Search

Perovskite solar cells (PSCs) have recently attracted the attention of the scientific community because of the rapid advances in their development. Most of the state-of-the-art devices contain mesoporous titanium dioxide (TiO2) as an electron transport layer. The drawback of such TiO2 layers is that it often needs high temperature sintering at 450–500 °C for 30 min, which slows down the fabrication process and is clearly not compatible with future roll-to-roll (R2R) manufacturing. The aim of this study was to develop low temperature and rapid curing techniques for mesoporous TiO2 thin films, which are compatible with R2R processing and heat-sensitive plastic substrates for PSCs. Several alternative annealing techniques were tested on rigid and flexible substrates, such as UV-ozone (UV/O3) treatment, oxygen plasma treatment (O2 plasma) and Intense Pulsed Light (IPL) sintering and compared to conventional thermal annealing. After each treatment, the mesoporous layers were characterized using Raman spectroscopy, UV–vis spectroscopy, thermogravimetric analysis and scanning electron microscopy. Low temperature sintering techniques were specifically optimized for the mesoporous TiO2 layers and were adapted for the fabrication of PSCs. Sintering process and solar cells manufacturing were optimized for two different device architectures on glass as well as on polyethylene naphthalate (PEN) substrates. Moreover, the maximum temperature of the mesoporous TiO2 layer during the IPL curing process was simulated to better understand the curing process. By employing IPL curing, the processing time for the mesoporous TiO2 layer can be reduced from 30 min to a few seconds without significant loss in the device performance. In particular stabilized PCE of 16% and 12% were obtained using IPL on glass and PEN substrates respectively. This processing route paves the way for future low temperature

Perovskite solar cells (PSCs) have recently attracted the attention of the scientific community because of the rapid advances in their development. Most of the state-of-the-art devices contain mesoporous titanium dioxide (TiO2) as an electron transport layer. The drawback of such TiO2 layers is that it often needs high temperature sintering at 450–500 °C for 30 min, which slows down the fabrication process and is clearly not compatible with future roll-to-roll (R2R) manufacturing. The aim of this study was to develop low temperature and rapid curing techniques for mesoporous TiO2 thin films, which are compatible with R2R processing and heat-sensitive plastic substrates for PSCs. Several alternative annealing techniques were tested on rigid and flexible substrates, such as UV-ozone (UV/O3) treatment, oxygen plasma treatment (O2 plasma) and Intense Pulsed Light (IPL) sintering and compared to conventional thermal annealing. After each treatment, the mesoporous layers were characterized using Raman spectroscopy, UV–vis spectroscopy, thermogravimetric analysis and scanning electron microscopy. Low temperature sintering techniques were specifically optimized for the mesoporous TiO2 layers and were adapted for the fabrication of PSCs. Sintering process and solar cells manufacturing were optimized for two different device architectures on glass as well as on polyethylene naphthalate (PEN) substrates. Moreover, the maximum temperature of the mesoporous TiO2 layer during the IPL curing process was simulated to better understand the curing process. By employing IPL curing, the processing time for the mesoporous TiO2 layer can be reduced from 30 min to a few seconds without significant loss in the device performance. In particular stabilized PCE of 16% and 12% were obtained using IPL on glass and PEN substrates respectively. This processing route paves the way for future low temperature

Perovskite solar cells attract a lot attention as alternative energy sources for the future energy market. With the remarkable lab-scale achievements, the investigations into a high-throughput large-scale production of perovskite devices are now on the agenda. The first step towards mass manufacturing should be a replacement of toxic solvents used in the manufacturing of perovskite layer. In this study, a non-toxic and up-scaling compatible solvent system is developed. The impact of the solvent properties on the perovskite crystallization kinetics has been systematically investigated, which is found to be crucial in controlling the surface coverage and layer crystallinity. By optimizing the processing conditions, a stabilized efficiency of 16.0% is achieved with the developed non-toxic solvent system.

Free-form solar cells expand solar power beyond traditional rectangular geometries. With the flexibility of being installed on objects of daily use, they allow making better use of available space and are expected to bring in new possibilities of generating solar power in the coming future. In addition, their customizable shape can add to the aesthetics of the surroundings. Evidently, free-form solar cells need to be efficient as well. One way to improve their performance is to optimize the metallization patterns for these cells. This work introduces an optimization strategy to optimize the metallization designs of a solar cell such that its performance can be maximized. For the purpose of optimization, we model an existing transparent free-form solar cell design, including front and rear electrode patterns, to validate it against previously published experimental results. The front and rear metallizations of this transparent free-form solar cell are subsequently redesigned using topology optimization. More than 50% improvement in output power is achieved by using topology optimization., Accepted Author Manuscript, Structural Optimization and Mechanics

Free-form solar cells expand solar power beyond traditional rectangular geometries. With the flexibility of being installed on objects of daily use, they allow making better use of available space and are expected to bring in new possibilities of generating solar power in the coming future. In addition, their customizable shape can add to the aesthetics of the surroundings. Evidently, free-form solar cells need to be efficient as well. One way to improve their performance is to optimize the metallization patterns for these cells. This work introduces an optimization strategy to optimize the metallization designs of a solar cell such that its performance can be maximized. For the purpose of optimization, we model an existing transparent free-form solar cell design, including front and rear electrode patterns, to validate it against previously published experimental results. The front and rear metallizations of this transparent free-form solar cell are subsequently redesigned using topology optimization. More than 50% improvement in output power is achieved by using topology optimization., Accepted Author Manuscript, Computational Design and Mechanics

