Researchers from Solliance partners Delft University of Technology, Eindhoven University of Technology and TNO have developed a tandem perovskite-silicon solar cell using a new approach to interface engineering.
The team's 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 the perovskite and silicon sub-cells, as explained by the scientists. Through optimizing interference effects, these light management techniques can be applied to various tandem structures.
The perovskite solar cell, with a 19.1% efficiency, features 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 (NiOx) layer was employed at the recombination junction to reduce electrical shunting. The presence of hydroxyl-rich NiOx facilitated the assembly of 2PACz, resulting in reduced electrical shunts in the top cells. Additionally, an anti-reflective coating based on magnesium fluoride (MgF2) and the optimization of C60 and SnOx layer thickness helped minimize reflection losses.
The champion solar cell achieved a power conversion efficiency of 24.6%, an open-circuit voltage of 1.81 V, a short-circuit current of 18.1 mA/cm2, and a fill factor of 75.0%.
By using (n)nc-Si:H and (n)nc-SiOx:H layers with thicknesses of around 95 nm and 115 nm, respectively, reflection reductions of 1.35 mA/cm2 and 1.51 mA/cm2 were achieved at the intermediate interfaces between the perovskite and c-Si bottom-cells, allowing for better light coupling into the bottom c-Si solar cells.
“This technique can be adapted to different tandem designs to realize optimal light management in tandem devices,” the scientists stated.