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Printed electronics including large‐area sensing, wearables, and bioelectronic systems are often limited to simple circuits and hence it remains a major challenge to efficiently store data and perform computational tasks. Memristors can be considered as ideal candidates for both purposes. Herein, an inkjet‐printed memristor is demonstrated, which can serve as a digital information storage device, or as an artificial synapse for neuromorphic circuits. This is achieved by suitable manipulation of the ion species in the active layer of the device. For digital‐type memristor operation resistive switching is dominated by cation movement after an initial electroforming step. It allows the device to be utilized as non‐volatile digital memristor, which offers high endurance over 12 672 switching cycles and high uniformity at low operating voltages. To use the device as an electroforming‐free, interface‐based, analog‐type memristor, anion migration is exploited which leads to volatile resistive switching. An important figure of merits such as short‐term plasticity with close to biological synapse timescales is demonstrated, for facilitation (10–177 ms), augmentation (10s), and potentiation (35 s). Furthermore, the device is thoroughly studied regarding its metaplasticity for memory formation. Last but not least, the inkjet‐printed artificial synapse shows non‐linear signal integration and low‐frequency filtering capabilities, which renders it a good candidate for neuromorphic computing architectures, such as reservoir computing. [ABSTRACT FROM AUTHOR]

The recent development of solution‐processed perovskite thin films over micrometer‐sized textured silicon bottom solar cells enables tandem solar cells with power conversion efficiencies > 30%. Next to improved light harvesting, textured silicon wafers are the industrial standard. To achieve high performance, the open‐circuit voltage losses that occur when fabricating perovskite solar cells over such textures need to be mitigated. This study provides a practical guideline to discriminate and address the voltage losses at the interfaces as well as in the bulk of solution‐processed double cation perovskite thin films using photoluminescence quantum yield measurements. Furthermore, the origin of these losses is investigated via morphological, microstructural, and compositional analysis and present possible mitigation strategies. The guideline will be beneficial for scientists working on randomly textured surfaces and provides a deeper understanding on this timely research topic. [ABSTRACT FROM AUTHOR]

We report the fabrication and optimization of multipass inkjet-printed perovskite solar cells. The presented process allows excellent control of crystallization dynamics and thickness of the perovskite layer. In order to obtain a homogenous perovskite film of large and densely packed crystals on a planar TiO2 electron transport layer we make use of an additional vacuum annealing step. Its beneficial impact was characterized in terms of device performance and laser beam induced current mapping as well as atomic force microscopy. The optimized fabrication methods resulted in power conversion efficiencies up to 11.3% of multipass inkjet printed perovskite solar cells. The spin coated reference devices reached 12.8% power conversion efficiency. With these first results, we advance the field of digital printing techniques for perovskites and demonstrate a major step towards highly efficient, low-cost and less Pb-waste producing perovskite solar cells. [ABSTRACT FROM AUTHOR]

Abstract: For paste-coated Cu(In,Ga)Se2 (CIGS) absorber layers used for thin film solar cells one often gets a residual carbon layer between back contact and absorber layer. We investigate the influence of this layer on the solar cells’ performance with co-evaporated CIGS absorbers and find a beneficial effect. The power conversion efficiencies of thin chalcopyrite absorber layers are often limited by the influence of back contact recombination. It is assumed that the carbon layer between the back contact and the absorber layer helps lower this recombination and allows higher open circuit voltages and thus higher conversion efficiencies. [Copyright &y& Elsevier]

We investigate a process used for the selenisation of particle-based precursors to prepare low-cost Cu(In,Ga)(S,Se)2 (CIGS) solar cells. It is suitable for high throughput with a short optimum selenisation duration of 3-5 min and employs a rapid thermal annealing system with elemental selenium vapour. Homogeneous crack-free Cu(In,Ga)S2 precursor films of up to 1 µm are obtained via doctor blading. The high selenium vapour pressure in the selenisation reaction chamber results in the formation of a compact Cu(In,Ga)(S,Se)2 layer on top of a carbon-rich underlayer. In order to investigate the phase development in the film, the selenisation process was interrupted at different stages and the samples were monitored via XRD and surface-sensitive Raman measurements. We find the formation of a polycrystalline Cu(In,Ga)Se2 phase already after 1 s at the target temperature of 550 °C. Furthermore, the effect of initial precursor thickness on solar cell parameters is discussed. Complete solar cells are prepared by conventional methods, leading to conversion efficiencies well above 8%. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: We investigate three different precursor types for selenisation using a rapid thermal process. Two of the precursor sample types are deposited via non-vacuum methods using particle based precursor inks, and the third precursor type investigated are films that are sputtered from a single ternary Cu–In–Ga target. The rapid thermal process is suitable for high throughput with a short optimum selenisation duration of 5min or less and employs elemental selenium vapour. In order to investigate the phase development in the film, the selenisation process was interrupted at different stages and the samples were monitored via X-ray diffraction and surface-sensitive Raman measurements. We find different growth mechanisms for the investigated precursor types with fast CuInSe2 formation for the highly reactive elemental Cu and In particles and a slower formation of polycrystalline Cu(In,Ga)Se2 for Cu(In,Ga)S2 particle based precursors without the formation of additional phases. For selenisation of the sputtered precursor layers, we find the formation of InSe and In2Se3 during the selenisation temperature ramp up. Using the rapid thermal selenisation process, conversion efficiencies of about 2.9% and 4.0% for the printed and 6.0% for the sputtered precursor layers could be demonstrated. [Copyright &y& Elsevier]