TU Delft researchers have built a tandem perovskite-silicon solar cell with a new approach to interface design. The breakdown voltage of the device is 1.81 V, the short-circuit current is 18.1 mA/cm2 and the fill factor is 75.0%.
“Our findings demonstrate the potential of using (n)nc-SiOx:H and (n)nc-Si:H interfacial layers in tandem solar cells to minimize reflection losses at the interfaces between perovskite and silicon subcells,” said Yifeng. Zhao, lead author of the study. “These light control techniques can be applied to various tandem structures thanks to the optimization of interference effects.”
The perovskite solar cell with an efficiency of 19.1% includes an indium tin oxide (ITO) and glass substrate, a carbazole (2PACz) hole transport layer, a perovskite absorber, a buckminsterfullerene (C60) electron transport layer, a bathocuproine (BCP) buffer layer, and an aluminum (Al) metal contact.
In the tandem device, a nickel(II) oxide layer (NiOx) was used in the recombination junction to reduce electrical shunting. The presence of hydroxyl-rich NiOx facilitated the assembly of 2PACz, leading to a reduction of electrical shunts in the top cells. In addition, an anti-reflection coating based on magnesium fluoride (MgF2) and optimization of the C60 and SnOx layer thickness helped to minimize reflection losses.
The master solar cell achieved a power conversion efficiency of 24.6%, a breakdown voltage of 1.81 V, a short-circuit current of 18.1 mA/cm2 and a duty cycle of 75.0%.
Using (n)nc-Si:H and (n)nc-SiOx:H layers with thicknesses of about 95 nm and 115 nm, respectively, reflection reductions of 1.35 mA/cm2 and 1.51 mA/cm2 were achieved at the interfaces. between the perovskite and the c-Si base cells, which enables better photo-coupling to the base for c-Si solar cells.
They introduced the cell “Monolithic Perovskite/Silicon Tandem Solar Cells Optical Simulation Aided Design and Engineering of Monolithic Perovskite/Silicon Tandem Solar Cells”, published recently ACS Publications. The research group includes researchers from Eindhoven University of Technology and The Netherlands Organization for Applied Scientific Research (TNO).
“This technique can be adapted to different tandem designs to realize optimal light control in tandem devices,” the researchers concluded.