The role of charge recombination to triplet excitons in organic solar cells

Nature Springer Nature 597:7878 (2021) 666-671

Authors:

Alexander J Gillett, Moritz K Riede, Alberto Privitera, Rishat Dilmurat, Akchheta Karki, Deping Qian, Anton Pershin, Giacomo Londi, William K Myers, Jaewon Lee, Jun Yuan, Seo-Jin Ko, Feng Gao, Guillermo C Bazan, Akshay Rao, Thuc-Quyen Nguyen, David Beljonne, Richard H Friend

Abstract:

The use of non-fullerene acceptors (NFAs) in organic solar cells has led to power conversion efficiencies as high as 18%<sup>1</sup>. However, organic solar cells are still less efficient than inorganic solar cells, which typically have power conversion efficiencies of more than 20%<sup>2</sup>. A key reason for this difference is that organic solar cells have low open-circuit voltages relative to their optical bandgaps<sup>3</sup>, owing to non-radiative recombination<sup>4</sup>. For organic solar cells to compete with inorganic solar cells in terms of efficiency, non-radiative loss pathways must be identified and suppressed. Here we show that in most organic solar cells that use NFAs, the majority of charge recombination under open-circuit conditions proceeds via the formation of non-emissive NFA triplet excitons; in the benchmark PM6:Y6 blend<sup>5</sup>, this fraction reaches 90%, reducing the open-circuit voltage by 60 mV. We prevent recombination via this non-radiative channel by engineering substantial hybridization between the NFA triplet excitons and the spin-triplet charge-transfer excitons. Modelling suggests that the rate of back charge transfer from spin-triplet charge-transfer excitons to molecular triplet excitons may be reduced by an order of magnitude, enabling re-dissociation of the spin-triplet charge-transfer exciton. We demonstrate NFA systems in which the formation of triplet excitons is suppressed. This work thus provides a design pathway for organic solar cells with power conversion efficiencies of 20% or more.

Organic Electronics and Beyond

ADVANCED OPTICAL MATERIALS 9:14 (2021) ARTN 2101108

Authors:

Malte C Gather, Bjorn Lussem, Sebastian Reineke, Moritz Riede

Organic Electronics and Beyond (Advanced Optical Materials 14/2021)

Advanced Optical Materials Wiley 9:14 (2021)

Authors:

Malte C Gather, Björn Lüssem, Sebastian Reineke, Moritz Riede

Perspectives of Organic and Perovskite‐Based Spintronics (Advanced Optical Materials 14/2021)

Advanced Optical Materials Wiley 9:14 (2021)

Authors:

Alberto Privitera, Marcello Righetto, Franco Cacialli, Moritz K Riede

Thermally Evaporated Donor Molecules for Low-Voltage Loss Organic Solar Cells

Fundacio Scito (2021)

Authors:

Pascal Kaienburg, Helen Bristow, Anna Jungbluth, Irfan Habib, David Beljonne, Moritz Riede