How to Reduce Charge Recombination in Organic Solar Cells: There are Still Lessons to Learn from P3HT:PCBM
Artikel i vetenskaplig tidskrift, 2021

Suppressing charge recombination is key for organic solar cells to become commercial reality. However, there is still no conclusive picture of how recombination losses are influenced by the complex nanoscale morphology. Here, new insight is provided by revisiting the P3HT:PCBM blend, which is still one of the best performers regarding reduced recombination. By changing small details in the annealing procedure, two model morphologies are prepared that vary in phase separation, molecular order, and phase purity, as revealed by electron tomography and optical spectroscopy. Both systems behave very similarly with respect to charge generation and transport, but differ significantly in bimolecular recombination. Only the system containing P3HT aggregates of high crystalline quality and purity is found to achieve exceptionally low recombination rates. The high-quality aggregates support charge delocalization, which assists the re-dissociation of interfacial charge-transfer states formed upon the encounter of free carriers. For devices with the optimized morphology, an exceptional long hole diffusion length is found, which allows them to work as Shockley-type solar cells even in thick junctions of 300 nm. In contrast, the encounter rate and the size of the phase-separated domains appear to be less important.

phase separation



organic photovoltaics

charge recombination


Sebastian Wilken

Carl von Ossietzky Universität Oldenburg

Åbo Akademi

Dorothea Scheunemann

Chalmers, Kemi och kemiteknik, Tillämpad kemi

Carl von Ossietzky Universität Oldenburg

Staffan Dahlstrom

Åbo Akademi

Mathias Nyman

Åbo Akademi

Jurgen Parisi

Carl von Ossietzky Universität Oldenburg

Ronald osterbacka

Åbo Akademi

Advanced Electronic Materials

2199-160X (ISSN)

Vol. 7 5 2001056


Fysikalisk kemi


Annan fysik



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