A research team led by Imec, that also included teams from Hasselt University and Kuwait University, has fabricated a perovskite solar module based on a scalable, stable device stack that can be processed with industry-compatible techniques, such as sputtering, evaporation, and slot-die coating.
The panel is based on 17%-efficient perovskite solar cells built with a p-i-n configuration, an electron transport layer made of nickel(II) oxide (NiOx), a perovskite layer deposited via slot-die coating, an electron transport layer made of buckminsterfullerene (C60) and lithium fluoride (LiF), a bathocuproine (BCP) buffer layer, and a copper (Cu) electrode.
The scientists constructed a 56-cell monofacial panel with an active area of 784 cm2, a power conversion efficiency of 13.08%, and a geometrical fill factor (GFF) of about 89%. They then built a second bifacial module by replacing the Cu electrode with one based on indium tin oxide (ITO).
“Under thermal and light stress, the electrode metals like Cu, Au, Ag, etc. are known to diffuse into the perovskite layer and thus compromise long-term stability, whereas devices with transparent conductive electrodes have shown much better stability under accelerated aging,” the researchers explained. “The ITO has lower conductivity as compared to metal electrodes, which can lead to resistive losses and consequently a lower fill factor. To minimize that, we created a module design with reduced subcell width leading to 93 subcells.”
The bifacial panel has an aperture area of 781 cm2 and is able to achieve a power conversion efficiency of 11.9%.
“Moreover, the encapsulated bifacial mini-modules (4 cm2) developed exhibited high tolerance to the IEC 61215-based damp heat [85 C, 85% relative humidity (RH)], the best ones retaining around 92% of initial efficiency after 1,000 hours,” the team said, noting that interfacial passivation could further increase the efficiency of the device.
The researchers stated that the results show that the proposed device stack is thermally stable, and that encapsulation is robust enough to ensure stability.
