Seeing photovoltaic devices in a new light

Osaka University researchers have measured the photovoltaic properties of antimony sulfiodide:sulfide devices and discovered a voltage that depends on the wavelength of incident light, which could help develop new light-sensitive and imaging devices

Photovoltaic (PV) devices – such as solar cells and photodiodes – that convert light energy into electronic power are important as renewable energy sources or as light/image sensors. Recent advances in thin film PV devices have attracted much attention due to their low-cost process, flexibility and light weight. Although several PV devices have been reported to date, reversible and fast wavelength-dependent responses have not been observed before. To discriminate between irradiation colors using a single photodiode, a liquid crystal filter capable of electronically switching the absorption color range must be used. However, these filters are bulky; being able to perform color detection without the need for such filters would be helpful in minimizing the size of photovoltaic devices.

Now, a team of researchers from Osaka University has built new photovoltaic devices made of antimony sulfiodide:sulfide composite and found a new effect. The generated voltage could be changed by changing the light color, with ultraviolet lowering the output voltage. That is, a reversible change in the current versus voltage curves can be obtained by simply shining different colors of light on the device. “Such a dramatic shift in voltage is not observed in silicon, perovskites or organic solar cells,” explains first author Ryosuke Nishikubo.

To better understand the mechanism behind this effect, the scientists next performed transient photovoltage (TPV) and photoinduced charge extraction by increasing the voltage linearly (photo-CELIV). These experiments helped elucidate the dramatic 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, generated by high energy charges. These interfacial energy traps significantly reduced the output voltage, and as a result, light of certain energies could be distinguished based on the voltage. This change could be enhanced by the presence of the vapor of 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,” said senior author Akinori Saeki.

The newly discovered phenomenon can be applied to 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 space satellites and microphotography. In addition, it is also potentially desirable as a renewable energy source, due to its low toxicity and low production costs.

Fig.1 Photo of SbSI and SbSI:Sb2S3 photovoltaic devices.

Original Content, Ryosuke Nishikubo

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Fig.2 Device structure (left) and scheme of current density-voltage (JV) characteristics.

This figure is taken from the original paper (Figure 1a).

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Fig.3 JV characteristics of a SbSI:Sb2S3 photovoltaic device under simultaneous irradiation of ultraviolet (UV) and visible (VIS) light with varying intensity ratios. This figure is taken from the original paper (Figure 2e).

CC BY, 2022 Ryosuke Nishikubo et al., Unprecedented wavelength dependence of an antimony chalcohalide photovoltaic device. Advanced functional materials

/public release. This material from the original organisation/author(s) may be of a point in time, edited for clarity, style and length. The views and opinions are those of the author(s). View full here

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