Scientists in Spain have developed an amorphous silicon solar cell that can be used in both transparent solar photovoltaics and tandem applications. The device reportedly achieves remarkable levels of efficiency and could provide an alternative to transparent organic solar photovoltaics.
A research group from the Spanish Universitat Politècnica de Catalunya (UPC) has manufactured a transparent solar cell based on a light absorber made of amorphous hydrogenated silicon carbide (a-Si1xcX:H) thin films.
“Our cell shows one excellent transparency of more than 50% for inorganic transparent solar photovoltaics”, said the lead author of the study, Gerard Masmitjà pv magazinenoting that amorphous silicon-based solar cells have regained interest in recent years as a promising option for implementing highly reliable transparent devices. “We have demonstrated that tuning the a-Si1xcX:H-bandgap is possible, which is not only advantageous for transparent solar cells, but could also have applications in tandem devices.”
The 0.5 cm x 0.5 cm solar cell was also built with a commercial glass substrate coated with fluorine-doped tin oxide (FTO).
The 40-45 nm a-Si1xcX:H absorber was deposited on a borosilicate glass substrate by plasma enhanced chemical vapor deposition (PECVD) with different SiH4/CH4 ratios, while a 45 nm aluminum-doped zinc oxide (AZO) hole transport layer was deposited by atomic layer deposition (ALD), which was also used to deposit a 12 nm thick hole-selective contact of vanadium oxide (V).2OX).
For the electron transport layer (ETL), the research team used a wide bandgap phosphor-doped a-Si1xcX:H movie. Diethylzinc (DEZ), Trimethylaluminum (TMA) and DI-H2O were used as precursors of zinc, aluminum and oxidizing agent.
The scientists analyzed the microstructure of the a-Si1xcX:H solar cell via scanning transmission electron microscope (STEM) images recorded with the JEOL bright-field (BF) and high-angle annular dark-field (HAADF) detectors. They used a JEOL F200 TEM ColdFEG operated at 200 kV, placing samples in a JEOL beryllium double-tilt holder for energy dispersive X-ray spectroscopy (EDS).
The best solar cell fabricated with the proposed architecture achieved an energy conversion efficiency of 2.6%, an open-circuit voltage of 748 mV, a short-circuit current of 5.2 mAcm2, and a fill factor of 68%. “Higher carbon content in a-Si1xcX:H improves efficiency under indoor lighting conditions,” explains Masmitjà.
Some devices also showed average photopic transmittance (APT) values ranging from 50% to 70%. This metric defines transparency to the human eye rather than providing a simple arithmetic average. It recently became a critical benchmark for applications such as solar windows and semi-transparent PV cells.
“This demonstrates that truly transparent, non-organic solar cells can be achieved while maintaining remarkable energy conversion efficiency,” the researchers said. “In addition to transparency, the integration of carbon also improves the suitability of these devices for indoor applications, as their efficiency is better maintained under low-light conditions.”
The cell was described in “Transparent solar cells based on a-Si1xcX:H alloys: from silicon to carbon-rich absorbers”, published in Renewable energy.
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