1,721,032 research outputs found
A Review on the Fundamental Properties of Sb2Se3-Based Thin Film Solar Cells
No full textThere has been a recent surge in interest toward thin film-based solar cells, specifically new absorber materials composed by Earth-abundant and non-toxic elements. Among these materials, antimony selenide (Sb2Se3) is a good candidate due to its peculiar properties, such as an appropriate bandgap that promises a theoretical maximum power conversion efficiency of 33% and an absorption coefficient of around 105 cm−1, enabling its use as a thin film absorber layer. However, charge carrier transport has been revealed to be problematic due to its cumbersome structure and the lack of a doping strategy. In this work, we aim to provide a clear picture of the state-of-the-art regarding research on Sb2Se3-based solar cells and its prospects, from the successful achievements to the challenges that are still to be overcome. We also report on the key parameters of antimony selenide with a close focus on the different characteristics associated with films grown from different techniques
Narrowband organic photodetectors - towards miniaturized, spectroscopic sensing
No full textOmnipresent quality monitoring in food products, blood-oxygen measurement in lightweight conformal wrist bands, or data-driven automated industrial production: Innovation in many fields is being empowered by sensor technology. Specifically, organic photodetectors (OPDs) promise great advances due to their beneficial properties and low-cost production. Recent research has led to rapid improvement in all performance parameters of OPDs, which are now on-par or better than their inorganic counterparts, such as silicon or indium gallium arsenide photodetectors, in several aspects. In particular, it is possible to directly design OPDs for specific wavelengths. This makes expensive and bulky optical filters obsolete and allows for miniature detector devices. In this review, recent progress of such narrowband OPDs is systematically summarized covering all aspects from narrow-photo-absorbing materials to device architecture engineering. The recent challenges for narrowband OPDs, like achieving high responsivity, low dark current, high response speed, and good dynamic range are carefully addressed. Finally, application demonstrations covering broadband and narrowband OPDs are discussed. Importantly, several exciting research perspectives, which will stimulate further research on organic-semiconductor-based photodetectors, are pointed out at the very end of this review.BMBF Federal Ministry of Education & Research (BMBF) [16ME0012, 01DR20008A]; German Research Foundation (DFG)German Research Foundation (DFG) [442597684]; Graduate Academy of Technische Universitat Dresden; China Scholarship Council (no. 201706070125
Organic Cavity Photodetectors Based on Nanometer-Thick Active Layers for Tunable Monochromatic Spectral Response
No full textApplication of spectroscopic photodetecting technologies in future innovations such as wearable or integrated electronics will require miniaturized spectrometers. This can be achieved by using an array of small-area, wavelength-selective photodetectors. Here, filterless narrowband photodetectors based on a novel device concept are demonstrated. The narrowband photoresponse is realized by utilizing nanometer-thick 2,24(3,4-dimethy-[2,2:5,2:5,2:5,2-quinquethiophenel-5,5-diyl)bis (methanylylidene))-dimalononitrile (DCV5T-Me): C-60 photoactive layers (3-6 nm) in a Fabry-Perot cavity. By varying the cavity thickness, achieved by adjusting the transport layer thicknesses, we realize continuously tunable detection wavelengths, spanning the entire visible region (400-700 nm). Most importantly, because the active layer is only nanometer-thick, position of the active layer can be adjusted within the cavity. Thus, with an optimized position of the active layer, the photodetectors exhibit an overtone free, monochromatic spectral response with a full-width-at-half-maximum value of 25 nm and an external quantum efficiency over 50%. Although the absorber layers were kept thin, we realize peak specific detectivities over 10(12) Jones, which is comparable to that of the most efficient narrowband organic photodetectors lacking spectral tunability over a broad wavelength range.Z.T. acknowledges a Starting Grant from Donghua University, and Z.M. acknowledges an Alexander-von-Humboldt Fellowship. The work was further supported by the German Federal Ministry for Education and Research (BMBF) through the InnoProfile Projekt "Organische p-i-n Bauelemente 2.2"
Innovative and sustainable solar cells based on abundant elements on the Earth crust
