Perovskite solar cells: Interfacial loss mechanisms revealed
The SAM layer between the perovskite semiconductor and the ITO contact consists of a single layer of organic molecules. The mechanisms by which this SAM layer reduces losses can be quantified by measuring the surface photovoltage and photoluminescence. © HZB
Metal-organic perovskite materials promise low-cost and high-performance solar cells. Now a group at HZB managed to de-couple the different effects of self-assembled monolayers of organic molecules (SAMs) that reduce losses at the interfaces. Their results help to optimise such functional interlayers.
Losses occur in all solar cells. One cause is the recombination of charge carriers at the interfaces. Intermediate layers at such interfaces can reduce these losses through so-called passivation. Self-assembled monolayers (SAMs) with a carbazole core are particularly well suited for the passivation of semiconductor surfaces made of perovskite materials. A team led by HZB physicist Prof. Steve Albrecht together with a group from Kaunas Technical University in Lithuania demonstrated this some time ago, developing a silicon-perovskite-based tandem solar cell with a record efficiency of over 29 %.
Now, for the first time, a team at HZB has analysed the charge carrier dynamics at the perovskite/SAM-modified ITO interface in more detail. From time-resolved surface photovoltage measurements, they were able to extract the density of "electron traps" at the interface as well as the hole transfer rates using a minimalist kinetic model. Complementary information was provided by measuring the time-resolved photoluminescence.
"We were able to determine differences in passivation quality, selectivity and hole transfer rates depending on the structure of the SAM, and demonstrate how the time-resolved surface photovoltage and photoluminescence techniques are complementary," explains Dr. Igal Levine, postdoc at HZB and first author of the paper. Time-resolved surface photovoltage proves to be a relatively simple technique for quantifying charge extraction at buried interfaces that could significantly facilitate the design of ideal charge-selective contacts.
- 83 pupils at Girls'Day at HZBOn 23 April 2026, the annual Girl’s Day took place, giving pupils an insight into various career paths in the fields of science and technology. 83 pupils visited the Adlershof and Wannsee sites and enjoyed a day full of exciting experiments.
- Electrocatalysts: New model for charge separation at the solid-liquid interfaceHydrogen is at the heart of the transition to carbon neutrality, as both an energy carrier and a reagent for green chemistry. However, large-scale production of hydrogen via electrolysis, as well as the production of many other chemical products, requires significantly cheaper and more efficient catalysts. A precise understanding of the electrochemical processes that take place at the interface between the solid catalyst and the liquid medium is highly useful for developing better electrocatalysts. In the journal Nature Communications, an European team has now presented a powerful model that determines charge separation at the interface, the formation of the electric double layer and local electric potential variations, and the resulting influence on the catalytic activity.
- Theory meets practice – We’re heading back to HTW Berlin!The HZB’s BIPV consultancy office (BAIP) is once again coordinating and delivering the lecture series “Building-Integrated Photovoltaics”.