Pure 2D Perovskite Formation by Interfacial Engineering Yields a High Open-Circuit Voltage beyond 1.28 V for 1.77-eV...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Wide-bandgap perovskite solar cells (PSCs) show promise but suffer from open-circuit voltage (V_OC) losses.
• Current surface post-treatments, like ammonium halides, reduce V_OC losses but lack mechanistic understanding.
• Device efficiency in these PSCs remains suboptimal compared to their potential.

Purpose of the Study:

• To investigate a facile strategy for tailoring 2D perovskite phase purity on 3D wide-bandgap (WBG) perovskite layers.
• To understand the mechanism of defect passivation and surface electric-field formation.
• To achieve high power conversion efficiency (PCE) in WBG PSCs.

Main Methods:

• Fabrication of 3D WBG perovskite solar cells with a tailored 2D perovskite layer.
• Low-temperature annealing to form pure n=1 2D perovskites.
• Utilized transient absorption spectra, cross-sectional confocal photoluminescence mapping, and Kelvin probe force microscopy for analysis.

Main Results:

• Achieved optimal defect passivation and a favorable surface electric-field with pure n=1 2D perovskites on 3D WBG perovskites.
• An inverted champion device with a 1.77-eV bandgap absorber reached a V_OC of 1.284 V and a PCE of 17.72%.
• Reported the smallest V_OC deficit (0.486 V) for WBG PSCs with bandgaps >1.75 eV.

Conclusions:

• The precise tailoring of 2D perovskite layers offers an effective strategy for enhancing WBG PSC performance.
• This approach significantly reduces V_OC deficit, paving the way for highly efficient devices.
• Enabled the development of a four-terminal all-perovskite tandem solar cell with a PCE exceeding 25%.