Solution-processed p-type nanocrystalline CoO films for inverted mixed perovskite solar cells

Bin Li; Yichuan Rui; Jingli Xu; Yuanqiang Wang; Jingxia Yang; Qinghong Zhang; Peter Müller-Buschbaum

doi:10.1016/j.jcis.2020.03.119

Solution-processed p-type nanocrystalline CoO films for inverted mixed perovskite solar cells

J Colloid Interface Sci. 2020 Aug 1:573:78-86. doi: 10.1016/j.jcis.2020.03.119. Epub 2020 Mar 30.

Authors

Bin Li¹, Yichuan Rui², Jingli Xu¹, Yuanqiang Wang¹, Jingxia Yang¹, Qinghong Zhang³, Peter Müller-Buschbaum⁴

Affiliations

¹ College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, PR China.
² College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, PR China. Electronic address: ryc713@126.com.
³ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, PR China.
⁴ Lehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, Jams-Franck-Strasse 1, 85748 Garching, Germany; Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, 85748 Garching, Germany. Electronic address: muellerb@ph.tum.de.

PMID: 32259694
DOI: 10.1016/j.jcis.2020.03.119

Abstract

Inorganic p-type materials show great potential as the hole transport layer in perovskite solar cells with the merits of low costs and enhanced chemical stability. As a p-type material, cobalt oxide (CoO) has received so far not that level of attention despite its high hole mobility. Herein, solution-processed p-type CoO nanocrystalline films are developed for inverted mixed perovskite solar cells. The ultrafine CoO nanocrystals are synthesized via an oil phase method, which are subsequently treated by a ligand exchange process using pyridine solvent to remove the long alkyl chains covering the nanocrystals. From this homogeneous colloidal solution CoO films are obtained, which exhibit a smooth and pin-hole free surface morphology with high transparency and good conductivity. The ultraviolet photoelectron spectrum also indicates that the energy levels of the CoO film match well with the mixed perovskite Cs_0.05(FA_0.83MA_0.17)_0.95(I_0.83Br_0.17)₃. Inverted solar cells based on crystalline CoO films with ligand exchange show a reasonable energy conversion efficiency, whereas devices based on CoO films without ligand exchange suffer from a strong S-shape JV-characteristic. Thus, the crystalline CoO films are foreseen to pave a new way of inorganic hole transport materials in the fields of perovskite solar cells.

Keywords: Cobalt oxide; Colloids; Hole transport layers; Perovskite solar cells; p-type.