Predictive Mechanistic Model for the Electrical Impedance and Intensity-Modulated Photocurrent and Photovoltage Spectroscopic Responses of an Organic Bulk Heterojunction Solar Cell

Set, Ying Ting; Birgersson, Erik; Luther, Joachim

doi:10.1103/physrevapplied.5.054002

Cited by 16 publications

(16 citation statements)

References 46 publications

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“…[3,[8][9] Also drift-diffusion numerical calculations have been reported solving the time-dependent continuity and Poisson's equations under small perturbation of the bias boundary condition at the electrodes. [10][11][12][13] Alternatively, in photo-sensitive samples the current or voltage responses to small light intensity perturbations can be also studied, which are the cases of the intensity modulated photocurrent spectroscopy (IMPS) [14][15][16][17][18][19][20][21][22][23][24][25] and the intensity modulated photovoltage spectroscopy (IMVS), [20][21][26][27][28] respectively. IMVS and IMPS individually characterize the current and voltage responsivities Ψ 𝐽 and Ψ 𝑉 , respectively.…”

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confidence: 99%

“…Thus, the accurate solving of the drift-diffusion equations would possibly be the best resource, requiring the use of numerical methods to reproduce the frequency-dependent signals around the OC steady-state under dc illumination. In the case of LIMIS, or individually IMPS and IMVS, the complete development of the time dependent numeric solutions is still in early phases [10] and such task is beyond the scope of this paper. Instead, the focus is set here on the analytical solution for the particular case of one-sided abrupt p-n junction thin film solar cells.…”

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confidence: 99%

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Analytical model for light modulating impedance spectroscopy (LIMIS) in all-solid-state p-n junction solar cells at open-circuit

Almora

Miravet

Matt

et al. 2020

Applied Physics Letters

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Potentiostatic impedance spectroscopy (IS) is a well stablished characterization technique for elucidating the electric resistivity and capacitive features of materials and devices. In the case of solar cells, by applying a small voltage perturbation the current signal is recorded and the recombination processes and defect distributions are among the typical outcomes in IS studies. In this work a photo-impedance approach, named "light intensity modulated impedance spectroscopy" (LIMIS), is first tested in all-solid-state photovoltaic cells by recording the individual photocurrent (IMPS) and photovoltage (IMVS) responsivity signals due to a small light perturbation at opencircuit (OC), and combining them: LIMIS=IMVS/IMPS. The experimental LIMIS spectra from silicon, organic, and perovskite solar cells are presented and compared with IS. An analysis of the equivalent circuit numerical models for total resistive and capacitive features is discussed. Our theoretical findings show a correction to the lifetimes evaluations by obtaining the total differential resistances and capacitances combining IS and LIMIS measurements. This correction addresses the discrepancies among different techniques, as shown with transient photovoltage. The experimental differences between IS and LIMIS (i) proves the unviability of the superposition principle, (ii) suggest a bias-dependent photo-current correction to the empirical Shockley equation of the steady-state current at different illumination intensities around OC and (iii) are proposed as a potential figure of merit for characterizing performance and stability of solar cells. In addition, new features are reported for the low-frequency capacitance of perovskite solar cells, measured by IS and LIMIS.

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confidence: 99%

mentioning

confidence: 99%

Analytical model for light modulating impedance spectroscopy (LIMIS) in all-solid-state p-n junction solar cells at open-circuit

Almora

Miravet

Matt

et al. 2020

Applied Physics Letters

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“…Moreover, previous works emphasized solving the system of coupled rate equations in the frequency domain to facilitate direct comparisons to experi-ment. 31,43 However, this approach only captures the fundamental Fourier mode of the photocurrent response potentially masking contributions of nonlinearities from traprelated charge recombination over the entire sampling range of frequency (time) scales.…”

Section: ■ Experimental and Theoretical Methodsmentioning

confidence: 99%

Implications of Trap-Assisted Nongeminate Charge Recombination on Time- and Frequency-Domain Photocurrent Degradation Signatures of Organic Solar Cells

et al. 2020

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Charge transport and collection in organic solar cells are heavily influenced by traps which ultimately limit the ability to harvest all photogenerated carriers. We investigate photocurrent responses of organic solar cells subjected to varying degrees of aging from time-and frequency-domain perspectives. Intensitymodulated photocurrent spectroscopy (IMPS) is primarily used here to resolve the effect of trap-assisted nongeminate charge recombination over a broad frequency range (e.g., ∼1 mHz−1 MHz). We use a combination of IMPS and time-dependent photocurrent transients to understand characteristic degradation signatures (i.e., positive, low-frequency imaginary component and "gain peak" where the real photocurrent exhibits a characteristic maximum, I max , at high frequencies) unique to organic solar cells. As trap densities and occupation increase with aging and light intensity, the photocurrent contrast (i.e., maximum/steady-state photocurrent, I max /I DC ) and the size of the low-frequency imaginary contribution increase. Substantial harmonic content underlies this trend which becomes more prominent as modulation frequencies and trap levels increase. We then use drift-diffusion simulations to describe IMPS responses and photocurrent transient signals over the entire frequency sampling window for aged devices that show excellent agreement with experiment. The results provide deeper insights into trap-related phenomena over a larger frequency bandwidth and further demonstrate the effectiveness of IMPS in its ability to identify mechanistic and kinetic details of degradation.

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“…Despite the simple concept -measuring the electrical current passing through the sample at various frequencies of the excitation voltage -this technique is currently applied in numerous domains. For example, EIS is commonly used as a testing technique for modern electronic devices: from semiconductor hetero-structures [8] to audiophile amplifiers [9]; EIS is a state-of-the-art method in electrochemistry and materials science: from nano-objects investigation and alternative energy sources characterization to Mars surface research [10,11,12,13,14,15]. Being a label-free non-optical non-destructive and easy to implement technique, EIS became a promising experimental approach in biological and medical applications, such as biosensing technologies [6,16,17,18,19,20] and diagnosis of diseases, including cancer and virus detection [21,22,23,24,25,26,27,28,29,30,31,32].…”

Section: Introductionmentioning

confidence: 99%

Bio-Impedance Spectroscopy: Basics and Applications

Stupin¹,

Kuzina²,

Abelit³

et al. 2020

Preprint

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In this review, we aim to introduce the reader to the technique of electrical impedance spectroscopy (EIS) with a focus on its biological and medical applications. We explain the theoretical and experimental aspects of the EIS with the details essential for biological studies, i.e. interaction of metal electrodes with biological matter and liquids, strategies of increasing measurement rate and noise reduction in bio-EIS experiments etc. We give various examples of successful bio-EIS practical implementations in science and technology: from the whole-body health monitoring and sensors for vision prosthetic care to single living cell examination platforms and virus diseases research. Present review can be used as a bio-EIS tutorial for students as well as a handbook for scientists and engineers due to extensive references covering the contemporary research papers in the field.

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Predictive Mechanistic Model for the Electrical Impedance and Intensity-Modulated Photocurrent and Photovoltage Spectroscopic Responses of an Organic Bulk Heterojunction Solar Cell

Cited by 16 publications

References 46 publications

Analytical model for light modulating impedance spectroscopy (LIMIS) in all-solid-state p-n junction solar cells at open-circuit

Analytical model for light modulating impedance spectroscopy (LIMIS) in all-solid-state p-n junction solar cells at open-circuit

Implications of Trap-Assisted Nongeminate Charge Recombination on Time- and Frequency-Domain Photocurrent Degradation Signatures of Organic Solar Cells

Bio-Impedance Spectroscopy: Basics and Applications

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