11 Aug Perovskite solar cells: One layer makes the difference
Perovskite multi-junction solar cells make better use of the solar spectrum than single-junction cells. They combine perovskite semiconductors with different bandgaps, thereby increasing efficiency. Researchers at the Helmholtz-Zentrum Berlin (HZB) have now developed a new hole-transport layer that, according to the institute, further improves both the efficiency and long-term stability of perovskite triple-junction solar cells.
Bilayer replaces polymer
The HZB team combined three perovskite semiconductors with different bandgaps into a monolithic triple-junction solar cell. According to the researchers, the study focused on the interconnection layer between the middle and rear subcells. The polymer PEDOT is commonly used as the hole-transport layer but causes optical losses and limits long-term stability. The researchers therefore combined a layer of graphene oxide (GO) with a self-assembled monolayer (SAM). According to HZB, this bilayer improves the interface both morphologically and electronically, enabling more efficient charge transport.
Optical losses reduced
The team then integrated the new layer architecture into the perovskite triple-junction solar cell, replacing the conventional PEDOT layer. This significantly reduced optical losses. According to HZB, the achieved power conversion efficiency of 27.3% ranks among the highest reported so far for this technology.
The new architecture also demonstrated high stability during continuous operation. According to the researchers, the solar cells retained more than 90% of their initial power conversion efficiency after more than 770 hours of operation. Their analyses also indicate that further optimisation of the perovskite and interconnection layers could increase efficiencies to more than 30%.
Original. publication:
[Yeonghun Yun et al.: Triple-junction all-perovskite solar cells with self-assembling hole contacts in all subcells; Joule, 2026, DOI: 10.1016/j.joule.2026.102575]
Source: www.helmholtz-berlin.de
Photo: Laura Canil / HZB