Understanding the Light‐Intensity Dependence of the Short‐Circuit Current of Organic Solar Cells

Hartnagel, Paula; Kirchartz, Thomas

doi:10.1002/adts.202000116

Cited by 56 publications

(58 citation statements)

References 70 publications

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“…This behavior of the recombination rate coincides with what has been observed for band‐to‐band recombination in previous studies. [ 70,71 ] As a result, the recombination rate in the case of ε r = 10 5 is almost homogeneous at 10 suns. On the other hand, in the case of ε r = 3.8, the recombination rate starts to scale superlinearly with light intensity Φ in the low‐field region quickly surpassing the recombination rate at the contacts.…”

Section: Resultsmentioning

confidence: 96%

“…In previous studies, it was already observed that the resulting low‐field region in proximity of the illuminated contact is more pronounced for Urbach tails with higher characteristic energy. [ 43,71 ] Hence, a thorough analysis of the photo‐induced space‐charge effect on the performance of organic solar cells with different Urbach energies under consideration of the illumination condition is required.…”

Section: Resultsmentioning

confidence: 99%

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The Influence of Photo‐Induced Space Charge and Energetic Disorder on the Indoor and Outdoor Performance of Organic Solar Cells

Beuel

Hartnagel

Kirchartz

2021

Advcd Theory and Sims

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Apart from traditional large‐scale outdoor application, organic solar cells are also of interest for powering small, off‐grid electronic devices indoors. For operation under the low light intensities that are typical for indoor application, a high shunt resistance is required calling for thick active layers in industrial processing to ensure maximum coverage. However, the thickness of an organic solar cell based on energetically disordered semiconductors is limited by space‐charge effects from charged shallow defects under nonuniform generation. While other sources of space charge such as doping and asymmetric transport have been extensively discussed in previous studies, this work offers a theoretical analysis of this photo‐induced space charge in shallow defects and visualizes how the space charge builds up with increasing light intensity with drift‐diffusion simulations. It is shown that the effect particularly deteriorates the performance of an organic solar cell with high active‐layer thickness and substantial energetic disorder. However, the simulations reveal that solar cells are less sensitive to these parameters under low light intensities due to a reduced density of photo‐induced space charge. Therefore, a wider range of material systems and absorber thicknesses can be viable for indoor applications than one may initially expect from testing under 1 sun illumination.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

The Influence of Photo‐Induced Space Charge and Energetic Disorder on the Indoor and Outdoor Performance of Organic Solar Cells

Beuel

Hartnagel

Kirchartz

2021

Advcd Theory and Sims

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“…A linear dependence was observed when the value of S1 close to 1 indicates weak bimolecular recombination. Conversely, a value of S1 smaller than 1 suggests that bimolecular recombination of free charge carriers can limit the photocurrent devices [45]. Figs.…”

Section: Resultsmentioning

confidence: 98%

Photostability Study of Inverted Polymer Solar Cells Under AM 1.5G and LED Illumination via Impedance Spectroscopy

Torimtubun¹,

Sánchez²,

Pallarès³

et al. 2021

IEEE J. Electron Devices Soc.

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“…[70] However, this typically only affects J sc values measured at intensities around one sun and higher while there should be no non-linearities at the low light intensities relevant for indoor applications. [71,72] Figure 2c, the quantum efficiency normalized to the maximal spectral irradiance and the resulting integrated short circuit current densities are shown for an organic solar cell with PBDB-TF-T1:BTP-4F-12 (PBDB-TF-T1:Y12) as the absorber material fabricated in our group, which was first shown in ref. [73].…”

Section: Adjusting the Output Power And Visualization Of The Methodsmentioning

confidence: 99%

“…[ 70 ] However, this typically only affects J sc values measured at intensities around one sun and higher while there should be no non‐linearities at the low light intensities relevant for indoor applications. [ 71,72 ]…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Comparing and Quantifying Indoor Performance of Organic Solar Cells

Lübke

Hartnagel

Angona

et al. 2021

Advanced Energy Materials

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An important application that benefits from the tuneability of band gaps in molecular semiconductors is the use of organic photovoltaics (OPV) for indoor light harvesting. The market of the internet of things (IoT) is emerging remarkably and demands to drive high amounts of off-grid low power consumption devices. [8][9][10][11][12][13] The possibility to produce solution-based, lowcost, and flexible solar foils makes OPV a good candidate to fulfill this demand. Furthermore, the absorption spectra of the active materials can be tuned chemically to match different light sources.Although efficiencies for indoor organic photovoltaics (iOPV) and other emerging indoor photovoltaics (iPV) technologies such as halide perovskites [36][37][38][39][40][41][42][43] or dye-sensitized solar cells [44][45][46][47][48][49][50] have improved substantially, it is hard to quantify progress and determine champion solar cells due to a lack of standardized comparison methods. [12,51,52] Different authors use different conditions to evaluate the performance of their devices. The set-ups differ in the illuminance value (ranging typically from 200 to 1000 lux) and the source of light, namely light emitting diodes (LED) or fluorescent lamps (FL) with varying emission spectra and color temperatures. This makes it difficult to compare devices and regularly leads to the publication of tables or figures where data is compared for different input spectra and illuminances. [43,53,54] The exact spectrum and intensity are, however, more than just a minor inconvenience for data comparison but can have a major impact on the output power at a given illuminance and the efficiency. This is due to several reasons. First, the presence of shunts [55][56][57] can have a substantial effect on the dependence of open-circuit voltage and fill factor on the light intensity under indoor conditions. [55,56,58] Second, the short-circuit current at a given illuminance strongly depends on the overlap of the materials' absorption spectra and the spectral emission power of the light source. [53,59] The exact spectrum is even more critical than for outdoor illumination, because indoor light sources have much more narrow spectra with strong emission between wavelengths of 400 and 700 nm [60,61] as compared to the air mass 1.5 global (AM1.5G) spectrum.In the worst-case scenario, an otherwise well-performing solar cell could exhibit low efficiencies if the color temperature of the light source is not suitable to the specific absorber bandgap. Standardizing indoor spectra as done for outdoor efficiency measurements is not practical given the substantial spectral differences between the used light sources. Furthermore, With increasing efficiencies of non-fullerene acceptor-based organic solar cells, thin-film technology is becoming a promising candidate for indoor light harvesting applications. However, the lack of standardized comparison methods makes it difficult to quantify progress and to compare indoor performance. Herein, a simple method to calculate the efficiency ...

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Understanding the Light‐Intensity Dependence of the Short‐Circuit Current of Organic Solar Cells

Cited by 56 publications

References 70 publications

The Influence of Photo‐Induced Space Charge and Energetic Disorder on the Indoor and Outdoor Performance of Organic Solar Cells

The Influence of Photo‐Induced Space Charge and Energetic Disorder on the Indoor and Outdoor Performance of Organic Solar Cells

Photostability Study of Inverted Polymer Solar Cells Under AM 1.5G and LED Illumination via Impedance Spectroscopy

Comparing and Quantifying Indoor Performance of Organic Solar Cells

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