Researchers from Colombia's Universidad de los Andes recently set out to develop inverted perovskite solar cells (IPSCs) with a hole transport layer based on indium-doped nickel oxide. The result is a champion device that achieved an efficiency of 20.06% with remarkable stability.
The team explained that NiOx has an energy gap of over 3.5 eV, exceptional chemical stability, durability, low toxicity, and cost-effective processing. The scientists said that in the case of NiOx-based inverted perovskite solar cells, the doping approach has indeed paved the way for HTL optimization, frequently through observable improvements also at the interface level and in the perovskite layer.
The team built the NiOxIn HTL via a one-step electrochemical deposition (ECD) process, which is said to offer low processing temperature, fine control of thickness, adhesion and layer structure, as well as low generation of chemical waste.
The cell was fabricated with a substrate made of indium tin oxide (ITO), the NiOxIn HTL, a perovskite absorber, an electron transport layer based on phenyl-C61-butyric acid methyl ester (PCBM), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
The team specified that the approximate thickness of each layer within 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 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 the IPSCs performance for 46 days, all the devices were found to be stable and no effect of indium doping was observed. SEM and XRD tests of the perovskite layer indicated that the In doping of NiOx has a remarkable effect by increasing the grain and crystallite size of the absorber", the team said.
“The results show for the first time that indium doping of NiOx is a novel and efficient option to improve the photovoltaic performance of inverted perovskite solar cells,” the scientists concluded.
