Influence of static disorder of charge transfer state on voltage loss in organic photovoltaics

Yan, Jun; Rezasoltani, Elham; Azzouzi, Mohammed; Eisner, Flurin; Nelson, Jenny

doi:10.1038/s41467-021-23975-3

Cited by 52 publications

(79 citation statements)

References 70 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since efficient OSCs are based on blended films whose components form clusters of non-rigid donors and acceptors that feature significant inhomogeneous line-broadening, we expect that static disorder is, in fact, important to understand the dynamics of CT states in OSCs. This is in correspondence with the most recent theoretical study by Yan et al [57] and the experimental work by Upreti et al [39] who reinforce not only the claim concerning the importance of static disorder in the description of CT states in OSCs itself but stress its relevance for the open-circuit voltage of CT states.…”

Section: Discussionsupporting

confidence: 90%

Static and Dynamic Disorder of Charge Transfer States Probed by Optical Spectroscopy

Kahle

Rudnick

Wedler

et al. 2022

Advanced Energy Materials

View full text Add to dashboard Cite

Since the key role of charge transfers (CT) states has been identified for organic solar cells (OSCs), research into their properties is a timely topic. Conventionally, their absorption and emission spectra are described in terms of Marcus’ electron transfer theory. This is a single site approach with the essential parameter being the reorganization energy. Thus, it ignores ensemble effects, notably the role of static disorder that is inevitably present in a spin‐coated OSC film. Here time dependent photoluminescence spectroscopy is applied on blends of the polymeric donor MeLPPP with either the non‐fullerene acceptor SF‐PDI2 or with PC61BM within a temperature range from 295 to 5 K. The authors monitor how initially excited singlet states are converted to emissive CT states. Concomitantly, emission from residual singlets on the acceptor is observed rather than hybrid CT‐states. The role of spectral diffusion in this process is discussed. From the temperature and time dependent linewidths of absorption, fluorescence, and CT emission, the static and dynamic contributions to the total disorder are inferred. In both blends, at 295 K, the contribution of static disorder is comparable to the dynamic disorder.

show abstract

Section: Discussionsupporting

confidence: 90%

Static and Dynamic Disorder of Charge Transfer States Probed by Optical Spectroscopy

Kahle

Rudnick

Wedler

et al. 2022

Advanced Energy Materials

View full text Add to dashboard Cite

show abstract

“…The first addition to classical Marcus theory is the explicit consideration of static and quantized dynamic disorder. Even though the exact impact of static disorder on the line-width broadening is still debated [93,94,135], static disorder is likely more relevant for polymer blends, with the many more torsional and conformational degrees of freedom of the molecules, compared to films based on small molecules.…”

Section: Discussion Of Advanced Models For Characterizing Ct States and Voltage Lossesmentioning

confidence: 99%

“…Polymer based solar cells show a range of disorder contributions, e.g. large confirmational and torsional disorder [136], electronic anisotropy, and possible phase aggregation, that are not present in dilute small molecule blends [135]. In multiple accounts, static disorder was found to have a strong impact on extracted CT state parameters and recombination losses for polymer based solar cells [136].…”

Section: Sources Of Spectral Broadening In Different Modelsmentioning

confidence: 97%

“…In contrast, the recently published work by Yan et al criticised that the material systems studied by Tvingstedt and Göhler et al, i.e. dilute donor:fullerene systems, have previously been studied precisely because morphological disorder is minimised [135]. Polymer based solar cells show a range of disorder contributions, e.g.…”

Section: Sources Of Spectral Broadening In Different Modelsmentioning

confidence: 99%

“…In conclusion, future studies of static and dynamic disorder are encouraged to be performed on both small molecule and polymer-based systems. In addition to measuring temperature dependent absorption and emission spectra, experimental and theoretical studies [136] of the interfacial microstructure and phase aggregation are crucial to providing a more complete picture of the possible impact of static disorder on CT state properties [135].…”

Section: Sources Of Spectral Broadening In Different Modelsmentioning

confidence: 99%

See 2 more Smart Citations

Charge transfer state characterization and voltage losses of organic solar cells

2022

View full text Add to dashboard Cite

A correct determination of voltage losses is crucial for the development of organic solar cells with improved performance. This requires an in-depth understanding of the properties of interfacial charge transfer (CT) states, which not only set the upper limit for the open-circuit voltage of a system, but also govern radiative and non-radiative recombination processes. Over the last decade, different approaches have emerged to classify voltage losses in organic solar cells that rely on a generic detailed balance approach or additionally include CT state parameters that are specific to organic solar cells. In the latter case, a correct determination of CT state properties is paramount. In this work, we summarize the different frameworks used today to calculate voltage losses and provide an in-depth discussion of the currently most important models used to characterize CT state properties from absorption and emission data of organic thin films and solar cells. We also address practical concerns during the data recording, analysis, and fitting process. Departing from the classical two-state Marcus theory approach, we discuss the importance of quantized molecular vibrations and energetic hybridization effects in organic donor-acceptor systems with the goal to providing the reader with a detailed understanding of when each model is most appropriate.

show abstract

An Impedance Study of the Density of States Distribution in Blends of PM6:Y6 in Relation to Barrierless Dissociation of CT States

Kroh

Athanasopoulos

Nádaždy

et al. 2023

Adv Funct Materials

View full text Add to dashboard Cite

In an endeavor to understand why the dissociation of charge‐transfer (CT) states in a PM6:Y6 solar‐cell is not a thermally activated process, measurements of energy‐resolved impedance as well as of intrinsic photoconduction are employed. This study determines the density of states distributions of the pertinent HOMO and LUMO states and obtains a Coulomb binding energy (Eb,CT) of ≈150 meV. This is 250 meV lower than the value expected for a pair of localized charges with 1 nm separation. The reason is that the hole is delocalized in the polymer and the electron is shared among Y6 molecules forming a J‐like aggregate. There are two key reasons why this binding energy of the CT state is not reflected in the temperature dependence of the photocurrent of PM6:Y6‐diode: i) The e–h dissociation in a disordered system is a multi‐step process whose activation energy is principally different from the binding energy of the CT state and can be substantially less than Eb,CT, and ii) since dissociation of the CT state competes with its intrinsic decay, the dissociation yield saturates once the rate of dissociation grossly exceeds the rate of intrinsic decay. This study argues that these conditions are met in a PM6:Y6‐solar cell.

show abstract

Influence of static disorder of charge transfer state on voltage loss in organic photovoltaics

Cited by 52 publications

References 70 publications

Static and Dynamic Disorder of Charge Transfer States Probed by Optical Spectroscopy

Static and Dynamic Disorder of Charge Transfer States Probed by Optical Spectroscopy

Charge transfer state characterization and voltage losses of organic solar cells

An Impedance Study of the Density of States Distribution in Blends of PM6:Y6 in Relation to Barrierless Dissociation of CT States

Contact Info

Product

Resources

About