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Colombian scientists have proposed developing inverted perovskite solar cells with a hole transport layer based on indium-doped nickel oxide. The result is a champion device that achieves an efficiency of 20.06% and shows remarkable stability.
A group of researchers from the Universidad de los Andes in Colombia has developed for the first time an inverted perovskite solar cell with a hole transport layer (HTL) based on doped nickel oxide (NiOx) layers. with Indian (In).
Inverted perovskite cells have a device structure known as a “pin,” in which the p-hole-selective contact is at the bottom of the intrinsic perovskite layer i with the electron transport layer n on top. Conventional halide perovskite cells have the same structure but inverted: a “nip” arrangement. In the nip architecture, the solar cell is illuminated through the electron transport layer (ETL) side; in the pin structure, it illuminates through the surface of the hole transport layer (HTL).
The scientists explained that NiOx has an energy gap of more than 3.5 eV, exceptional chemical stability, durability, low toxicity and cost-effective processing. “In the case of NiOx-based inverted perovskite solar cells, the doping method has paved the way for HTL optimization, often through observable improvements also at the interface level and in the perovskite layer.” , they added.
The team built the NiOxIn HTL using a one-step electrochemical deposition (ECD) process, which they explained offers low processing temperature, precise control of layer thickness, adhesion and structure, as well as low generation of chemical waste.
The cell was fabricated with an indium tin oxide (ITO) substrate, the NiOxIn HTL, a perovskite absorber, an electron transport layer based on phenyl-C61-butyric acid methyl ester (PCBM), a buffer bathocuproin (BCP) and a silver (Ag) metallic contact.
“The approximate thickness of each layer of the solar cell was 28 nm for the NiOxIn layers, 430 nm for the perovskite layer, 30 nm for the PCBM layer, and 125 nm for the silver layer,” the group explained.
The champion cell built with the proposed architecture achieved a power conversion efficiency of 20.06%, an open circuit voltage of 1.10 V, a short circuit current density of 23.40 mA cm-2, and a fill factor of 78.10%.
Through a series of maximum power point tracking (MPPT) tests, the researchers also found that the cell was able to maintain its performance under real operating conditions for more than 3,000 s.
“By monitoring cell performance for 46 days, all devices were found to be stable and no effect of indium doping was observed,” they stated. “SEM and XRD tests of the perovskite layer indicated that In doping of NiOx has a notable effect on increasing the grain and crystallite size of the absorber.”
The novel solar cell design was presented in the article “ Enhanced inverted perovskite solar cells via indium doped nickel oxide as hole transport layer ,” recently published in Solar Energy . “The results show for the first time that indium doping of NiOx is a novel and effective option to improve the photovoltaic performance of inverted perovskite solar cells,” the academics conclude. |
