Study Findings Likely to Lead to New Functional Light-Sensing and Imaging Devices.

New functional devices for light detection and imaging

At the Institute for Open and Transdisciplinary Research Initiatives at University of OsakaScientists have discovered a new feature of solar cells made from antimony sulfiodide: sulfide composite that they called the wavelength-dependent photovoltaic effect (WDPE).

Research findings likely to lead to new functional devices for light detection and imaging.
Photo of SbSI and SbSI:Sb2s3 photovoltaic devices. Image Credit: Ryosuke Nishikubo.

The research group found that changing the color of incident light from visible to ultraviolet caused a reversible change in the output voltage while leaving the generated current unaltered. This work could result in new functional photosensitive and imaging devices.

Photovoltaic (PV) devices – such as photodiodes and solar cells – that convert light energy into electronic power are essential as renewable energy sources or as light or image sensors.

New developments in thin-film PV devices have gained enormous appeal due to their affordable process, light weight and flexibility. Although several PV devices have been reported to date, reversible and fast wavelength-dependent responses have not been noted before.

To distinguish irradiation colors using a single photodiode, it is essential to use a liquid crystal filter that has the potential to electronically switch the absorption color range.

But such filters are huge; being able to perform color detection without the need for such filters would be beneficial for reducing the size of photovoltaic devices.

Currently, a research group at Osaka University has built new photovoltaic devices made of antimony sulfiodide: sulfide composite and discovered a new effect.

The voltage produced could be changed by shifting the light color, with ultraviolet lowering the output voltage. This means that a reversible change in the current versus voltage curves can be achieved by simply shining different colors of light onto the device.

Such a dramatic shift in voltage is not observed in silicon, perovskites or organic solar cells

Ryosuke Nishikubo, lead author of the study, University of Osaka

To better understand the mechanism behind this effect, the researchers performed transient photovoltage (TPV) and photoinduced charge extraction by linearly increasing voltage (photo-CELIV). Such experiments helped verify the significant and reversible change in charge carrier life caused by ultraviolet irradiation.

The team concluded that WDPE was caused by metastable “trap” states at the heterojunction interface, produced by high energy charges. Such interface energy tends to accommodate a significantly reduced output voltage, allowing light to be differentiated from some energies based on voltage. This change could be enhanced by the presence of the vapor obtained from a polar solvent.

While our work advances basic science by explaining this new effect, the research also has many potential applications, including as a vapor detector.

Akinori Saeki, senior study author, University of Osaka

The newly discovered phenomenon could be used in light detection used in everything from cell phones to cars, to security or horticultural systems.

It can also be part of imaging applications in medical and other scientific activities, such as microphotography and space satellites. It can also be useful as a renewable energy source due to its low production costs and low toxicity.

Magazine reference:

Nishikubo, R., et al† (2022) Unprecedented wavelength dependence of a photovoltaic device with antimony chalcohalide. Advanced functional


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