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- Title
Limitations of Charge Transfer State Parameterization Using Photovoltaic External Quantum Efficiency.
- Authors
Armin, Ardalan; Zarrabi, Nasim; Sandberg, Oskar J.; Kaiser, Christina; Zeiske, Stefan; Li, Wei; Meredith, Paul
- Abstract
Free carrier photogeneration in bulk‐heterojunction solar cells composed of blends of acceptor and donor organic semiconductors proceeds via intermolecular charge transfer (CT) states. Non‐adiabatic Marcus theory has proven valid to explain the absorption and emission of these sub‐gap states which have extremely weak emission probabilities and absorption cross sections making them difficult to probe directly using optical spectroscopy. Therefore, the CT state parameters involved in the Marcus model are often extracted from fittings on the photovoltaic external quantum efficiency (EQEPV) and electroluminescence. These two spectra are (ideally) interrelated via the so‐called reciprocity principle. In this paper, the limitations of such an approach are demonstrated, in particular the impact of simple low finesse cavity interference effects acting as an uneven spectral filter for emission and absorption. This can produce almost spurious CT state parameterization with, for example, relative errors as large as 90% in absorption coefficients obtained from EQEPV. It is shown how these limitations can be partially lifted using an iterative transfer matrix approach applied to the EQEPV.
- Subjects
QUANTUM efficiency; CHARGE transfer; ABSORPTION cross sections; PARAMETERIZATION; RECIPROCITY theorems; ELECTRON donors; PHOTOVOLTAIC power systems
- Publication
Advanced Energy Materials, 2020, Vol 10, Issue 41, p1
- ISSN
1614-6832
- Publication type
Article
- DOI
10.1002/aenm.202001828