Organic Photovoltaics Based on Solution‐Processable Nanostructured Materials: Device Physics and Modeling

Szymański, Marek Zdzisław; Luszczynska, Beata

doi:10.1002/9783527813872.ch9

Cited by 2 publications

(1 citation statement)

References 105 publications

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“…In order to generalize our measurements and to further investigate the influence of unbalanced mobilities on performance of organic photodiodes, we run drift-diffusion simulations of photodiode devices using oedes open-source simulator [36,37]. We use a bulk heterojunction model with Langevin recombination.…”

Section: Device Simulationmentioning

confidence: 99%

Organic bulk heterojunction photodetectors based on polymer blends with unbalanced mobilities

Yong

Luszczynska

Szymański

2020

Semicond. Sci. Technol.

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We investigate bulk heterojunction organic photodetectors with unbalanced charge carrier mobilities in the active layer. We present an experimental example of an organic photodiode with very unbalanced mobilities but achieving state-of-the-art parameters in terms of external quantum efficiency exceeding 75% (at illumination 638 nm), and of bandwidth exceeding 1 MHz. The active layer of the photodiode is a 50 nm thick bulk heterojunction made of a blend of PCBM and copolymer of 5,6-difluoro2,1,3-benzothiadiazole, with mobility of slower charge carriers of order of 5 × 10 −7 cm 2 (Vs) −1 , estimated using space-charge-limited photocurrent technique. To understand why such a low mobility does not have deteriorating effects on the photodetecting performance of the photodiode, we performed drift-diffusion simulations of bulk heterojunction photodiodes with Langevin recombination. According to the simulation, the bandwidth of the photodiode is approximately independent of the mobility of slower charge carriers in the blend, and the negative effect of low mobility on the responsivity can be compensated by increasing the reverse bias. Our study shows that well-performing organic photodetectors can be fabricated using organic semiconductors having too low mobility for photovoltaic applications.

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Section: Device Simulationmentioning

confidence: 99%

Organic bulk heterojunction photodetectors based on polymer blends with unbalanced mobilities

Yong

Luszczynska

Szymański

2020

Semicond. Sci. Technol.

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Scrutinizing thermally stimulated current transients originating from trapped charges in organic semiconductors: A drift-diffusion study

Vael

Jenatsch

Züfle

et al. 2022

Journal of Applied Physics

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Thermally stimulated current (TSC) is a widely used technique to assess trap states and extract their density, energy, and capture rate using analytical expressions. In many cases, the latter are derived from physical models pertaining to inorganic semiconductors stipulating the absence of space charge or constant lifetime of free charge carriers. Especially for organic semiconductors, the validity of these equations can, therefore, be argued. Here, we investigate the validity range of this approach by fitting the classical equations to synthetic TSC data obtained from drift-diffusion simulation using representative input parameters for organic semiconductors. We find that the equation derived for slow recapture rate as well as the initial rise method provide excellent trap parameter predictions. On the other hand, the equation using the temperature of the peak current as well as the one derived for fast retrapping have a limited range of validity. An important merit of drift-diffusion modeling is the possibility to access local variables such as charge carrier density, electric field, and recombinaton. We unravel that a small fraction of traps nearby the electrode cannot be emptied even at high temperature due to the diffusion of charge carriers from the electrode into the semiconductor. Additionally, we find that an important electrostatic factor relates the extracted charge carriers measured by the external circuit and the input trap density. For the homogeneously distributed trap states used here, this factor is precisely two. Finally, extensions of the model are analyzed by implementing temperature and field dependent mobility into the drift-diffusion model.

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Organic Photovoltaics Based on Solution‐Processable Nanostructured Materials: Device Physics and Modeling

Cited by 2 publications

References 105 publications

Organic bulk heterojunction photodetectors based on polymer blends with unbalanced mobilities

Organic bulk heterojunction photodetectors based on polymer blends with unbalanced mobilities

Scrutinizing thermally stimulated current transients originating from trapped charges in organic semiconductors: A drift-diffusion study

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