Hierarchical carrier transport simulator for defected nanoparticle solids.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Renewable Energy

Background:

• Nanoparticle (NP) solar cells show high efficiency (>16%), but low carrier mobility limits performance.
• Understanding carrier transport in NP solids is crucial for advancing NP solar cell technology.
• Simulating experimental-scale NP devices is challenging due to multi-scale physical processes.

Purpose of the Study:

• To develop a multiscale simulation tool, TRIDENS, for analyzing carrier transport in defected NP solids.
• To investigate the impact of planar defects on carrier mobility in NP superlattices (SLs).
• To explore the role of percolation transitions in driving transport crossovers in NP solids.

Main Methods:

• Introduced planar defects (twin planes, grain boundaries) into NP SLs using the HINTS code.
• Simulated transport across defected NP SLs and assembled them into a resistor network (>10^7 NPs).
• Analyzed results using finite size scaling and the Efros-Shklovskii (ES) bimodal mobility distribution percolation model.

Main Results:

• TRIDENS successfully simulated transport in defected NP solids across multiple hierarchical levels.
• Planar defects were shown to significantly influence the distribution of NP SL mobilities.
• A low-mobility-to-high-mobility transport crossover, driven by percolation, was identified and characterized.

Conclusions:

• The developed TRIDENS simulator accurately models carrier transport in defected NP solids.
• The ES bimodal theory effectively characterizes the transport crossover observed in NP solids.
• Findings provide insights for optimizing NP solar cell design and improving device efficiency.