Understanding the low voltage losses in high-performance non-fullerene acceptor-based organic solar cells

Hofinger, Jakob; Putz, Christoph; Mayr, Felix; Gugujonovic, Katarina; Wielend, Dominik; Scharber, Markus C.

doi:10.1039/d1ma00293g

Cited by 31 publications

(43 citation statements)

References 38 publications

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“…Furthermore, the sub-bandgap behavior of the solar cell does not show any additional CT state absorption features, as often reported for fullerene-based solar cells. 9,38 …”

Section: Resultsmentioning

confidence: 99%

“…It should be noted that we recently have investigated the high-performance D/A system D18:Y6 (EQE PV > 80%), which showed a moderate PL reduction of almost 10% when measured at I SC conditions. 9 Bias-dependent PL measurements of an efficient D18:Y6 solar cell are presented in Fig. S11, ESI.…”

Section: Discussionmentioning

confidence: 99%

“…For solar cells with a prominent CT state absorption and emission, the equations above can be used to fit the low energy CT absorption and high energy CT emission behavior as shown for D18:PC 71 BM. 9 In this case the crossing point E 0-0 can be identified as the CT state energy E CT . As shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…A detailed description of the V OC loss analysis is discussed in our recent publication, where we used the V OC loss analysis to compare the non-radiative voltage losses of high-performance fullerene (D18:PC 71 BM) and non-fullerene (D18:Y6) solar cells. 9 The results of the voltage loss analysis for the two organic solar cells are summarized in Table 1 , revealing that the high-performance NFA-based solar cell exhibits significantly lower non-radiative voltage losses (∼0.2 V) compared to its fullerene-based counterpart (∼0.3 V). Nevertheless, the typically observed non-radiative voltage losses of high-performance NFA-based solar cells around 0.2 V are considerably larger than the 0.03 V or 0.06 V observed for top-end GaAs and perovskite solar cells, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…To evaluate the performance of the newly synthesized acceptor, the photovoltaic parameters and the determined voltage losses of D18:PMI-FF-PMI cells were compared to those of state-of-the-art fullerene (D18:PC 71 BM) and non-fullerene (D18:Y6) solar cells. 9 …”

Section: Introductionmentioning

confidence: 99%

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Wide-bandgap organic solar cells with a novel perylene-based non-fullerene acceptor enabling open-circuit voltages beyond 1.4 V

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“…Furthermore, the sub-bandgap behavior of the solar cell does not show any additional CT state absorption features, as often reported for fullerene-based solar cells. 9,38 …”

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Wide-bandgap organic solar cells with a novel perylene-based non-fullerene acceptor enabling open-circuit voltages beyond 1.4 V

et al. 2022

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Triplet Excitons and Associated Efficiency‐Limiting Pathways in Organic Solar Cell Blends Based on (Non‐) Halogenated PBDB‐T and Y‐Series

Grüne

Londi

Gillett

et al. 2023

Adv Funct Materials

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The great progress in organic photovoltaics (OPV) over the past few years has been largely achieved by the development of non‐fullerene acceptors (NFAs), with power conversion efficiencies now approaching 20%. To further improve device performance, loss mechanisms must be identified and minimized. Triplet states are known to adversely affect device performance, since they can form energetically trapped excitons on low‐lying states that are responsible for non‐radiative losses or even device degradation. Halogenation of OPV materials has long been employed to tailor energy levels and to enhance open circuit voltage. Yet, the influence on recombination to triplet excitons has been largely unexplored. Using the complementary spin‐sensitive methods of photoluminescence detected magnetic resonance and transient electron paramagnetic resonance corroborated by transient absorption and quantum‐chemical calculations, exciton pathways in OPV blends are unravelled employing the polymer donors PBDB‐T, PM6, and PM7 together with NFAs Y6 and Y7. All blends reveal triplet excitons on the NFA populated via non‐geminate hole back transfer and, in blends with halogenated donors, also by spin‐orbit coupling driven intersystem crossing. Identifying these triplet formation pathways in all tested solar cell absorber films highlights the untapped potential for improved charge generation to further increase plateauing OPV efficiencies.

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Determination of Free Charge Carrier Luminescence and Quasi‐Fermi Level Separation in Organic Solar Cells via Transient Photoluminescence Measurements

List

Faisst

Heinz

et al. 2023

Advanced Optical Materials

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The detection of photoluminescence (PL) is extremely valuable for photovoltaic technologies as it provides direct information about the free charge carrier densities and therefore about the separation of the quasi‐Fermi levels (ΔEF). However, for organic solar cells the PL is strongly dominated by photogenerated excitons that in part decay radiatively before they form free charge carriers via dissociation at a donor/acceptor interface. For this reason, it is impossible to deduce the free charge carrier densities and ΔEF directly from the PL signal. To overcome this severe limitation, a new approach is developed that allows disentangling the luminescence of photogenerated excitons from the one of free charge carriers. Due to the large difference in respective lifetimes—for photogenerated excitons it is ≤ ns whereas for free charge carriers it is in the µs‐range—this is achieved by time‐resolved PL measurements. For highly efficient organic solar cells, it is found that ΔEF determined from these PL transients matches perfectly with the electrical voltage. Moreover, the new method also allows for the determination of ΔEF from mere absorber films without electrodes and thus paves the way for a better understanding of organic solar cells.

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Understanding the low voltage losses in high-performance non-fullerene acceptor-based organic solar cells

Abstract: Despite the rapid increase in power conversion efficiency (PCE) of non-fullerene acceptor (NFA) based solar cells in recent years, organic photovoltaic (OPV) devices exhibit considerably larger voltage losses compared to...

Cited by 31 publications

References 38 publications

Wide-bandgap organic solar cells with a novel perylene-based non-fullerene acceptor enabling open-circuit voltages beyond 1.4 V

Wide-bandgap organic solar cells with a novel perylene-based non-fullerene acceptor enabling open-circuit voltages beyond 1.4 V

Triplet Excitons and Associated Efficiency‐Limiting Pathways in Organic Solar Cell Blends Based on (Non‐) Halogenated PBDB‐T and Y‐Series

Determination of Free Charge Carrier Luminescence and Quasi‐Fermi Level Separation in Organic Solar Cells via Transient Photoluminescence Measurements

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