No full textAntimony selenide is a very promising material for photovoltaic applications, with the potential to become a competitive alternative to more traditional silicon, CdTe and CIGS-based technologies. A notable feature of Sb2Se3 is its strong anisotropy, and this property is reflected in the performance parameters of the solar cell. In this study a novel method is explored to control the grain orientation and its effects on the photovoltaic parameters of the solar cells. Furthermore, an innovative approach to create a low-resistivity, Ohmic back-contact is presented, which is crucial for enhancing the efficiency and performance of Sb2Se3-based solar cells
Selectively absorbing small-molecule solar cells for self-powered electrochromic windows
No full textDynamic control of solar transmission by photovoltaic-powered electrochromic smart windows is an up-andcoming approach towards the reduction of energy consumption in buildings. Selectively-absorbing transparent organic solar cells are capable of exhibiting excellent visible-light transparency as well as respectable power conversion efficiencies. This work presents three different transparent small-molecule solar cells (TSCs) with an area of 2.52 cm2, two of which are UV-absorbing and one of which absorbs in the NIR, each in combination with an organic electrochromic device (EC). The NIR-absorbing TSC uses a BDP-OMe:C60 combination, and has a power conversion efficiency of 4% with an average visible light transmission (AVT) of 40%. The two UVharvesting systems, alpha-6T/B4PYMPM and NPB:B4PYMPM, each have an AVT of 50-65%, as well as high opencircuit voltages of 1.5-2.0 V. We demonstrate that these photogenerated voltages are sufficient to power a fluoran dye-based organic EC, which has excellent optical properties: its color ranges from highly transparent to deep black, and its on/off contrast ratio is higher than 80% in the range between 390 nm and 640 nm. Selfpowered smart windows made by the combination of TSCs and ECs provide a way to significantly reduce energy consumption from air conditioning and lighting, towards zero-energy buildings.X.J. thanks support from the China Scholarship Council (no. 201706140127) and Graduate Academy of Technische Universit¨ at Dresden. The authors acknowledge the Free State of Saxony and the
European Regional Development Fund for financial support within the project REAL (100364085)
Reverse dark current in organic photodetectors and the major role of traps as source of noise
No full textOrganic photodetectors have promising applications in low-cost imaging, health monitoring and near-infrared sensing. Recent research on organic photodetectors based on donor-acceptor systems has resulted in narrow-band, flexible and biocompatible devices, of which the best reach external photovoltaic quantum efficiencies approaching 100%. However, the high noise spectral density of these devices limits their specific detectivity to around 10(13)Jones in the visible and several orders of magnitude lower in the near-infrared, severely reducing performance. Here, we show that the shot noise, proportional to the dark current, dominates the noise spectral density, demanding a comprehensive understanding of the dark current. We demonstrate that, in addition to the intrinsic saturation current generated via charge-transfer states, dark current contains a major contribution from trap-assisted generated charges and decreases systematically with decreasing concentration of traps. By modeling the dark current of several donor-acceptor systems, we reveal the interplay between traps and charge-transfer states as source of dark current and show that traps dominate the generation processes, thus being the main limiting factor of organic photodetectors detectivity. The suppression of dark current in organic photodetectors (OPDs) is important for maximizing the performance of the devices. Here, the authors report the relationship between the high dark saturation current and the presence of mid-gap trap states in OPDs with a donor-acceptor structure.Open Access funding enabled and organized by Projekt DEAL.
Acknowledgements
This work was supported by the German Federal Ministry for Education and Research (BMBF) and by the German Research Foundation (DFG) within the Cluster of excellence Center for Advancing Electronics Dresden (cfaed) and the DFG projects HEFOS (Grant No. FI 2449/1-1) and Photogen (Grant No. VA 1035/5-1). B.K.B. acknowledges funding from DFG Priority Programme FFlexCom under the project FlexARTwo (LE 747/52-2 and EL 506/22-2). J.K. acknowledges funding by the Deutsche Akademische Austausch Dienst (DAAD). J.B. thanks for the financing from Sächsische Aufbaubank through project InfraKart (Grant No. 100325708). Furthermore, we acknowledge N. Sergeeva, Prof. Dr. T. Kirchartz, and Prof. Dr. B. E. Pieters for fruitful discussions.Kublitski, J; Hofacker, A (corresponding author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, Nothnitzer Str 61, D-01187 Dresden, Germany ; Tech Univ Dresden, Inst Appl Phys, Nothnitzer Str 61, D-01187 Dresden, Germany.
Vandewal, K (corresponding author), Hasselt Univ, Inst Mat Onderzoek IMO, Wetenschapspk 1, BE-3590 Diepenbeek, Belgium.
