Femtosecond laser spectro-microscopy system

• Subject Area: Condensed Matter Physics
• Term: Funded in 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542544179

This proposal aims at the construction of a time-resolved laser-based photoluminescence microscope for the characterisation of novel semiconductors used in optoelectronic applications. An optical light microscope will be extended with a broadly tuneable laser source and a gated camera to enable detection of luminescence events resolved in time, space, and energy. A femtosecond pulsed laser with broad tuneability covering the complete spectral range from the ultraviolet to the near infrared spectral region will be used as the fundamental high-power excitation source. In such a way, the source will be usable for direct and two-photon excitation for a variety of materials with different band gaps. A pulse picker module will be employed to reduce the frequency of incoming laser pulses, where materials exhibit long-lived excited states. Appropriate beam shaping will allow for employing the excitation laser both as a tightly focused single spot light source for high-resolution confocal scanning microscopy, as well as a collimated beam with top hat profile for wide-field excitation-emission spectroscopy. Luminescence detection will be conducted with a gated camera that offers single-nanosecond to track the evolution of excited states in space (microscopy) and in energy (spectroscopy) in combination with an imaging spectrograph. Appropriate imaging optics will be changeable to switch between real-space imaging and k-space (Fourier) imaging to study the angular dispersion of optical transitions. These units will extend the capabilities of a modular set-up for correlation of multi-modal microscopy information, chiefly based on luminescence-based techniques. The system will be employed to study thin films, single crystals, and micro/nanostructures based on solution-processed semiconductors, including halide perovskites, conjugated polymers, and colloidal quantum dots. The combined time, spatial, and energy resolution will be used in concert to offer deeper insights into the fundamental photophysics of such materials, to characterise sample heterogeneity and its impact on carrier dynamics, and the pathways of sample degradation in both neat materials and extended architectures of optoelectronic devices.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Femtosekunden Laser Spektro-Mikroskopie System
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Technische Universität Chemnitz
• Leader: Dr. Simon Kahmann