Berlin lab solves perovskite solar's stability problem with graphene-oxide fix

Researchers at Helmholtz-Zentrum Berlin (HZB) have addressed a critical stability issue in perovskite solar cells by introducing a graphene oxide (GO) interface. Their study, published in Joule, demonstrates a triple-junction perovskite solar cell achieving a 27.3% certified power conversion efficiency, maintaining over 90% of this efficiency after 770 hours of operation. This advancement tackles the longstanding problem at the interface between the tin-lead perovskite bottom subcell and the hole transport layer, traditionally made from PEDOT:PSS, which has been prone to chemical degradation.

The HZB team, in collaboration with the University of Potsdam, Technical University Berlin, and Empa, replaced PEDOT:PSS with a two-layer combination of graphene oxide and a self-assembled monolayer (SAM). This new interface prevents the chemical reactions that degrade the tin-lead absorber, while also improving light absorption by eliminating parasitic losses. The GO/SAM bilayer enhances the stability and efficiency of the solar cells, doubling the operational lifetime compared to previous designs.

Perovskite semiconductors offer advantages such as lightweight properties and compatibility with flexible substrates, unlike traditional silicon. The all-perovskite multi-junction architecture can potentially be manufactured using low-cost roll-to-roll methods, opening possibilities for applications in flexible and lightweight photovoltaic products. However, the 770-hour stability milestone, while significant, remains below the commercial viability threshold of 20,000 to 25,000 hours required for long-term warranties.

The study provides a detailed blueprint for the GO/SAM interface, which can be adopted by other laboratories to further develop this technology. The HZB team aims to achieve efficiencies above 30% and five-year operational stability, setting a benchmark for future research. This work highlights that the chemical instability in all-perovskite triple-junction cells is a solvable engineering challenge, paving the way for further advancements in the field.