The researchers at the Belgian research institute applied a two-layer treatment to the perovskite absorber, which they say improved the efficiency and stability of the cells. The device achieved a breakdown voltage of 1.17 V, a short-circuit density of 24.5 mA/cm2 and a duty cycle of 84.6%.
The cell has a pin structure, which means that the perovskite cell material is deposited on a hole transport layer and then coated with an electron transport layer – the opposite of traditional pin device architecture. Inverted perovskite solar cells typically exhibit strong stability, but have lagged behind conventional devices in terms of conversion efficiency and cell performance.
The device also utilizes the “upper” interface between the perovskite and the buckminsterfullerene (C60) electron transport layer, and the “lower” interface between the perovskite and the hole transport layer made of nickel(II) oxide (NiOx). Both interfaces were treated with an ammonium salt known as 2-thiopheneethylammonium chloride (TEACl). The results were compared.
The researchers said the double-layer treatment improved efficiency, with a relative power conversion efficiency (PCE) increase of 9% compared to an untreated reference device.
“Optimizing these interfaces can therefore minimize losses and improve energy harvesting, which improves device efficiency and operational stability,” the researchers noted, noting that this architecture creates a 2D perovskite layer at the interface. Cells with this configuration usually have large exciton binding energies and are generally more stable than conventional 3D devices due to the protection provided by the organic ligands.
Fully described in “Inverted Perovskite Solar Cells and Modules” Minimization of Interface Losses. ACS Energy Letterscell achieved a power conversion efficiency of 24.3%, an open circuit voltage of 1.17 V, a short circuit density of 24.5 mA/cm2, and a fill factor of 84.6%.
“In addition to the increase in efficiency, we also observed remarkable stability,” said Tom Aernouts, Research and Development Manager for the Thin-Film Photovoltaics team. “Indeed, after 1,000 hours of continuous use under single sun illumination, the devices maintained 97% performance, which is among the best available today.”
The team also found that the cell retained 88% of its original performance after 1,850 hours, compared to 55% for untreated cells.
The academics also used the cells to make a 3.63 cm2 mini-module with an efficiency of 22.6% and a fill factor of 82.4%. “However, the commercialization of such applications requires industry-compatible processing technologies that solve, among other things, the current stability problems,” they elaborated.
