Recently molecular photovoltaics, such as dye sensitized cells (DSCs) and perovskite solar cells (PSCs) have emerged as credible contenders to conventional p-n junction photovoltaics. Their certified power conversion efficiency currently attains 25.5 %, exceeding that of the market leader polycrystalline silicon. This lecture covers the genesis and recent evolution of DSCs and PSCs, describing their operational principles and current performance. DSCs have meanwhile found commercial applications for ambient light harvesting and glazing producing electric power from sunlight. The scale up and pilot production of PSCs are progressing rapidly but there remain challenges that still need to be met to implement PSCs on a large commercial scale. PSCs can produce high photovoltages rendering them attractive for applications in tandem cells, e.g. with silicon and as power source for the generation of fuels from sunlight. Examples to be presented are the solar generation of hydrogen from water and the conversion of CO2 to chemical feedstocks such as ethylene, mimicking natural photosynthesis.

Ligand-functionalised gold nanoparticles, AuNPs, are promising conductive ink materials for printed electronics since they provide good dispersion in organic solvents, long shelf-life at ambient conditions, good printability and electrical conductivity after sintering. However, their mechanical and electrical performance degradation under external mechanical deformation often occurs due to the failure of the stress redistribution at microcracks and pores formed within printed structures, which limits their application for flexible electronics. Here, we employ a thiol-terminated additive as a cohesion enhancer in a gold conductive ink formulation to prevent the formation of microcracks and pores arising from the increased surface energy of nanoparticles during drying and sintering processes. The gold ink formulation with the cohesion enhancer exhibits high electrical conductivity of 5.3´10⁶ S/m and electrical performance stability under mechanical deformation for a single printed layer due to the enhanced cohesion compared to the formulation without the cohesion enhancer, which offers exciting potential for their application in flexible electronics.  

The development of water treatment technology has been spurred by the increasing threat of water scarcity faced by the global population. Various sensors such as pH sensors, dissolved oxygen sensors, biosensors, just to name a few have been developed to aid in water treatment processes such as monitoring and assessing the water quality. The advents of nanomaterial and printed electronic technology have opened up new opportunities for printed flexible electrodes in many fields, one of them is the water treatment technology. One example is the use of printed electrodes and electrochemical impedance spectroscopy (EIS) technique to monitor the health of the water filtration membrane that is used for treating seawater. Electrode is one of the most essential components for analytes detection applications with EIS. However, it remains a challenge to fabricate a compact and functional sensing electrode that can survive under such harsh conditions as seawater is known to be corrosive.  With the advances in printing technology, the fabrication of advanced printed electrode systems with miniature designs and improved sensitivity for electrochemical sensing is made possible. This presentation aims to discuss the several aspects of printed electrodes, namely the (1) design consideration, (2) the fabrication consideration, and (3) measurement consideration for the printed electrodes. The challenges and considerations that will be explained include the material options, multi material printing, adhesion between interfaces, and compatibility of different post-processing techniques.

Inspired by plants systems, such as the Venus flytrap that closes in a few milliseconds under mechanical trigger, and the seedpods that open up under hydration, we developed methods to create multifunctional morphing composites. To achieve morphing and functionality, we control the microstructure of composite materials using magnetic orientation or shear-induced 3D printing. Supported by finite element modelling and experimental tests, the materials created can morph into predicted shapes. Including electrical particles inside the composite, at concentrations close to their percolation, the changes in the electrical conductivity can inform about the change in shape and the triggers that caused it. Indeed, morphing create local compression or extension that modifies the interparticle distance in the electrically conductive network. Specifically, 2 examples will be discussed. In the first one, stiff epoxy laminates are made to snap reversibly under mechanical or magnetic trigger. In the other, stiff 3D printed epoxy composites are able to morph reversibly into several preprogrammed configurations, in response to temperature and mechanical force. Combining the electrical response with the morphing, this strategy can create new kinds of computational materials for applications as sensors or actuators in robotics or aerospace.Inspired by plants systems, such as the Venus flytrap that closes in a few milliseconds under mechanical trigger, and the seedpods that open up under hydration, we developed methods to create multifunctional morphing composites. To achieve morphing and functionality, we control the microstructure of composite materials using magnetic orientation or shear-induced 3D printing. Supported by finite element modelling and experimental tests, the materials created can morph into predicted shapes. Including electrical particles inside the composite, at concentrations close to their percolation, the changes in the electrical conductivity can inform about the change in shape and the triggers that caused it. Indeed, morphing create local compression or extension that modifies the interparticle distance in the electrically conductive network. Specifically, 2 examples will be discussed. In the first one, stiff epoxy laminates are made to snap reversibly under mechanical or magnetic trigger. In the other, stiff 3D printed epoxy composites are able to morph reversibly into several preprogrammed configurations, in response to temperature and mechanical force. Combining the electrical response with the morphing, this strategy can create new kinds of computational materials for applications as sensors or actuators in robotics or aerospace.

