Organic-inorganic halide perovskites incorporating two-dimensional (2D) structures have shown promise for enhancing the stability of perovskite solar cells (PSCs). However, the bulky spacer cations often limit charge transport. Here, we report on a simple approach based on molecular design of the organic spacer to improve the transport properties of 2D perovskites, and we use phenethylammonium (PEA) as an example. We demonstrate that by fluorine substitution on the para position in PEA to form 4-fluorophenethylammonium (F-PEA), the average phenyl ring centroid-centroid distances in the organic layer become shorter with better aligned stacking of perovskite sheets. The impact is enhanced orbital interactions and charge transport across adjacent inorganic layers as well as increased carrier lifetime and reduced trap density. Using a simple perovskite deposition at room temperature without using any additives, we obtained a power conversion efficiency of >13% for (F-PEA)2MA4Pb5I16-based PSCs. In addition, the thermal stability of 2D PSCs based on F-PEA is significantly enhanced compared to those based on PEA.
Bibliographical noteFunding Information:
The work was supported by the U.S. Department of Energy under Contract No. DE-AC36-08GO28308 with Alliance for Sustainable Energy, Limited Liability Company (LLC), the Manager and Operator of the National Renewable Energy Laboratory. We acknowledge the support of perovskite synthesis and device fabrication/characterization, and microwave cavity modeling and characterization from the Derisking Halide Perovskite Solar Cells program of the National Center for Photovoltaics, funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Solar Energy Technologies Office; the support of the in-plane and out-of-plane transport measurement and analysis from the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science within the U.S. Department of Energy; and the support of density functional theory calculations by supercomputer time awarded through PRACE on the Swiss National Supercomputing Centre (CSCS) under project pr51. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government.
Copyright © 2019 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry