How solar cell efficiency is governed by the αμτ product

Kaienburg, Pascal; Krückemeier, Lisa; Lübke, Dana; Nelson, Jenny; Rau, Uwe; Kirchartz, Thomas

doi:10.1103/physrevresearch.2.023109

Cited by 21 publications

(34 citation statements)

References 67 publications

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“…Mater. 2022, 34,2108132 various kinds of new inorganic transport layer materials have been investigated, including NiO x , [59] MnS, [61] Cu(Cr,Ba)O 2 NCs, [60] CuInS 2 /ZnS QDs [31] and Br-GO GO. [109] However, though the utilization of new transport layer materials have achieved favorable performance, they show a limited effect (with PCE just increase from 10.14% to 10.85%, less than 1%) and thus more efforts are still urgently needed.…”

Section: Performance Variation As a Function Of Transport Layermentioning

confidence: 99%

“…A further prerequisite for high photovoltaic performance is that the absorber material should have a sufficiently high mobility−lifetime product to allow efficient charge extraction before recombination happens. [ 34 ] Depending on the exact device geometry and the presence or absence of electric fields, the mobility lifetime product may be replaced by either the diffusion length or the drift length. [ 82 ] Thus, it is not possible to a priori state a certain minimum mobility or lifetime or even mobility−lifetime product necessary to allow efficient photovoltaic energy conversion.…”

Section: Materials Propertiesmentioning

confidence: 99%

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Quantifying Efficiency Limitations in All‐Inorganic Halide Perovskite Solar Cells

et al. 2022

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Figure 2. a) Accumulated number of related articles as a function of time for the search strings given in the legend taken from ISI Web of Science. Proportion of all-inorganic perovskite solar cells are also shown. b) Relationship between champion efficiencies and the accumulated number of related articles. c) The champion power conversion efficiencies of all-inorganic perovskite solar cells along with years. The devices are classified into 5 groups by the iodine to bromine ratio quantified via the value of x. The efficiencies of hybrid perovskite solar cells are also shown for comparison. The devices with Sn doping process are not shown in the figures, because the bandgap deviates significantly from the intrinsic values. d) The champion efficiency of different all-inorganic perovskite solar cells compared with the SQ limit. The record efficiency of c-Si, GaAs and hybrid perovskite solar cells are shown for comparison.

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Section: Performance Variation As a Function Of Transport Layermentioning

confidence: 99%

Section: Materials Propertiesmentioning

confidence: 99%

Quantifying Efficiency Limitations in All‐Inorganic Halide Perovskite Solar Cells

et al. 2022

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“…Having been employed as one of the initial FoMs to quantify charge collection in photovoltaic devices, the carrier lifetime-mobility product has previously gained much attention. [42][43][44][45] At the same time, it has been argued that this parameter is unsuitable for explaining the FF behavior of organic photovoltaic devices as it does not take into account crucial device parameters such as the device thickness and the internal electric field. [9] Figure 3d supports this argument indicating that for transport-limited devices, τμ on its own is not a proper metric for a comparative analysis of charge transport losses and evaluating device performance.…”

Section: Determination Of Effective Drift and Diffusion Lengthsmentioning

confidence: 99%

Explaining the Fill‐Factor and Photocurrent Losses of Nonfullerene Acceptor‐Based Solar Cells by Probing the Long‐Range Charge Carrier Diffusion and Drift Lengths

