Reliable Electronic Trap Characterization in Metal Halide Perovskites via Advanced Photophysical Techniques

• Applicant: Dr. Chris Dreessen
• Subject Area: Experimental Condensed Matter Physics ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576639778

Halide perovskite solar cells are among the most promising next-generation photovoltaic technologies, both as stand-alone devices and in tandems with established silicon cells. Their combination of exceptional optoelectronic quality and low-temperature fabrication is remarkable, since other semiconductors require energy-intensive processes to achieve the defect-free crystal quality needed for electronic applications. This raises a key scientific question: how can perovskites perform so well despite being produced under conditions that typically lead to many crystallographic defects? Such defects often create electronic “traps” within the material’s bandgap, where charge carriers recombine instead of contributing to electrical power. Trap-related recombination can be fully described by three types of parameters which together form a fingerprint of the defect: trap density, energetic position, and capture rates for electrons and holes. In practice, however, determining these parameters reliably in perovskites remains a major challenge. Their low doping density and high ionic mobility make conventional characterization methods prone to artifacts, and no established protocol currently exists that can unambiguously resolve all trap parameters. This project will close this gap by developing the first comprehensive, experimentally validated measurement protocol for perovskite trap characterization. It builds on our prior work demonstrating that high dynamic range in time-resolved photoluminescence (TRPL) and steady-state photoluminescence (ssPL) is essential for modeling recombination dynamics. The approach will adapt and integrate three recent methods for trap characterization in perovskites: (1) TRPL-ssPL, (2) multipulse TRPL, and (3) photo-Hall measurements. Multipulse TRPL uses patterns of laser pulses to probe both steady-state and transient recombination dynamics, enabling determination of carrier densities and trap parameters directly. Photo-Hall measurements complement this by providing polarity-dependent carrier concentration and lifetime. Applying all three techniques to the same films will establish a complete, cross-validated picture of recombination processes, identify the trap model that best describes perovskites, and determine the origin of their exceptional optoelectronic quality. Finally, by deliberately altering the film stoichiometry, I will link these electronic fingerprints to their chemical origins, enabling defect-targeted strategies for higher efficiency and stability. The project will therefore enable systematic tracking of technological improvements, link the electronic parameters to specific chemical defects for targeted optimization, shed light on the causes of instability, and reveal why perovskites achieve such high performance, guiding the search for other low-cost, high-quality materials.

• DFG Programme: Research Grants