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Interfacial Modification of Perovskite Solar Cells Using an Ultrathin MAI Layer Leads to Enhanced Energy Level
Zafer Hawash1, Sonia R Raga1, Dae-Yong Son2
1Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST) , 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan.
The Journal of Physical Chemistry Letters
|August 3, 2017
Summary
Adding excess methylammonium iodide (MAI) to perovskite solar cells (PSCs) tunes interface energy levels. This optimization boosts power conversion efficiency (PCE) and improves device reproducibility.
Area of Science:
- Materials Science
- Renewable Energy
- Photovoltaics
Background:
- Perovskite solar cells (PSCs) are a promising photovoltaic technology.
- Interface engineering is crucial for optimizing PSC performance and stability.
- Methylammonium lead iodide (MAPI) is a common perovskite absorber material.
Purpose of the Study:
- To investigate the effect of excess methylammonium iodide (MAI) on the MAPI perovskite film interface.
- To understand the role of MAI in tuning the energy levels at the perovskite/hole-transport layer interface.
- To improve the power conversion efficiency (PCE) and reproducibility of PSCs.
Main Methods:
- Intentional deposition of ultrathin excess MAI layers on MAPI films.
- Photoelectron spectroscopy (X-ray photoelectron spectroscopy - XPS) to analyze interfacial composition and electronic properties.
- Fabrication and testing of standard structure PSC devices.
Main Results:
- Excess MAI, particularly dissociated species at low thicknesses (<16 nm), favorably tunes the MAPI film's interfacial energy levels.
- Optimized interface energetics led to a 19% increase in average steady-state power conversion efficiency (PCE).
- Significant improvement in device reproducibility was observed, with PCE standard deviation decreasing from 15 ± 2% to 17.2 ± 0.4%.
Conclusions:
- The intentional use of excess MAI is an effective strategy for interfacial energy-level tuning in MAPI-based PSCs.
- Dissociated MAI species, not the intact layer, are responsible for the observed energetic modifications.
- This interface engineering approach enhances both the efficiency and reproducibility of perovskite solar cells.
