Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites

Area of Science:

• Materials Science
• Optoelectronics
• Solid-State Physics

Background:

• Halide perovskites offer high performance for low-cost optoelectronic applications like photovoltaics.
• Despite high power conversion efficiencies, their performance is limited by deep trap states causing non-radiative recombination.
• The origin and distribution of these trap states, crucial for device stability and efficiency, remain largely unknown.

Purpose of the Study:

• To investigate the origin and distribution of deep trap states in halide perovskite films.
• To understand how these trap states affect charge carrier dynamics and device performance.
• To identify strategies for mitigating trap state effects and enhancing device stability.

Main Methods:

• Photoemission electron microscopy (PEEM) was used to image trap distribution at the nanoscale.
• Correlative microscopy with scanning electron analytical techniques identified trap cluster origins.
• Time-resolved photoemission spectroscopy probed photo-excited carrier trapping dynamics.

Main Results:

• Deep trap states are not uniformly distributed but form discrete, nanoscale clusters.
• These clusters are located at interfaces between crystallographically and compositionally distinct entities within the perovskite film.
• The trapping process exhibits a hole-trapping character, with kinetics limited by hole diffusion to these clusters.

Conclusions:

• The nanoscale clustering of trap states at material interfaces is a critical factor limiting halide perovskite performance.
• Controlling film microstructure and composition at the nanoscale is essential for optimizing optoelectronic devices.
• This work provides a pathway for improving the stability and efficiency of perovskite-based technologies.