Insights into the Failure Mechanisms of Organic Photodetectors

Kielar, Marcin; Daanoune, Mehdi; François-Martin, Olivier; Flament, Bruno; Dhez, Olivier; Pandey, Ajay K.; Chambon, Sylvain; Clerc, R.; Hirsch, Lionel

doi:10.1002/aelm.201700526

Cited by 21 publications

(16 citation statements)

References 37 publications

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“…Importantly, the classical boundary conditions introduced by Schottky 29 were used, which consists in keeping the electron and hole concentrations at electrode contacts constant under field and lighting and equal to their equilibrium values. Previous results have shown that these boundary conditions were in good agreement with experiments, accurately predicting the impact of contact work function modification and temperature 37 . Moreover, the HOMO and LUMO effective density of states N 0 was selected according to a common value found in literature 38 to 10 26 m -3 .…”

Section: ) Investigation Of the Main Features Of Gain In Organic Phosupporting

confidence: 67%

“…In presence of light, photo generated electron may remain trapped within the traps, creating negative charges within the active layer of the device. The C n , C p trap parameters are not accurately known, and a large set of value can be found in the literature 37,42 . We decided arbitrary to use the value of 10 -13 cm 3 /s.…”

Section: ) Investigation Of the Main Features Of Gain In Organic Phomentioning

confidence: 99%

“…For a comparison between our model and experimental data, the following field dependent mobility model has been used (assuming same mobility for electrons and holes in agreement with the literature 39 ). µ( ) = µ exp ( √ ) (15) Interestingly, all parameters needed for reproducing experiments were already determined in a previous work 37 , by comparison between simulations and experiments on photodiodes (not photoresistor). No further adjustment was needed to reproduce photoresistor results, except a minor adjustment of the value of the work functions of PEDOT electrodes (around 5.36 eV).…”

Section: ) Experimental Validationmentioning

confidence: 99%

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Physics of trap assisted photomultiplication in vertical organic photoresistors

Daanoune

Clerc

Flament

et al. 2020

Journal of Applied Physics

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Several experimental groups have reported recently an intriguing high level of gain (Photo-Multiplication) in vertical organic photo-resistance (as well as in other technologies, such as perovskite for instance). This mechanism is sometimes named as "Trap-Assisted Photo-Multiplication". This paper investigates the origin of this mechanism by the mean of drift diffusion simulations, analytical theory and experiments, considering the particular case of PCDTBT:PC 60 BM photoresistors, although some conclusions are likely to apply in other technologies. It turns out that an excess of charges (induced by electron-holes carrier generation) may trigger additional carrier injection, leading to photomultiplication, under specific circumstances. We call this mechanism "gain by injection enhancement". Electron (resp. hole) trapping for P only (resp. N only) device can play this role efficiently. As these additional carriers came from contacts, significant dark current injection is thus needed to achieve large value of gain, explaining why this mechanism can occur only in P (or N) only photoresistors (and not photodiodes or intrinsic photoresistor, i.e. with mid gap contacts). In such devices however, the detectivity remains intrinsically limited by the high level of dark injection currents required to get gain, and consequently this type of device may be interesting in particular technologies where it is not possible to achieve low dark currents using photodiodes. However, penalized by the slow traps dynamic, the cut off frequency of these devices remains extremely low (< 100 Hz). Also, this gain takes high value only at low irradiance, making photoresistor responsivity light dependent. All these results bring new light in analysing and optimising photoresistor, opening a large field of investigation to take advantage of gain by injection enhancement.

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Section: ) Investigation Of the Main Features Of Gain In Organic Phosupporting

confidence: 67%

Section: ) Investigation Of the Main Features Of Gain In Organic Phomentioning

confidence: 99%

Section: ) Experimental Validationmentioning

confidence: 99%

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Physics of trap assisted photomultiplication in vertical organic photoresistors

Daanoune

Clerc

Flament

et al. 2020

Journal of Applied Physics

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“…The open‐circuit voltage is however one of the key parameters of organic photovoltaic cells (OPVs), its origin and role in OPV performance have been extensively investigated . That being said, OPVs operate at high illumination intensities (≈100 mW cm −2 ) whereas OPDs tend to function under low irradiance to minimize overall power consumption and degradation mechanisms (such as photooxidation) . It is worth emphasizing that the V oc mode could actually lead to a self‐powered detector.…”

Section: Resultsmentioning

confidence: 99%

Light Detection in Open‐Circuit Voltage Mode of Organic Photodetectors

Kielar

Hamid

Wiemer

et al. 2019

Adv Funct Materials

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Organic photodetectors (OPDs) are promising candidates for next‐generation light sensors as they combine unique material properties with high‐level performance in converting photons into electrical signals. However, low‐level light detection with OPD is often limited by device dark current. Here, the open‐circuit voltage (Voc ) regime of OPDs is shown to be efficient for detecting low light signals (<100 µW cm−2). It is established that the light‐dependence of Voc exhibits two distinct regimes as function of irradiance: linear and logarithmic. Whereas the observed logarithmic regime is well understood in organic photovoltaic cells (OPVs), it is shown experimentally and theoretically that the linear regime is due to the non‐infinite shunt resistance of the OPD device. Overall, OPDs composed of rubrene and fullerene show photovoltage light sensitivity across nine orders of magnitude with a detection limit as low as 400 pW cm−2. A photovoltage responsivity of 1.75 V m2 W−1 demonstrates highly efficient performance without the necessity to supress high dark current. This approach opens up new possibilities for resolving low light signals and provides simplified design rules for OPDs.

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“…We illustrate this concept using a solution processed organic photodiode (OPD). OPDs are currently attracting extensive interest2,3,12–16 due primarily to their compatibility with large‐area, low‐cost production17 onto lightweight flexible substrates, which facilitates applications such as wearable sensors,18,19 smart packaging,20,21 and certain medical technologies 18,22–24. Such devices usually operate under an applied reverse bias,15 and have wavelength sensitivity that can extend from the UV to the near infra‐red (NIR) 25,26.…”

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confidence: 99%

Color Determination from a Single Broadband Organic Photodiode

Dyson

Verhage

et al. 2020

Advanced Optical Materials

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201901722.Obtaining spectral information about incident light, whether a spectrum, a color image, or simply the average wavelength, is highly desirable for many applications such as machine vision and chemical analysis. [1][2][3][4] Such "color information" requires wavelength discrimination and is provided in a conventional spectrometer by a dispersive component such as a prism or diffraction grating. While such components enable high spectral

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Insights into the Failure Mechanisms of Organic Photodetectors

Abstract: This work investigates in details the reliability of the PCDTBT:PC60BM-based

Cited by 21 publications

References 37 publications

Physics of trap assisted photomultiplication in vertical organic photoresistors

Physics of trap assisted photomultiplication in vertical organic photoresistors

Light Detection in Open‐Circuit Voltage Mode of Organic Photodetectors

Color Determination from a Single Broadband Organic Photodiode

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