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.

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.

arö

  • Copy link

You might also be interested in

  • More time for discussions
    Interview
    12.05.2025
    More time for discussions
    The South African chemist Denzil Moodley is the first Industrial Research Fellow at HZB. He is playing a leading role in the CARE-O-SENE project. The Fellowship program aims to further accelerate the development of an efficient catalyst for a sustainable aviation fuel. An interview about the CARE-O-SENE project and why it is so important for scientists from industry and public research to work together.
  • Perovskites: Hybrid materials as highly sensitive X-ray detectors
    Science Highlight
    08.05.2025
    Perovskites: Hybrid materials as highly sensitive X-ray detectors
    New bismuth-based organic-inorganic hybrid materials show exceptional sensitivity and long-term stability as X-ray detectors, significantly more sensitive than commercial X-ray detectors. In addition, these materials can be produced without solvents by ball milling, a mechanochemical synthesis process that is environmentally friendly and scalable. More sensitive detectors would allow for a reduction in the radiation exposure during X-ray examinations.
  • Electrical energy storage: BAM, HZB, and HU Berlin plan joint Berlin Battery Lab
    News
    07.05.2025
    Electrical energy storage: BAM, HZB, and HU Berlin plan joint Berlin Battery Lab
    The Federal Institute for Materials Research and Testing (BAM), the Helmholtz-Zentrum Berlin (HZB), and Humboldt University of Berlin (HU Berlin) have signed a memorandum of understanding (MoU) to establish the Berlin Battery Lab. The lab will pool the expertise of the three institutions to advance the development of sustainable battery technologies. The joint research infrastructure will also be open to industry for pioneering projects in this field.