Investigating the relationship between the atomic or molecular structure of materials and their macroscopic properties is a core aspect in the interdisciplinary field of materials science. The insights thus gained help in creating or modifying materials for improved performance. PicoQuant provides powerful tools like steady-state and time-resolved spectroscopy or microscopy to study a material’s excited state dynamics and processes. Coupling our fluorescence microscopes and spectrometers enables the acquisition of steady-state and time-resolved spectra from defined points or regions of interest in the sample. The resulting multidimensional datasets provide valuable new insights. Several combinations of different instruments are possible. Depending on the research question, one may be more suitable than others.
Studied with TRPL Imaging and Carrier Diffusion Mapping
Investigations of solar cells, photovoltaic devices, and semiconductors are essential to enhance their electronic and optical properties as well as the efficiency of their preparation methods. We present a powerful toolbox of non-destructive time-resolved spectroscopy and microscopy techniques for researchers. The combination of these two techniques enables investigations of photophysical properties of semiconductors on a whole new level.
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Quantum Well Wafer Dynamics in Optoelectronics and Semiconductor Devices
A quantum well wafer is a specialized semiconductor structure used in the fields of optoelectronics and semiconductor devices. It consists of a thin layer of a semiconductor material, in this case GaAsP, sandwiched between two thicker layers of a different semiconductor material, in this case AlGaAs. The key feature of the quantum well layer is that it's thickness of a few nanometers confines the motion of electrons in one dimension, which leads to quantized energy levels that result in several unique properties. These enable for example creation of lasers with specific wavelengths or enhancement of photodetector efficiency. The motion of free electrons, i.e. the charge carrier dynamics, can be observed with TRPL measurements.
We thank Andrea Knigge from the Ferdinand-Braun Institute in Berlin, Germany for the quantum well sample.
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Lighting and Display Device Technologies
LED (Light-Emitting Diode) materials are essential components in lighting and display device technologies, and understanding their properties is crucial for optimizing performance. This includes advanced technologies such as OLEDs, QLEDs, µLEDs, nanoLEDs, and perovskite LEDs (PeLEDs). Time-resolved microscopy and spectroscopy are valuable tools for the characterization of new LED materials. From time-resolved data, researchers can elucidate charge carrier dynamics, including carrier trapping, diffusion, and recombination. For example, shorter lifetimes may indicate non-radiative recombination pathways that reduce the LED's efficiency. Thus, understanding these dynamics is crucial for optimizing LED materials and manufacturing processes to reduce non-radiative losses.
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Singlet Oxygen Detection, CO2 Photoreduction, H2 Production, and Environmental Purification
Photocatalysis is a process that utilizes the energy of light to activate a substance, known as a photocatalyst, to drive chemical reactions. It has a wide range of applications, including environmental purification, and chemical synthesis. The photocatalyst typically is a semiconducting material like titanium dioxide or zinc oxide. When the photocatalyst is exposed to light, electrons in the material are excited from the valence band to the conduction band, creating electron-hole pairs. These charge carriers are essential for driving chemical reactions.
Improving the efficiency and selectivity of photocatalysts is essential to maximize their performance in various applications. Ongoing research in this field pursues various strategies, such as sensitization, enhancing charge separation, or improving light utilization.
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Quantum Dots, Carbon Dots, TMDs
Nanomaterials, including nanoparticles and 2D materials, are unique due to their remarkable physical, chemical, and electronic properties that emerge at the nanoscale because of quantum confinement. For example, they can scatter, absorb, or emit light differently from bulk materials. 2D materials like graphene have excellent electron transport properties, making them attractive for next-generation electronic devices and transparent conductive films.
The properties of nanomaterials can be finely tuned by adjusting their size, shape, or composition. This tunability is essential for tailoring them to specific applications, from electronics to catalysis. Working with nanomaterials also presents challenges, and TRPL is one of the characterization techniques that can address these challenges.
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Advanced Material Characterization
Time-Resolved Photoluminescence (TRPL) is a powerful technique for investigating the optical and electronic properties of materials by measuring photoluminescence decay times following pulsed excitation. This method enables precise analysis of fluorescence lifetimes, which typically span from picoseconds to milliseconds, depending on the material and its environment.
TRPL reveals key insights into processes such as charge carrier dynamics, defect states, and local emission behavior, making it indispensable in the characterization of nanomaterials and 2D materials such as quantum dots and transition metal dichalcogenides (TMDs).
As a key tool in materials science, TRPL plays a central role in optimizing next-generation technologies – including semiconductor characterization, solar cell research and LED characterization.
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Uncover Hidden Dynamics in Advanced Materials
Time-resolved photoluminescence (TRPL) imaging, a spatially resolved extension of the broader TRPL technique, is a powerful, non-invasive technique that maps photoluminescence lifetimes with spatial resolution – offering detailed insight into dynamic processes such as carrier diffusion, defect distribution, and local inhomogeneities across a wide range of materials.
Its versatility makes TRPL imaging especially valuable in materials science applications such as semiconductor characterization, solar cell research, LED characterization and research of nanoparticles and 2D materials, supporting both cutting-edge research and real-world device optimization.
The image on the right illustrates how TRPL imaging can distinguish local variations in photoluminescence lifetimes and intensities, helping to identify defects and heterogeneities at the microscale – an essential step in evaluating material performance.
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Identifying single photon emitters
Antibunching is a characteristic of light with sub-Poissonian statistics. Observation of antibunching (by means of photon coincidence correlation or second-order correlation) for instance reveals whether there is only a single photon emitter present in a sample. The technique is very often employed in the characterization of single quantum systems such as single molecules, quantum dots, carbon nanotubes, and defect centers in diamond nanocrystals, or in applications based on single photons sources. Antibunching experiments can also reveal the degree of multimerization
of fluorophores.
The antibunching dip of the correlation function is based on the fact that a single emitter can only emit one photon at a time. The process can easily be described using a simplified two-level energy diagram, where a molecule in an excited state requires a finite amount of time before it relaxes back to the ground state by emitting a photon. The temporal separation between adjacent photons is therefore determined mostly by the excited-state lifetime. This effect is known as antibunching and represents the sub-Poissonian nature of the emitted light.
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