[email protected]; [email protected]; [email protected]
Intrinsic Detectivity Limits of Organic Near‐Infrared Photodetectors
No full textOrganic photodetectors (OPDs) with a performance comparable to that of conventional inorganic ones have recently been demonstrated for the visible regime. However, near-infrared photodetection has proven to be challenging and, to date, the true potential of organic semiconductors in this spectral range (800-2500 nm) remains largely unexplored. In this work, it is shown that the main factor limiting the specific detectivity (D*) is non-radiative recombination, which is also known to be the main contributor to open-circuit voltage losses. The relation between open-circuit voltage, dark current, and noise current is demonstrated using four bulk-heterojunction devices based on narrow-gap donor polymers. Their maximum achievableD* is calculated alongside a large set of devices to demonstrate an intrinsic upper limit ofD* as a function of the optical gap. It is concluded that OPDs have the potential to be a useful technology up to 2000 nm, given that high external quantum efficiencies can be maintained at these low photon energies.S.G. and C.K. contributed equally to this work. S.G. and F.V. acknowledge
the Research Foundation – Flanders (FWO Vlaanderen) for granting
them a PhD fellowship. P.V. is a postdoctoral fellow of the FWO. K.V.
and W.M. are grateful for project funding by the FWO (G0D0118N,
G0B2718N, and GOH3816NAUHL) and the European Research Council
(ERC, grant agreement 864625). Hasselt University and IMOMEC
have been partners in the SBO project MIRIS (Monolithic Infrared
Image Sensors), supported by VLAIO (Vlaams Agentschap Innoveren
en Ondernemen). C.K. is recipient of a UKRI EPSRC Doctoral Training
Account studentship. P.M. is a Sêr Cymru II Research Chair and A.A. a
Rising Star Fellow funded through the Welsh Government’s Sêr Cymru II
“Sustainable Advanced Materials” Program (European Regional
Development Fund, Welsh European Funding Office and Swansea
University Strategic Initiative). J.K. acknowledges the German Academic
Exchange Service (DAAD) for the PhD fellowship. J.B. acknowledges the
Sächsische Aufbaubank through project no. 100325708 (Infrakart).Vandewal, K (corresponding author), UHasselt Hasselt Univ, Inst Mat Res IMO, Agoralaan 1,Bldg D, B-3590 Diepenbeek, Belgium ; IMEC, Associated Lab IMOMEC, Wetenschapspk 1, B-3590 Diepenbeek, Belgium.
Armin, A (corresponding author), Swansea Univ, Dept Phys, Singleton Pk, Swansea SA2 8PP, W Glam, Wales.
[email protected]; [email protected]
Stacked Dual-Wavelength Near-Infrared Organic Photodetectors
Full text linkOrganic near-infrared (NIR) detectors have potential applications in biomedicine, agriculture, and manufacturing industries to identify and quantify materials contactless, in real time and at a low cost. Recently, tunable narrow-band NIR sensors based on charge-transfer state absorption of bulk-heterojunctions embedded into Fabry-Perot micro-cavities have been demonstrated. In this work, this type of sensor is further miniaturized by stacking two sub-cavities on top of each other. The resulting three-terminal device detects and distinguishes photons at two specific wavelengths. By varying the thickness of each sub-cavity, the detection ranges of the two sub-sensors are tuned independently between 790 and 1180, and 1020 and 1435 nm, respectively, with full-width-at-half-maxima ranging between 35 and 61 nm. Transfer matrix modeling is employed to select and optimize device architectures with a suppressed cross-talk in the coupled resonator system formed by the sub-cavities, and thus to allow for two distinct resonances. These stacked photodetectors pave the way for highly integrated, bi-signal spectroscopy tunable over a broad NIR range. To demonstrate the application potential, the stacked dual sensor is used to determine the ethanol concentration in a water solution.The authors acknowledge the DFG project VA 1035/5-1 (Photogen) and the Sachsische Aufbaubank through project no. 100325708 (InfraKart). The authors acknowledge Rico Meerheim and Paul Vince for fruitful discussions. Open access funding enabled and organized by Projekt DEAL.Wang, YZ (corresponding author), Tech Univ Dresden, Dresden Integrated Ctr Appl Phys & Photon Mat IAP, Nothnitzer Str 61, D-01187 Dresden, Germany.
Tech Univ Dresden, Inst Appl Phys, Nothnitzer Str 61, D-01187 Dresden, Germany.
Vandewal, K (corresponding author), Hasselt Univ, Inst Mat Res IMO IMOMEC, Wetenschapspk 1, B-3590 Diepenbeek, Belgium.
[email protected]; [email protected]
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