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SnOx atomic layer deposition on bare perovskite - an investigation of initial growth dynamics, interface chemistry, and solar cell performance

DOI: 10.1021/acsaem.0c02405 DOI Help

Authors: Adam Hultqvist (Uppsala University) , T. Jesper Jacobsson (Uppsala University) , Sebastian Svanstrom (Uppsala University) , Marika Edoff (Uppsala University) , Ute B. Cappel (KTH Royal Institute of Technology) , Hakan Rensmo (Uppsala University) , Erik M. J. Johansson (Uppsala University) , Gerrit Boschloo (Uppsala University) , Tobias Torndahl (Uppsala University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Energy Materials

State: Published (Approved)
Published: January 2021
Diamond Proposal Number(s): 19067

Open Access Open Access

Abstract: High-end organic–inorganic lead halide perovskite semitransparent p–i–n solar cells for tandem applications use a phenyl-C61-butyric acid methyl ester (PCBM)/atomic layer deposition (ALD)-SnOx electron transport layer stack. Omitting the PCBM would be preferred for manufacturing, but has in previous studies on (FA,MA)Pb(Br,I)3 and (Cs,FA)Pb(Br,I)3 and in this study on Cs0.05FA0.79MA0.16PbBr0.51I2.49 (perovskite) led to poor solar cell performance because of a bias-dependent light-generated current. A direct ALD-SnOx exposure was therefore suggested to form a nonideal perovskite/SnOx interface that acts as a transport barrier for the light-generated current. To further investigate the interface formation during the initial ALD SnOx growth on the perovskite, the mass dynamics of monitor crystals coated by partial p–i–n solar cell stacks were recorded in situ prior to and during the ALD using a quartz crystal microbalance. Two major finds were made. A mass loss was observed prior to ALD for growth temperatures above 60 °C, suggesting the decomposition of the perovskite. In addition, a mostly irreversible mass gain was observed during the first exposure to the Sn precursor tetrakis(dimethylamino)tin(IV) that is independent of growth temperature and that disrupts the mass gain of the following 20–50 ALD cycles. The chemical environments of the buried interface were analyzed by soft and hard X-ray photoelectron spectroscopy for a sample with 50 ALD cycles of SnOx on the perovskite. Although measurements on the perovskite bulk below and the SnOx film above did not show chemical changes, additional chemical states for Pb, Br, and N as well as a decrease in the amount of I were observed in the interfacial region. From the analysis, these states and not the heating of the perovskite were concluded to be the cause of the barrier. This strongly suggests that the detrimental effects can be avoided by controlling the interfacial design.

Journal Keywords: perovskite solar cell; ALD; in situ QCM; HAXPES; interface; SnOx

Subject Areas: Materials, Chemistry, Energy

Instruments: I09-Surface and Interface Structural Analysis