Time-Resolved Emission Spectroscopy (TRES)

Time-Resolved Spectral Analysis of Emission

A time-resolved spectroscopy technique that records emission spectra as a function of time to resolve excited-state dynamics and spectral evolution in materials.
Three-dimensional representation of time-resolved emission spectra of tryptophan in saline buffer. Thirty-one wavelength-resolved decay curves were recorded and globally analyzed, revealing three characteristic lifetimes of 360 ps, 2.5 ns, and 7.4 ns.
Table of contents

Revealing Emission Dynamics Across Time and Wavelength

What is TRES?

Time-Resolved Emission Spectroscopy (TRES) is a optical spectroscopy technique that records emission spectra as a function of time after pulsed excitation. Instead of measuring a single fluorescence decay at a fixed wavelength, TRES captures the full spectral evolution of an emitting system, revealing how emission intensity and spectral shape change during excited-state relaxation. This approach reveals how emission intensity and spectral position evolve during relaxation of excited states, giving insight into dynamic molecular processes such as carrier relaxation, defect-related emission, exciton localization, and environmental effects in functional materials and nanostructures.

Time-resolved emission spectra reconstructed from global analysis of wavelength-resolved decay data. The spectral components correspond to three distinct lifetimes of 360 ps, 2.5 ns, and 7.4 ns, illustrating excited-state heterogeneity in the sample.Time-resolved emission spectra reconstructed from global analysis of wavelength-resolved decay data. The spectral components correspond to three distinct lifetimes of 360 ps, 2.5 ns, and 7.4 ns, illustrating excited-state heterogeneity in the sample.

How does TRES work?

In TRES, a sample is excited using short laser or LED pulses, and the emitted photons are detected with both temporal and spectral resolution. Emission is dispersed by a spectrometer, and time-resolved detection is performed for multiple wavelength channels, typically using TCSPC electronics. For each wavelength, a fluorescence decay is recorded relative to the excitation pulse. By assembling these decays, researchers obtain a complete time-dependent emission spectrum that shows how spectral features shift and intensities vary during relaxation.

EasyTau 2 interface for fluorescence lifetime data analysisEasyTau 2: spectroscopy control and analysis software

TRES Data & Analysis

TRES data consist of wavelength-resolved fluorescence decay curves that can be visualized as time-resolved emission spectra or three-dimensional intensity maps as a function of wavelength and time. Analysis commonly involves global fitting methods that evaluate several decay traces simultaneously to extract common lifetimes and wavelength-dependent amplitudes. This approach helps to separate overlapping emissive species and reveals dynamic spectral evolution associated with excited-state processes, environmental relaxation, or kinetic transitions between different molecular states.

PicoQuant software for TRPL analysis

PicoQuant’s EasyTau 2 software enables intuitive TRES data acquisition and decay analysis in a single streamlined workflow.

 

Why use TRES?

TRES enables direct investigation of time-dependent emission processes in functional and optoelectronic materials. It allows researchers to resolve carrier relaxation pathways, distinguish defect-related and band-edge emission, and track spectral shifts associated with exciton trapping, charge transfer, or structural disorder. By combining spectral and temporal information, TRES provides a deeper understanding of recombination mechanisms in semiconductors, nanomaterials, and thin films, supporting the optimization of material performance for photonic and energy-related applications.

FluoTime 300 photoluminescence spectrometer for steady-state and time-resolved measurementsFluoTime 300 - high-end photoluminescence spectrometer.

Instrumentation requirements for TRES

Accurate TRES experiments require short-pulse excitation sources, spectrally resolving detection optics, and time-resolved photon counting electronics. Typical setups include pulsed lasers or LEDs, spectrometers with multi-channel detection, and sensitive photon-counting devices connected to TCSPC systems capable of handling multiple wavelength channels. The instrumentation must provide stable synchronization between excitation and detection. Integrated control and analysis software is essential for automated acquisition, synchronization of spectral and temporal data, and efficient global analysis of time-resolved emission data.

