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The Electronic Structure of MAPI‐Based Perovskite Solar Cells: Detailed Band Diagram Determination by Photoemission Spectroscopy Comparing Classical and Inverted Device Stacks
Author(s) -
Hellmann Tim,
Das Chittaranjan,
Abzieher Tobias,
Schwenzer Jonas A.,
Wussler Michael,
Dachauer Ralph,
Paetzold Ulrich W.,
Jaegermann Wolfram,
Mayer Thomas
Publication year - 2020
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.202002129
Subject(s) - materials science , band diagram , perovskite (structure) , non blocking i/o , optoelectronics , surface photovoltage , x ray photoelectron spectroscopy , energy conversion efficiency , vacuum deposition , layer (electronics) , spectroscopy , deposition (geology) , nanotechnology , chemical engineering , heterojunction , catalysis , paleontology , biochemistry , chemistry , physics , quantum mechanics , sediment , engineering , biology
High power conversion efficiency (PCE) perovskite solar cells (PSCs) rely on optimal alignment of the energy bands between the perovskite absorber and the adjacent charge extraction layers. However, since most of the materials and devices of high performance are prepared by solution‐based techniques, a deposition of films with thicknesses of a few nanometers and therefore a detailed analysis of surface and interface properties remains difficult. To identify the respective photoactive interfaces, photoelectron spectroscopy measurements are performed on device stacks of methylammonium‐lead‐iodide (MAPI)‐based PSCs in classical and inverted architectures in the dark and under illumination at open‐circuit conditions. The analysis shows that vacuum‐deposited MAPI perovskite absorber layers are n‐type, independent of the architecture and of the charge transport layer that it is deposited on (n‐type SnO 2 or p‐type NiO x ). It is found that the majority of the photovoltage is formed at the n‐MAPI/p‐HEL (hole extraction layer) junction for both architectures, highlighting the importance of this interface for further improvement of the photovoltage and therefore also the PCE. Finally, an experimentally derived band diagram of the completed devices for the dark and the illuminated case is presented.