suppress hysteresis by reducing the mobile ion concentration. However, the impact of different ETLs on the electronic properties of other constituent device layers remains unclear. In this Kelvin probe force microscopy study, we compared potential distributions of methylammonium lead iodide-based solar cells with two ETLs (planar TiO₂ and C60-functionalized self-assembled monolayer) with different hysteretic behavior. We found significant changes in the potential distribution of the organic hole transport layer spiroMeOTAD, suggesting the formation of a neutral spiroMeOTAD/iodide interface due to a reaction between iodide with p-doped spiroMeOTAD in the TiO₂ cell. Our results show that the ETL affects not only the mobile ion concentration and the recombination at the perovskite/ETL interface but also the resistance and capacitance of the spiroMeOTAD.