Scientists from Saudi Arabia’s King Abdullah University of Science and Technology (KAUST), Deutsches Elektronen-Synchrotron DESY, Academy of Sciences of the Czech Republic and Slovak Academy of Sciences have demonstrated a power conversion efficiency of 28.1% for a perovskite-silicon tandem solar cell based on textured silicon wafers.
Textured silicon wafers used in silicon solar cell manufacturing offer superior light trapping, which is a critical enabler for high-performance photovoltaics. The team explained that a similar optical benefit can be obtained in monolithic perovskite/silicon tandem solar cells, enhancing the current output of the silicon bottom cell. Yet, such complex silicon surfaces may affect the structural and optoelectronic properties of the overlying perovskite films.
In their recent work, through extensive characterization based on optical and microstructural spectroscopy, the researchers found that the main effect of such substrate morphology lies in an altering of the photoluminescence response of the perovskite, which is associated with thickness variations of the perovskite, rather than lattice strain or compositional changes.
With this understanding, the design of high-performance perovskite/silicon tandems was executed, yielding an efficiency of 28.1% under standard illumination conditions, an open-circuit voltage of 1,851 mV, a short-circuit current of 18.9 mA/cm2, and a fill factor of 80.1%.
The team built the bottom cell on n-type float-zone double-polished wafers. The device uses a tin(IV) oxide (SnO2) buffer layer, an electron transport layer made of buckminsterfullerene (C60), an amorphous silicon (a-Si:H) layer for passivating the wafer surfaces deposited via plasma-enhanced chemical vapor deposition (PECVD), and a solution-deposited perovskite film.
The researchers emphasized that the configuration of the bottom cell need to be tailored to accommodate the perovskite top cell processing, aiming at high tandem performance. The team believes that perovskite-silicon cells could reach higher efficiencies in the future with some adjustments.