Printed electronics has opened up plethora of new opportunities towards low-cost and fast fabrication of flexible electronic components. So far, variety of printing techniques have been used to create different passive electronic components, among which inkjet technique demonstrates promising features like computer-controlled pattern reproduction and high resolution print. Recently, printing of piezoelectric materials has gained interest in both academic and industrial area to fabricate variety of components like sensors, actuators, transducers, and energy harvesting devices. Polyvinylidene difluoride (PVDF) and its copolymers like PVDF-TrFE are a class of piezomatrials that feature both flexibility and good piezoelectric performance. These polymers have semicrystalline nature, which means they are consist of small crystalline domains surrounded by amorphous matrix. PVDF based polymers can crystallize at five different crystalline phases, namely α, β, γ, δ, and ε; however, ferro-, piezo-, and pyroelectric properties of theses polymers only originate from polar phases of β and γ[1]. In this study we investigate how graphene oxide (GO) can increase polar crystalline content of PVDF – TrFE and its influence on piezoelectric, ferroelectric, and dielectric properties. After optimizaton of electronic properties, inkjet printable ink was fabricated from PVDF-TrFE and GO.

Photo-responsive materials are increasingly attracting attention as they can transduce light energy, which allows no contact stimulation with high spatial and temporal control, into mechanical energy¹. Within these materials, Liquid Crystal Elastomers (LCEs) have shown the ability to accomplish large and reversible mechanical actuation under external stimuli. By four-dimensional (4D) printing, the precise programming of the morphology of azobenzene-containing liquid crystalline elastomers (LCEs) that respond to light is possible, achieving high control over the mechanical response. Printing of LCE elements is based on the extrusion of the LCEs precursor through a needle creating forces that align the mesogens along a preferential axis called “director” defined by the needle’s moving direction. In a second phase, the orientation of the mesogens is fixed by photo-polymerization.

Fast mechanical responses have been observed in these 4D printed LCE elements when excited with ultraviolet (UV) light, lifting weights heavier than the LCE element and performing significant work. Both photo-chemical and photo-thermal contributions are recognized, generating forces that can be released by blue light excitation². In this regard, the ability to print light-responsive elements with programmed morphology and mechanical response, and capable of producing considerable work, open future opportunities for implementing remotely triggered mechanical functions in multiple fields, such as soft robotics and engineering.

The expanding market of optoelectronic devices is ever-growing, from LEDs and displays to photovoltaic devices and photodetectors. Conventional device manufacturing requires several physical and/or chemical thin film deposition techniques, which typically require high vacuum and high temperature processes. In addition, masking or photolithography are necessary to define the desired device geometry. In contrast to conventional device manufacturing technologies, innovative fabrication approaches have gained great attention. Technologies such as screen printing and inkjet printing (IJP), which have been used extensively in the graphics art industry, are being used to deposit functional materials. Semiconductor material inks like halide perovskites can be prepared to deposit a wide array of functional materials in the form of precursor inks or nanoparticle colloidal suspensions. IJP is a digital material deposition technology, which means that material can be deposited in any pattern with precision without need for masks. It also allows great control of process parameters and is ideal for fast prototyping while having the potential for scalability. Thus, mass scale and cost-effective production of electronic devices is made possible by leveraging the maturity of IJP. However, despite the great potential of IJP, most applications to functional material deposition have involved organic materials, which are known to be less stable than their inorganic counterparts.

Ub this contribution, IJP is used for the fabrication of halide perovskite layers with and without lead and we also present the architecture of fully inorganic functional devices. The printing and characterization of halide perovskites is presented first, and that of transport layers is presented later. Characterization, including XRD, SEM, and profilometry and optical analysis will proceed layer. Afterwards, the fabrication and device characterization of a heterojunction diode and a full device with perovskite is introduced. Its dark I-V characteristics are presented and compared to their counterpart under illumination.

Thanks to their low-temperature processing on large-area flexible substrates thin-film organic photodetectors (OPDs) are very attractive for a range of large area imaging and sensing applications. The presentation will consist of two parts. In the first part I will focus on better understanding the physical mechanisms that determine the intrinsic limits of the detectivity of OPDs, in particular the dark current in relation to dark injection and charge generation-recombination currents. In the second part  will present  some recent developments  in realizing curved X-ray detectors and -upon integration with OLED displays -  biometric scanners that can accurately image finger-, palm and vein patterns and simultaneously record PPG signals that can be used to monitor health parameters such as heart beat, oxygen saturation and blood pressure, thus demonstrating the advantages of organic photodiodes in high-resolution, flexible large-area photodetectors.

The introduction of new processing technologies and the parallel development of new functional (macro)molecules have provided access to well-defined polymer structures and morphologies at different length scales. These materials, organized from the submicron to the macroscopic, are the basis for the implementation of functional systems and devices with new properties and improved performance, necessary to address the challenges that Society faces.[1,2] In this lecture we will try to show, through different examples developed at the Advanced Manufacturing Laboratory at INMA, how advanced processing of polymeric materials, with emphasis in inkjet printing, help us to walk the way that goes from the molecule to the application.[3-6]

Inkjet printing of metal nanoparticles provides design flexibility, rapid processing and enables the 3D printing of functional electronic devices through co-deposition of multiple materials. A single step multifunctional AM of 3D electronic circuitry is demonstrated using a combination of conductive ink with silver nanoparticles (AgNPs) and dielectric materials within a multi-material jetting-based AM system. However, a lower and anisotropic electrical conductivity of printed AgNPs is observed compared to bulk materials. We employ a combination of electrical resistivity tests, morphological analysis and 3D nanoscale chemical analysis of printed devices using silver nanoparticles to show that the polymer stabiliser tends to concentrate between vertically stacked nanoparticle layers as well as at dielectric/conductive interfaces. Understanding the behaviour of organic residues in printed nanoparticles reveals potential new strategies to improve nanomaterial ink formulations and post-process techniques for functional printed electronics.