3 research outputs found
Photoconductivity of Quantum Dot Films Towards Third-Generation Solar Cells
No full textColloidal semiconductor nanoparticles, also called quantum dots, have unique opto-electronic properties that make them promising candidates for many applications such as solar cells, light–emitting diodes, lasers, or biological imaging. One of the most interesting features is that the bandgap energy can be tuned by changing the particle size. This allows the design of solar cells with optimized absorption of the solar spectrum, resulting in improved power conversion efficiency. Quantum-dot-based opto-electronic devices require photoconductive nanocrystal assemblies, i.e. assemblies in which charge carrier photogeneration and transport are efficient. However, in assemblies of colloidal quantum dots, both the yield for charge carrier photogeneration and the charge mobility are initially low. This is due to the presence of long (1-2 nanometer), insulating molecules that are present at the surface of the dots for particle stabilization and surface passivation. The goal of this thesis was to produce photoconductive films of quantum dots and to understand the mechanisms governing charge generation, transport and decay in those films. Three options to increase the film photoconductivity were investigated in this thesis: capping removal (Chapter 2), capping exchange with short, organic molecules (Chapter 3, 5 and 6), and capping exchange with short, inorganic molecules (Chapter 4). Mobilities greater than 1 cm2/Vs were achieved in films of CdSe and PbSe quantum dots (Chapter 4 and 5), and in some cases, unity quantum yields of charge carrier photogeneration were attained (Chapter 5). Furthermore, charge extraction from quantum dot layers has been demonstrated with encouraging efficiency (Chapter 2). Those results show that quantum dots fulfill the requirements for use as the active material in solar cells.Department of Chemical EngineeringApplied Science
Invoking ‘Empathy for the Planet’ through Participatory Ecological Storytelling: From Human-Centered to Planet-Centered Design
No full textIn sustainable design and innovation, appreciation of the Planet as an equal stakeholder with humans and businesses continues to rise. Yet a consistent challenge arises in that people have difficulties relating to the nonhuman and interpret the world in terms of human values and experiences. We need more practical tools to stimulate a connection, especially in its affective dimension, to the Planet and to include nonhuman stakeholders in sustainability developments. To anchor Planetary understanding and considerations, we investigate the role of participatory storytelling to stimulate a reappraisal of the needs of nonhuman stakeholders through empathy building. To posit this, we defined empathy for the Planet as a holistic relationship with human and nonhuman stakeholders. We facilitated workshops where design students, design professionals, and business stakeholders could co-create environmental stories using human and nonhuman character personas. We analyzed the personas, stories, and participants’ feedback on the process experience and impact and observed that story creators experienced empathy for the Planet through projecting and blending their own emotions and intents onto the characters. We discuss, therefore, how ecological story co-creation can be a tool for self-reflection, collective sense-making, and the inclusion of the voice of Planetary stakeholders relevant for sustainable design and to drive sustainability engagement in general. This research confirms the role of stories and imagination in creating a bridge to the natural world through new, human and nonhuman, perspectives.</p
A Storytelling Methodology to Facilitate User-Centered Co-Ideation between Scientists and Designers
No full textSuccessful implementation of sustainable innovation requires strong collaborative ecosys-tems. In particular, collaboration between scientific and people-centered expertise (e.g., designers) is essential to bring technical innovation through contextualized, meaningful and attractive experiences. However, in practice, these types of expertise are siloed and struggle to communicate and think together. We present a creative design method based on participatory story building to support collaborative user-centered ideation between technology scientists and designers. The core of the method is a new story creation model, the three-tension framework, that facilitates the exploration of users’ experiences and needs during ideation. To evaluate the method’s effectiveness, we conducted open-ended interviews with participants. We found that the method facilitates the expression of different perspectives and outside-the-box creative thinking. An originality and strength of our method is that it favors the discovery of new issues and pain points—rather than only solutions. This, combined with idea enrichment by multidisciplinary expertise, contributes to generating ideas in a broader range of application areas than usual. Our results indicate that participatory storytelling has the potential to facilitate multidisciplinary collaboration and to bring user-centered thinking to non-design stakeholders in order to envision user needs in future scenarios and new ecosystems.Design for SustainabilityCircular Product Desig
