WP1: This workpackage will produce a description of the most important interfaces in a solar cell (the silver-silicon contacting interface and the silicon-silicon nitride passivating interface) at the atomic scale. These interfacial models can then be used in the project both to understand the interfacial properties (such as the Schottky barrier height for the contacting interface – see WP3 and the importance of using a gradual interface to reduce the population of recombination centres – see WP4) and as starting configurations for other calculations (see WP3, WP4 for details). The socio-economic impact and wider implications of this workpackage are therefore seen in its input to these workpackages, and through them in the design of better solar cells.
WP2: As electronic devices shrink, scattering at defects and interfaces plays an increasing role and an atomistic description becomes important, maybe even mandatory. Hence, classical electronic device simulations, which are usually based on Boltzmann’s transport equation, will be replaced by simulations that take into account the one-electron Schrödinger equation (treating non-interacting electrons) with suitably parameterized weak interactions between electrons and interactions between the electrons and the lattice.
On the other hand, ab-initio (parameter-free) methods aim to solve the true many electron Schrödinger equation (treating strongly interacting electrons). But the solution of the many electron Schrödinger equation is only possible for very small systems.Our efforts contribute to the merger between classical electronic device simulation (aimed at macroscopic models containing billion of atoms) and full ab-initio simulations (aimed at few atoms). It aims to bridge this gap addressing systems and models containing typically 100.000 atoms. If we achieve our goal, we will change the methods used to simulate electronic devices. This might yield new insight in solar cells, but the methods developed here are broadly applicable to other electronic devices and nanostructures.
WP3: A multi-scale modelling framework will be created to describe diffusion processes leading to the metallisation, as well as charge transport at the metal-semiconductor interface. This requires development of a new generic methodology, which can be useful to many different fields in addition to improving contacting schemes for existing solar cells.
WP4: The aim of this workpackage is to calculate principal energy loss mechanisms of photocarriers caused by various defects at the passivation interface of Si/SiNx of Si solar cells by developing a multi-scale first-principles method. By mapping with experimental data of defect generation as a function of device fabrication, we will then be able to understand the energy loss of photocarriers, and thus optimize device performance. The method has been focused on passivation interface of Si/SiNx of Si solar cells. It is however very generic for studying various energy conversion processes in Si-based solar cells as well as other semiconductor solar cells such as quantum dot based ones where multiple exciton generation is expected to enhance significantly the solar energy conversion efficiency.
WP5: The new fundamental insight into the metallisation process gained by modelling will lead to the formulation of improved metal pastes. Since the use of large amounts of expensive silver in the rapidly growing solar cell industry is problematic, new materials for the metallic part will be introduced.
Furthermore, it will be possible to test material systems for contact formation in a modelling environment instead of having to go through very expensive trial-and-error experimental research. This will not only strengthen Europe’s knowledge position in the field of multi-scale modelling but also improve the competitiveness of the European PV industry and generate knowledge to ensure its transformation from a resource-intensive to a knowledge-intensive base.
WP6: We will obtain new fundamental insight into recombination processes at interfaces in solar cells and related semiconductor materials which will enable improved passivation schemes in industrial production.