| Work Detail |
Researchers at Delft University of Technology in the Netherlands have fabricated a heterojunction, interdigitated back-contact solar cell that uses a thin layer of full-area molybdenum oxide as a coating layer. The device guarantees the existence of well-passivated holes between the electron and hole collecting regions.
Scientists at Delft University of Technology in the Netherlands have designed a solar cell with an interdigitated back contact (IBC) and heterojunction (HJT) architecture that uses an oxide-based electron-harvesting contact stack. of molybdenum (MoOx).
MoOx is a transition metal oxide (TMO) nanomaterial that exhibits both novel nanoeffects and excellent semiconducting properties.
“We show that the use of such a fine MoOx minimizes derivatization losses thanks to its low lateral conductivity, while allowing the manufacturing process to be simplified,” the lead author of the research, Katarina Kovacevic, explained to pv magazine . “In the presented structure, MoOx acts as a hole transport layer, while electron capture takes place through a novel layer stacking.”
The research group explained that, in the proposed cell design, the holes are collected through a stack formed by a thin intrinsic layer of hydrogenated amorphous silicon (a-Si:H), MoOx and transparent conductive oxides (TCO). , while the electrons are collected through a blanket layer made of a-Si:H, nc-Si:H, MoOx and TCO.
“MoOx has been selected because it is characterized by lower lateral conductivity compared to doped hydrogenated nanocrystalline silicon (nc-Si:H),” the researchers say. “In the proposed architecture, a thin layer of MoOx is deposited as a blanket on the entire back face of the device on a prepatinated nc-Si:H layer.”
The scientists built the cell with an indium tin oxide (ITO) substrate, the coating layer made of a-Si:H, nc-Si:H, MoOx, an absorber made of n-type monocrystalline silicon, passivating contacts based on polysilicon and silicon monoxide (SiOx), and a silver (Ag) metallic contact.
“In addition to the novel contact stack, our architecture is a great platform for testing industry-relevant processes,” Kovacevic further explained. “First of all, contacts without Ag and without ITO can be easily implemented. Second, because TMOs can be deposited much faster than p-type silicon thin films, the industry can benefit from higher throughput. Third, our high-efficiency IBC solar cells can become cost-effective ingredients for future perovskite-silicon three-terminal tandem devices.”
The team of researchers tested the performance of a 4.05 cm2 solar cell built with this configuration under standard lighting conditions and the device achieved a power conversion efficiency of 21.14%, an open circuit voltage of 689 mV, a short circuit current density of 39.02 mA/cm2 and a fill factor of 78.61%.
The academics attributed the good performance of the champion device to the optimization of the manufacturing flowsheet and the precision of the photolithographic pattern, which they said ensured well-defined and passivated gaps between the electron-hole collecting regions.
“Guided by optoelectric simulations, further optimization of the manufacturing process, fine-tuning of plasma treatments, MoOx and (n)nc-Si:H coating, and introduction of improved ARC(s) are expected to facilitate efficiencies well above 24% in the short term with the proposed architecture,” they added.
The novel cell architecture was presented in the paper “ Interdigitated -back-contacted silicon heterojunction solar cells featuring novel MoOx-based contact stacks. ” , published in Progress in Photovoltaics .
The same research group built an HJT cell based on a MoOx hole collector in 2022. The device achieved a power conversion efficiency of 23.83% and a fill factor of 82.18%. “The certified efficiency is – as far as we know – the highest to date in this type of device,” Isabella said at the time. “The previous record had been certified by the École polytechnique fédérale de Lausanne (EPFL) with 23.5%.” |