Relevant for Your Research​

Matching Applications

Schematic illustration of nanostructured materials on a substrate, highlighting heterogeneous nanoscale architectures relevant for optical and time-resolved characterization of nanomaterials.
Materials Science
Time-resolved photoluminescence emission spectrum with three peaks from different layers. Adapted from Buschmann et al., J Appl Spectrosc 80, 449–457 (2013).
Materials Science
Representative surface structure of a solar cell used for optical characterization studies.
Materials Science

Application Examples

Time-resolved emission spectra (TRES) of a GaAsP quantum well heterostructure excited at 595 nm and recorded from 630–900 nm. Distinct emission peaks at 650 nm, 735 nm, and 860 nm originate from the Al₀.₄Ga₀.₆As barrier, the GaAsP quantum well, and the n-GaAs/substrate layers. Global multi-exponential analysis reveals layer-specific charge carrier dynamics within the multilayer system. Adapted from Buschmann et al., J Appl Spectrosc (2013).

Layer-Resolved Charge Carrier Dynamics by Spectrally Resolved TRPL

Time-resolved emission spectra (TRES) were recorder using PicoQuant’s FluoTime 300 Photoluminescence Spectrometer to separate charge carrier dynamics in a GaAsP quantum well heterostructure. Emission peaks at 650 nm, 735 nm, and 860 nm are assigned to the Al₀.₄Ga₀.₆As barrier, the GaAsP quantum well, and the n-GaAs layer and the GaAs substrate. Layer-specific lifetimes reveal distinct recombination dynamics within the multilayer system.

Three-dimensional representation of time-resolved emission spectra of tryptophan in saline buffer. Thirty-one wavelength-resolved decay curves were recorded and globally analyzed, revealing three characteristic lifetimes of 360 ps, 2.5 ns, and 7.4 ns.

Time-Resolved Emission Spectra of Tryptophan

Time-resolved emission spectra (TRES) of tryptophan in saline buffer were recorded using PicoQuant’s FluoTime 300 Photoluminescence Spectrometer. Thirty-one wavelength-resolved decay curves were globally analyzed, revealing three characteristic lifetimes of 360 ps, 2.5 ns, and 7.4 ns, reflecting heterogeneous excited-state dynamics.

Related Methods

oft-confinement processing of a sub-micrometer polymer film using a patterned PDMS stamp, illustrating controlled structuring and morphology formation after UV cross-linking. Taken form Feng et al., ACS Nano, 10, 1, 150-158 (2016).

Photoluminescence (PL)

A steady-state spectroscopy method that measures the intensity of light emitted from a material under continuous excitation. It provides insights into electronic band structure, defect states, and optical quality but does not capture temporal emission dynamics.

TRPL decay curves illustrating time-dependent photoluminescence and varying carrier lifetimes in advanced materials.

Time-Resolved Photoluminescence (TRPL)

A time-resolved spectroscopy method that measures the temporal decay of photoluminescence after pulsed excitation. It provides insights into charge carrier lifetimes, recombination pathways, and defect-related dynamics in materials but does not resolve spatial variations across a sample.

Top: TRPL image of a CIGS solar cell acquired with SNSPD detector, bottom: Normalized photoluminescence decay curve in bulk material (red) and at a defect site (blue).

Time-Resolved Photoluminescence Imaging (TRPL Imaging)

A spatially resolved extension of time-resolved photoluminescence that maps carrier lifetimes across a sample surface. It enables visualization of local recombination dynamics, diffusion effects, and material inhomogeneities but typically does not capture full spectral evolution over time.

In-Depth Scientific Resources

Premium Resources

Access in-depth application notes and scientific posters with detailed methods, measurement data, and real-world use cases.

Customer Video: Study of Defects in Metal Halide Perovskites

In this customer video, Prof. Jinsong Huang (University of North Carolina) discusses how electronic defects affect efficiency and stability in perovskite solar cells and how FLIM helps visualize their impact.

Application Note: TRPL and Electroluminescence Characterization

This application note demonstrates time-resolved photoluminescence and electroluminescence measurements of quantum dot LEDs

Poster: Wafer Characterization

Poster on wafer characterization using time-resolved photoluminescence and TCSPC to analyze charge carrier dynamics in semiconductor materials.

Application Note: Measuring Steady-state and Time-Resolved Photoluminescence

Learn how time-resolved fluorescence techniques reveal excited-state dynamics and charge-carrier processes in materials.

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