Affiliation:
1. Molecular Materials and Nanosystems and Institute for Complex Molecular Systems Eindhoven University of Technology P.O. Box 513 Eindhoven 5600 MB The Netherlands
2. Integrated Circuits Departments of Electrical Engineering Eindhoven University of Technology P.O. Box 513 Eindhoven 5600 MB The Netherlands
3. TNO/Holst Centre High Tech Campus 31 Eindhoven 5656 AE The Netherlands
4. Dutch Institute for Fundamental Energy Research De Zaale 20 Eindhoven 5612 AJ The Netherlands
Abstract
AbstractTrap states in organic semiconductors are notoriously detrimental to the performance of organic electronics. However, the origin and energetics of trap states remain largely elusive and under debate, especially for bulk‐heterojunction (BHJ) photodiodes consisting of electron donor and acceptor materials. Combining three sensitive techniques now enables locating the origin and energy of trap states in six state‐of‐the‐art polymer – non‐fullerene acceptor organic photodiodes (OPDs) with noise‐based specific detectivities exceeding 1013 Jones. Analyzing the temperature dependence of the reverse‐bias dark current density (Jd) identifies intra‐gap states in the polymers, lying 0.3−0.4 eV above the energy of the highest occupied molecular orbital, as being responsible for Jd. Sub‐bandgap external quantum efficiency spectra of donor‐only and acceptor‐only diodes confirm that intra‐gap states are much more abundant in the polymers. Likewise, responsivity measurements at ultra‐low light intensities (10−7 mW cm−2) show trap‐mediated charge recombination in BHJ and polymer‐only diodes, but not in acceptor‐only devices. The results imply that to further improve the specific detectivity of near‐infrared OPDs, the intra‐gap state energy, and density need to be reduced.
Funder
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Ministerie van Economische Zaken
Subject
Electrochemistry,Condensed Matter Physics,Biomaterials,Electronic, Optical and Magnetic Materials
Cited by
8 articles.
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