Book Chapter: Charge Recombination in Organic Solar Cells

I have my first scientific book chapter out.

It’s entitled Charge Recombination in Organic Solar Cells and part of the book Soft-Matter Thin Film Solar Cells: Physical Processes and Device Simulation, which was published today in the brand new book collection of AIP Publishing.

The chapter is aimed as a primer for beginners in the field who want to learn how recombination in organic solar cells works and how it limits the device performance. As always, by organic solar cells I mean those which consist of two different materials, a donor and an acceptor, finely mixed together in a nanoscale network called bulk heterojunction.

My idea was to follow the elementary steps it takes for photo-generated charge carriers within this structure to finally leave the device at the electrical contacts. For each step I then took a look at the concurrent loss processes, the most important of which are geminate and non-geminate recombination in the bulk, as well as surface recombination.

But let’s not go into any more detail. For all of you interested, here is the table of contents, which should give you a good idea of what you can read about in the chapter:

  • Introduction
  • Geminate recombination
    • The Onsager-Braun model and its limitations
    • Delocalization, disorder, and energy bending
    • Experiments to monitor geminate recombination
  • Non-geminate recombination in the bulk
    • Langevin recombination and beyond
    • Effect of phase separation
    • Non-encounter-limited recombination
    • Charge carrier trapping
    • Consequences of non-geminate recombination from a device perspective
  • Recombination at the contacts
    • Selective and non-selective contacts
    • Extraction barrier

For a scientist, there is not much to gain from writing a book chapter. You put an incredible amount of work into it, while the things hardly ever get cited. However, I still enjoyed it. For one, it was one of the little projects that kept me sane over lockdown. It also gave me the opportunity to summarize what I’ve learned through my research over the last ten years.

Actually, I liked it so much that I’m thinking about writing a more detailed review article on some of the aspects, which may or may not come into existence at some point. Stay tuned!


Sebastian Wilken, Charge Recombination in Organic Solar Cells. In: Soft-Matter Thin Film Solar Cells: Physical Processes and Device Simulation, edited by J. Ren and Z. Kan, AIP Publishing, Melville, New York (2020)