Sub-bandgap absorption in polymer-fullerene solar cells studied by temperature-dependent external quantum efficiency and absorption spectroscopy

Presselt, Martin; Herrmann, F. P.; Shokhovets, S.; Hoppe, Harald; Runge, Erich; Gobsch, G.

doi:10.1016/j.cplett.2012.05.063

Cited by 30 publications

(34 citation statements)

References 39 publications

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“…Furthermore, we see an unstructured absorption between 700 and 900 nm which is most prominent in P3HT-II and -V. This might be caused by amorphous morphology resulting in increased tail absorption. 71 However, interestingly, the most disordered P3HT-IV batch exhibits a lower absorption in this range. A shallow defect state arising e.g.…”

Section: Optical Spectroscopymentioning

confidence: 96%

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Impact of P3HT materials properties and layer architecture on OPV device stability

Meitzner

Faber

Alam

et al. 2019

Solar Energy Materials and Solar Cells

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We report a cooperative study conducted between different laboratories to investigate organic solar cell degradation with respect to P3HT material properties and different solar cell architectures. Various batches of P3HT were collected from different suppliers reflecting commercial availability as well as properties variability. Among the materials properties explicitly considered were the molar mass, dispersity, regio-regularity, impurities by trace metals and intrinsic doping evaluated from radical concentrations. Each of the participating laboratories contributing test devices applied their own layer stack, i.e. their own device architecture and layout. This variation was appreciated as another parameter for evaluation. Even though a large amount of devices failed due to extrinsic degradation effects, indeed, some materials properties were found to be more important than others for obtaining long lifetimes and high stability of P3HT-based polymer solar cells.

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Section: Optical Spectroscopymentioning

confidence: 96%

“…A custom-made setup for photothermal deflection spectroscopy (PDS) was used to determine the sub-bandgap absorption of all investigated P3HT films as done in previous works 69,70,71 . The measurement principle and basic setup of PDS is described elsewhere.…”

Section: Optical Spectroscopy -Ultraviolet/visible-spectroscopy (Uv/vmentioning

confidence: 99%

Impact of P3HT materials properties and layer architecture on OPV device stability

Meitzner

Faber

Alam

et al. 2019

Solar Energy Materials and Solar Cells

Self Cite

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“…With separate DOS distributions, however, it is plausible that the macroscopic mobility would be dominated more so by charge transport within the pure domains containing a Gaussian DOS, as indicated by our measurements on neat P3HT, but that the actual recombination event is governed mainly by the spatial and energetic properties of the interfacial regions containing an exponential DOS, which has been indicated by defect spectroscopy. 41,61 To determine the expected recombination rate in this more complex scenario, we need to consider two separate contributions to the recombination rate, the behavior of the carriers in the pure domains and in the interfacial regions. First, we assume that the majority of the carriers are trapped and that the contribution from free-free recombination is negligible.…”

Section: Effect Of Interfacial Statesmentioning

confidence: 99%

Nongeminate recombination in neat P3HT and P3HT:PCBM blend films

Gorenflot

Heiber

Baumann

et al. 2014

Journal of Applied Physics

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The slow decay of charge carriers in polymer-fullerene blends measured in transient studies has raised a number of questions about the mechanisms of nongeminate recombination in these systems. In an attempt to understand this behavior, we have applied a combination of steady-state and transient photoinduced absorption measurements to compare nongeminate recombination behavior in films of neat poly(3-hexyl thiophene) (P3HT) and P3HT blended with [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). Transient measurements show that carrier recombination in the neat P3HT film exhibits second-order decay with a recombination rate coefficient that is similar to that predicted by Langevin theory. In addition, temperature dependent measurements indicate that neat films exhibit recombination behavior consistent with the Gaussian disorder model. In contrast, the P3HT:PCBM blend films are characterized by a strongly reduced recombination rate and an apparent recombination order greater than two. We then assess a number of previously proposed explanations for this behavior, including phase separation, carrier concentration dependent mobility, non-encounter limited recombination, and interfacial states. In the end, we propose a model in which pure domains with a Gaussian density of states are separated by a mixed phase with an exponential density of states. We find that such a model can explain both the reduced magnitude of the recombination rate and the high order recombination kinetics and, based on the current state of knowledge, is the most consistent with experimental observations.Comment: 9 pages, 4 figures; corrected a few minor typos and grammatical error

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“…2, the EQE spectra decrease upon addition of TCTA (from 8 mg to 25 mg in 1 mL o-DCB) particularly for the absorption tail and PCBM transition in the long wavelength range, indicating that the exciton dissociation at a TCTA/ PCBM abundant heterojunction are not efficient. This is in addition to a lower photoelectron generated by the PCBM transition presenting a decrease at 700 nm in the EQE spectrum [27]. The result suggests that the efficiency improvement induced by the TCTA incorporation arises from energetic properties within the heterojunction, not due to the promotion in light harvesting.…”

Section: Mechanisms Of Energy Laddersmentioning

confidence: 95%

Bridging donor–acceptor energy offset using organic dopants as energy ladders to improve open-circuit voltages in bulk-heterojunction solar cells

Chang

Kuo

Chen

et al. 2014

Organic Electronics

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Sub-bandgap absorption in polymer-fullerene solar cells studied by temperature-dependent external quantum efficiency and absorption spectroscopy

Cited by 30 publications

References 39 publications

Impact of P3HT materials properties and layer architecture on OPV device stability

Impact of P3HT materials properties and layer architecture on OPV device stability

Nongeminate recombination in neat P3HT and P3HT:PCBM blend films

Bridging donor–acceptor energy offset using organic dopants as energy ladders to improve open-circuit voltages in bulk-heterojunction solar cells

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