New camera technique tracks excitons in real time, opening fresh routes for better solar materials

Researchers have unveiled a cutting-edge imaging method that captures the fleeting paths of excitons — the light-generated charge carriers crucial in solar cells and other optoelectronic devices. The team behind the study, published in ACS Photonics, built a camera from an array of single-photon avalanche diodes (SPADs) which can detect individual photons as excitons emit light while moving through a material.

Until now, observing both where excitons travel and how long they live has been challenging, especially in real materials under realistic conditions. The SPAD camera sidesteps key limitations: it records full-field images rather than requiring a point-by-point scan, works under lower light levels, and extracts rich spatiotemporal data about exciton behaviour.

In practical tests, the method permitted researchers to map how far excitons diffuse, how quickly they recombine, and how their trajectories vary inside the material. These insights are critical because the movement and lifetime of excitons directly impact how efficiently a solar cell can convert light into electricity.

The implications are promising. By applying this technique to candidate light-harvesting materials, scientists can now link microscopic exciton dynamics with the macroscopic performance of devices. That means better feedback for designing materials with fewer losses and higher efficiencies.

Going forward, the team envisions using the SPAD-camera approach to study a wide range of emergent materials — from novel perovskites to organic semiconductors — pushing the frontier of high-performance photovoltaics and optoelectronics.

This development marks a significant step in materials characterization, bringing into view what was once invisible: how excitons dance, diffuse and disappear in the blink of an eye.

Link to the article

Key points:

• The authors developed a wide-field photoluminescence detection approach where the SPAD camera captures individual photon emission events from excitons, enabling mapping of both spatial trajectories and temporal dynamics.
• This technique is suited for studying materials designed for light-harvesting (e.g., photovoltaics) because tracking how excitons move and recombine gives insight into efficiency-limiting processes.
• The method allows imaging under relatively low light intensities and without scanning (i.e., capturing a full field at once), which is an advantage over some conventional techniques.
• The authors demonstrate the ability to resolve exciton diffusion lengths and lifetimes in chosen sample materials, providing a quantitative view of exciton behaviour in situ.
• They suggest this could assist in the design of next-generation optoelectronic and photovoltaic materials by linking microscopic exciton behaviour to macroscopic device performance.