Organic Planar Heterojunction Solar Cells and Photodetectors Tailored to the Exciton Diffusion Length Scale of a Non‐Fullerene Acceptor
planar heterojunctions
exciton diffusion lengths
non-fullerene acceptors
organic solar cells
02 engineering and technology
0210 nano-technology
01 natural sciences
7. Clean energy
organic photodetectors
0104 chemical sciences
DOI:
10.1002/adfm.202208001
Publication Date:
2022-10-19T01:55:34Z
AUTHORS (7)
ABSTRACT
AbstractWhile non‐fullerene acceptors (NFAs) have recently been demonstrated to exhibit long‐range exciton diffusion, most organic photovoltaic and photodetector studies still focus on blended polymer: NFA systems. Herein, a 40 nm exciton diffusion length for IT4F excitons is determined, and it is demonstrated that sharp interface, planar heterojunction (PHJ) IT4F/PM6 devices with the IT4F layer thickness matched to this diffusion length yield optimized photovoltaic and photodetector performance. The PHJ devices yield an enhanced device open‐circuit voltage relative to bulk heterojunction (BHJ) devices, associated with suppressed bimolecular recombination losses. The PHJ architecture also results in a ≈100‐fold increase in electroluminescence (EL) quantum efficiency relative to the BHJ device, correlated with a shift from charge transfer state EL for the BHJ to IT4F exciton dominated EL for the PHJ, attributed to significant hole injection from PM6 into IT4F. Of particular note, the PHJ architecture is shown to suppress dark leakage current, resulting in 83 times higher photodetector detectivity at −2 V bias than the equivalent BHJ device.
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