| Work Detail |
Scientists in Japan developed a 4.49%-efficient solar cell based on titanium dioxide and selenium. The devices is based on a new approach aimed at reducing interfacial recombination and increasing open-circuit voltage and efficiency.
Researchers at the Ritsumeikan University in Japan have fabricated a heterojunction solar cell that utilizes a window layer made of titanium oxide (TiO2) and an absorber based on selenium (Se). The novel device relies on a new architecture that reportedly increases the typical “insufficient” shunt resistance that characterizes these PV cells.
“We developed an innovative approach for forming crystallized Se (c-Se) using a stacked precursor based on Se and Tellurium (Te), with an accurate control of the interfacial Te content,” the researchs corresponding author, Taizo Kobayashi, told pv magazine. “The aim is to enhance the adhesion between the TiO2 and Se layers while limiting the detrimental effects of Te enrichment in terms of carrier transport, resulting in a significant improvement of the power conversion efficiency of TiO2/Se heterojunction photovoltaic devices.”
The scientists explained that the key to their achievement was minimizing low resistive regions near the pn junction caused by Te accumulation, which increases interfacial recombination and is detrimental to the cells open-circuit voltage and overall efficiency. They utilized “commonly used” equipment to apply a resistance heating evaporation technique in the manufacturing process.
“This advancement provides a practical solution to overcome the difficulties associated with forming a uniform Te adhesion layer, making it accessible and applicable to a wider range of researcher groups,” they further explained.
The group built the solar cell with a substrate made of glass and indium tin oxide (ITO), a buffer layer made of zinc magnesium oxide (ZnMgO), the TiO2 window layer, a Se absorber, a buffer layer made of molybdenum trioxide (MoO3), and a gold (Au) metal contact.
“A 5 nm 1st-Se layer appears to be the sweet spot allowing for a higher degree of control of the interface Te while limiting its detrimental influence on carrier transfer,” the team further explained. ”
Tested under standard illumination conditions, the solar cell achieved a power conversion efficiency of 4.49%, an open-circuit voltage of 0.795 V, a short-circuit density of 11.13 mA/cm2, and a fill factor of 50.7%. The devices showed higher open-circuit voltage and decreased dark leakage current values compared to similar devices developed in previous scientific work.
“Particularly, when the thickness of the 1st-Se layer was 5 nm, significant enhancements in open-circuit voltage and efficiency were achieved as compared to devices fabricated by a conventional process,” the academics emphasized. “The introduction of a 5 nm thick 1st-Se layer in 1st-Se/Te/2nd-Se played a pivotal role to promote the orientation and to finely control the Te/(Te + Se) ratio for efficient TiO2/Se photovoltaic devices close to the state of the art.”
They introduced the new cell technology in the study “TiO2/Se heterojunction photovoltaic device made from Se/Te/Se stacked precursor,” published in Solar Energy Materials and Solar Cells. |
