Limiting Perovskite Solar Cell Performance by Heterogeneous Carrier Extraction

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Perovskite solar cells (PSCs) have rapidly advanced in power conversion efficiency.
• Understanding the impact of film morphology on PSC performance is crucial for further development.

Purpose of the Study:

• To investigate the effect of morphological heterogeneity in polycrystalline perovskite films on device performance using photoluminescence (PL) microscopy.
• To clarify the relationship between intra-grain properties and overall device efficiency.

Main Methods:

• Utilized photoluminescence (PL) microscopy to study polycrystalline perovskite films.
• Analyzed local carrier diffusivities and lifetimes within individual grains and across grain boundaries.
• Assessed carrier extraction efficiency at the perovskite grain-electrode interface.

Main Results:

• Local carrier diffusivities within CH3NH3PbI3 (Cl) grains are high (1.5–3.3 cm² s⁻¹), comparable to single crystals.
• Local carrier lifetimes are long (approx. 200 ns) and uniform across grains and grain boundaries.
• Significant heterogeneity in carrier extraction efficiency was observed at the perovskite grain-electrode interface.

Conclusions:

• Morphological heterogeneity does not necessarily degrade carrier lifetimes and diffusivities in perovskite films.
• The primary limitation for improved performance lies in the heterogeneity of carrier extraction at the grain-electrode interface.
• Enhancing the homogeneity of perovskite grain-electrode contacts is a promising strategy for advancing PSC technology.