We investigate bulk heterojunction organic photodetectors with unbalanced charge carrier mobilities in the active layer. We present an experimental example of an organic photodetector with external quantum efficiency exceeding 75% (at illumination 638 nm), and bandwidth over 1 MHz, utilizing a 50 nm thick active layer with electron mobility ≈ 10−4 −10−3 cm2/(Vs) and low hole mobility ≈ 5 × 10−7 cm2/(Vs). The presented drift-diffusion simulation of bulk heterojunction photodiodes with Langevin recombination indicates that the bandwidth of photodiode is approximately independent of the mobility of slower charge carriers in the blend. 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. Moreover, when optimizing the bandwidth of bulk heterojunction photodetectors, attention should be focused on the semiconductor with higher mobility.
Active layers of bulk heterojunction are extensively studied because of their great potential for application in low-cost optoelectronic devices like photovoiltaic cells and photodiodes. The performance of such devices is strongly influenced by the formed nanostructures which determine the transport ability of the organic composite. We investigated the charge carrier transport properties of two organic composites: poly(3-hexyothiophene) (P3HT) with (6,6)-phenyl-C60-butyric acid methyl ester (60PCBM)and poly(triarylamine) (PTTA) blended with 60PCBM. The optimised organic blend was used as a matrix material for Cu-In-Se nanocrystals. Adding Cu–In–Se nanocrystals to a P3HT/60PCBM bulk heterojunction leads to a significant improvement of the maximum external quantum efficiency of the investigated system from 48% to 70% (at wavelength 520 nm).
Several applications of the thermoluminescence (TL) technique for investigations of mechanisms of charge carrier
trapping and recombination in electroluminescent polymers which are used for construction of various opto-electronic
devices are described. The presented TL studies were focused on polymers emitting blue light, because such emissive
materials are requested to realize the white-light-emitting OLEDs or RGB-displays. We have investigated wide band-gap
conjugated polymers and also non-conjugated polymers: series of polyfluorenes (homo- and copolymers) and poly(9-
vinylcarbazole), neat and doped with low-molecular-weight dopants. The dopants were introduced in order to improve
the charge carrier transport and also the to modify the recombination processes.
It is shown, that the spectrally resolved thermoluminescence studies, especially when performed in a broad
temperature range allow to characterise the nature of the trapping sites and of the recombination centres and to identify
the mechanisms responsible for transfer of energy in the investigated materials.
Conference Committee Involvement (2)
Advanced Manufacturing Technologies for Micro- and Nanosystems in Security and Defence II
9 September 2019 | Strasbourg, France
Advanced Manufacturing Technologies for Micro- and Nanosystems in Security and Defence
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