Field Effect Passivation in Perovskite Solar Cells by a LiF Interlayer. Issue 30 (22nd June 2022)

• Record Type: Journal Article
• Authors: Menzel, Dorothee; Al‐Ashouri, Amran; Tejada, Alvaro; Levine, Igal; Guerra, Jorge Andrés; Rech, Bernd; Albrecht, Steve; Korte, Lars
• Is Part Of: Advanced energy materials. Volume 12:Issue 30(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-22
• Subjects: C 60 -- defects -- energy level alignment -- halide perovskites -- passivation interlayers -- photoemission spectroscopy -- solar cells; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202201109
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: The fullerene C60 is commonly applied as the electron transport layer in high‐efficiency metal halide perovskite solar cells and has been found to limit their open circuit voltage. Through ultra‐sensitive near‐UV photoelectron spectroscopy in constant final state mode (CFSYS), with an unusually high probing depth of 5–10 nm, the perovskite/C60 interface energetics and defect formation is investigated. It is demonstrated how to consistently determine the energy level alignment by CFSYS and avoid misinterpretations by accounting for the measurement‐induced surface photovoltage in photoactive layer stacks. The energetic offset between the perovskite valence band maximum and the C60 HOMO‐edge is directly determined to be 0.55 eV. Furthermore, the voltage enhancement upon the incorporation of a LiF interlayer at the interface can be attributed to originate from a mild dipole effect and probably the presence of fixed charges, both reducing the hole concentration in the vicinity of the perovskite/C60 interface. This yields a field effect passivation, which overcompensates the observed enhanced defect density in the first monolayers of C60 . Abstract : Field effect passivation is identified as the origin of the voltage enhancement upon inserting a LiF interlayer at the electron selective contact of perovskite solar cells by high sensitivity near‐UV photoelectron spectroscopy. LiF increases the defect density in the C60, however, the minority charge carrier density in the vicinity of the interface is lowered, resulting in an overall reduction in the non‐radiative recombination.