This figure schematically illustrates the concept of MUJULIMA and the simplified approach to achieve the general objective by the following three main objectives:
1. Production of multiple junction OPVs
Design and synthesis of innovative photoactive materials as well as novel interlayer materials and their functional performance (molecular weight, polydispersity, crystallinity, morphology with fullerenes, charge carrier mobility, etc.) followed by characterization and optimization in order to produce multiple junction OPVs.
- Innovative photoactive materials will focus on novel donor-acceptor conjugated polymers with sufficient variation in optical band gaps to achieve high efficiencies in single, double and triple junction devices.
- Novel interlayer materials will comprise of organic (e.g. polyelectrolytes) and inorganic (e.g. metal oxides) materials to increase charge selectiveness of the contacts and to adjust the work function to improve the ohmicity of the contact.
These materials will first be tested in single junction OPV cells, measuring the energy conversion efficiencies of the cells and performing stability and lifetime tests. To reach high energy conversion cell efficiencies (17% or higher) needed to achieve high module efficiencies (15% or larger) the new photoactive and interlayer materials will be employed in architectures with double and triple junctions.
2. Better light management
Development of materials for better light management within the module by employing up- and down-converter materials (IR to VIS/NIR and UV to VIS) for enhanced spectral usage of the solar spectrum. This will provide an additional relative efficiency increase of at least 15%. Cost efficient use of materials will be ensured by low cost printing/coating technologies and laser scribing. To achieve the highest possible efficiencies the optimum thickness of the different layers within the multiple junction cells will be predicted by electro-optical modelling. Optical modelling will be used to find the best arrangements of (plasmonic) micro- and nanostructures for improved light incoupling (enhanced absorption).
3. Improvement of lifetime and stability
Improvement of the lifetime and stability of the modules by identifying and remediating the degradation mechanisms at material and stack level (layer/material interfaces) will be achieved by developing accelerated ageing test protocols and by improving the outdoor performance of encapsulation materials using special coatings.