The organic photovoltaics field is maturing and reaching a technology readiness level where the focus is on developing large scale fabrication methods. In this light, fully inkjet printed organic solar cells were demonstrated. Inkjet printing allows direct patterning of all the layers, including the electrodes, offering full freedom of design without the use of masks or structuring by hardware. The semitransparent front and back electrodes consist of PEDOT:PSS and conductive Ag fingers, avoiding the use of ITO. The inkjet printing of six functional layer demonstrated minimal losses in performance as compared to the lab-scale standard, spin coated devices. All-inkjet printed large area (>1 cm2) organic solar cells with power conversion efficiency of 4.1% deposited from environmentally friendly solvents in an air atmosphere are demonstrated for the first time. Organic solar cells were fabricated using industrial scale (512 nozzles) printheads, compatible with R2R technology. To prove the great advantage of inkjet printing as a digital technology allowing freedom of forms and designs, large area organic solar cells with different artistic shapes were demonstrated. Reported results confirm that inkjet printing has high potential for the processing of OPV, allowing quick changes in design as well as the materials., Aerospace Structures & Materials, Aerospace Engineering

The organic photovoltaics field is maturing and reaching a technology readiness level where the focus is on developing large scale fabrication methods. In this light, fully inkjet printed organic solar cells were demonstrated. Inkjet printing allows direct patterning of all the layers, including the electrodes, offering full freedom of design without the use of masks or structuring by hardware. The semitransparent front and back electrodes consist of PEDOT:PSS and conductive Ag fingers, avoiding the use of ITO. The inkjet printing of six functional layer demonstrated minimal losses in performance as compared to the lab-scale standard, spin coated devices. All-inkjet printed large area (>1 cm2) organic solar cells with power conversion efficiency of 4.1% deposited from environmentally friendly solvents in an air atmosphere are demonstrated for the first time. Organic solar cells were fabricated using industrial scale (512 nozzles) printheads, compatible with R2R technology. To prove the great advantage of inkjet printing as a digital technology allowing freedom of forms and designs, large area organic solar cells with different artistic shapes were demonstrated. Reported results confirm that inkjet printing has high potential for the processing of OPV, allowing quick changes in design as well as the materials., Aerospace Structures & Materials, Aerospace Engineering

With the recent developments in secondary ion mass spectrometry (SIMS), it is now possible to obtain molecular depth profiles and 3D molecular images of organic thin films, i.e. SIMS depth profiles where the molecular information of the mass spectrum is retained through the sputtering of the sample. Several approaches have been proposed for "damageless" profiling, including the sputtering with SF5(+) and C60(+) clusters, low energy Cs(+) ions and, more recently, large noble gas clusters (Ar500-5000(+)). In this article, we evaluate the merits of these different approaches for the in depth analysis of organic photovoltaic heterojunctions involving poly(3-hexylthiophene) (P3HT) as the electron donor and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as the acceptor. It is demonstrated that the use of 30 keV C60(3+) and 500 eV Cs(+) (500 eV per atom) leads to strong artifacts for layers in which the fullerene derivative PCBM is involved, related to crosslinking and topography development. In comparison, the profiles obtained using 10 keV Ar1700(+) (∼6 eV per atom) do not indicate any sign of artifacts and reveal fine compositional details in the blends. However, increasing the energy of the Ar cluster beam beyond that value leads to irreversible damage and failure of the molecular depth profiling. The profile qualities, apparent interface widths and sputtering yields are analyzed in detail. On the grounds of these experiments and recent molecular dynamics simulations, the discussion addresses the issues of damage and crater formation induced by the sputtering and the analysis ions in such radiation-sensitive materials, and their effects on the profile quality and the depth resolution. Solutions are proposed to optimize the depth resolution using either large Ar clusters or low energy cesium projectiles for sputtering and/or analysis.

Semitransparent organic solar cells employing solution-processable organic wavelength dependent reflectors of chiral nematic (cholesteric) liquid crystals are demonstrated. The cholesteric liquid crystal (CLC) reflects only in a narrow band of the solar spectrum and remains transparent for the remaining wavelengths. The reflective band is matched to the absorption spectrum of the organic solar cell such that only unabsorbed photons that can contribute to the photocurrent are reflected to pass through the active layer a second time. In this way, the efficiency of semitransparent organic solar cells can be enhanced without significant transparency losses. An efficiency increase of 6% was observed when a CLC reflector with a reflection band of 540–620 nm was used, whereas the transparency of the organic solar cells is only suppressed in the 80 nm narrow bandwidth.

Semitransparent organic solar cells employing solution-processable organic wavelength dependent reflectors of chiral nematic (cholesteric) liquid crystals are demonstrated. The cholesteric liquid crystal (CLC) reflects only in a narrow band of the solar spectrum and remains transparent for the remaining wavelengths. The reflective band is matched to the absorption spectrum of the organic solar cell such that only unabsorbed photons that can contribute to the photocurrent are reflected to pass through the active layer a second time. In this way, the efficiency of semitransparent organic solar cells can be enhanced without significant transparency losses. An efficiency increase of 6% was observed when a CLC reflector with a reflection band of 540–620 nm was used, whereas the transparency of the organic solar cells is only suppressed in the 80 nm narrow bandwidth.