Tokmoldin

Vollbrecht

Hosseini

et al. 2021

Advanced Energy Materials

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stability have taken OSC performance to new heights. The emergence of a family of nonfullerene acceptors (NFAs) have delivered a discontinuous advance in cell efficiencies, achieving the efficiency levels of first-generation silicon devices, and with the milestone of 20% now in sight. [1][2][3] Further technological challenges are related to facilitating the manufacturing process, mainly by increasing the active layer thickness, whilst preserving the device performance. [4][5][6] To this end, a straightforward and facile quantification of the charge collection performance and losses in transport-limited solar cells is required. [7][8][9] To generate an external photocurrent, free charges have to be extracted. This process is diffusive or driven by drift, where extraction (mostly) competes with nongeminate recombination of free charges. A manifestation of this competition is the fill-factor FF. Some attention has been previously focused on correlating the FF with the efficiency of charge collection in organic solar cells based on the competition between the free charge extraction and second-order bimolecular recombination. [10] The bimolecular recombination is described via a recombination coefficient which is based on the Langevin expression multiplied by a reduction factor that takes into account processes that suppress the recombination below the Langevin limit. [11] In this picture, the extraction efficiency, as characterized by the ratio of the extraction to recombination rates, Organic solar cells (OSC) nowadays match their inorganic competitors in terms of current production but lag behind with regards to their opencircuit voltage loss and fill-factor, with state-of-the-art OSCs rarely displaying fill-factor of 80% and above. The fill-factor of transport-limited solar cells, including organic photovoltaic devices, is affected by material and devicespecific parameters, whose combination is represented in terms of the established figures of merit, such as θ and α. Herein, it is demonstrated that these figures of merit are closely related to the long-range carrier drift and diffusion lengths. Further, a simple approach is presented to devise these characteristic lengths using steady-state photoconductance measurements. This yields a straightforward way of determining θ and α in complete cells and under operating conditions. This approach is applied to a variety of photovoltaic devices-including the high efficiency nonfullerene acceptor blends-and show that the diffusion length of the free carriers provides a good correlation with the fill-factor. It is, finally, concluded that most state-ofthe-art organic solar cells exhibit a sufficiently large drift length to guarantee efficient charge extraction at short circuit, but that they still suffer from too small diffusion lengths of photogenerated carriers limiting their fill factor.

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“…HB194 and DTDCPB also classify as high opticalgap absorber. Apart from the spectral shape, the strength of absorption directly affects the PV performance potential of a material, [25,26] and strong absorption is cited as one of the reasons for high performance of NFAs. [27] Figure 1b shows the in-plane extinction coefficient relevant for absorption under normal incidence.…”

Section: Vacuum Thermal-evaporated Solar Cellsmentioning

confidence: 99%

Assessing the Photovoltaic Quality of Vacuum‐Thermal Evaporated Organic Semiconductor Blends

et al. 2021

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Vacuum‐thermal evaporation (VTE) is a highly relevant fabrication route for organic solar cells (OSCs), especially on an industrial scale as proven by the commercialization of organic light emitting diode‐based displays. While OSC performance is reported for a range of VTE‐deposited molecules, a comprehensive assessment of donor:acceptor blend properties with respect to their photovoltaic performance is scarce. Here, the organic thin films and solar cells of three select systems are fabricated and ellipsometry, external quantum efficiency with high dynamic range, as well as OTRACE are measured to quantify absorption, voltage losses, and charge carrier mobility. These parameters are key to explain OSC performance and will help to rationalize the performance of other material systems reported in literature as the authors’ methodology is applicable beyond VTE systems. Furthermore, it can help to judge the prospects of new molecules in general. The authors find large differences in the measured values and find that today's VTE OSCs can reach high extinction coefficients, but only moderate mobility and voltage loss compared to their solution‐processed counterparts. What needs to be improved for VTE OSCs is outlined to again catch up with their solution‐processed counterparts in terms of power conversion efficiency.

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How solar cell efficiency is governed by the αμτ product

Cited by 21 publications

References 67 publications

Quantifying Efficiency Limitations in All‐Inorganic Halide Perovskite Solar Cells

Quantifying Efficiency Limitations in All‐Inorganic Halide Perovskite Solar Cells

Explaining the Fill‐Factor and Photocurrent Losses of Nonfullerene Acceptor‐Based Solar Cells by Probing the Long‐Range Charge Carrier Diffusion and Drift Lengths

Assessing the Photovoltaic Quality of Vacuum‐Thermal Evaporated Organic Semiconductor Blends

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