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17 december 2018

Approved FOM programme

Number 130.
Title Next generation organic photovoltaics (NGOPV)
Executive organisational unit BUW
Programme management Prof.dr. J.C. Hummelen
Duration 2011-2021
Cost estimate M€ 5.2 (FOM part)

The Focus Group Next generation organic photovoltaics will work on enabling and realizing the next generation of Organic Photovoltaics (OPV) through the development of OPV science. It is based on a multidisciplinary approach where physics, photophysics, device physics, organic chemistry, material science, and theoretical modeling are combined synergistically. The goal of the research programme is to enable PV technologies within the next 10 years that lead to mass production that fits in the accepted roadmap for solar technology. Performance targets are: green technology, >15% efficiency, >20 years lifetime, < 0.25€/Wp.

Background, relevance and implementation
Solution-processed OPV cells are promising low-cost alternatives to conventional silicon-based PV devices. The fabrication of these devices by processing the photoactive layer from solution is the key advantage, enabling cheap, flexible, large-area PV technologies. In the last few years the design and synthesis of new p-type polymers has dramatically improved the power con­version efficiency, presently reaching 8,3% (in laboratory-scale experiments).

At the heart of an OPV device is the interface between the donor and acceptor, where light is converted to free charges, and where the biggest challenges lie. Several basic questions about the mechanism of photoinduced charge-separation across this interface have remained unans­wered, largely because the physical phenomena cannot be studied without the close collabora­tion of materials chemists and device physicists; OPV is truly a multi-disciplinary challenge. Thus, it is through the close collaboration of the three lines of research ‑ theoretical aspects & modeling, physical characterization & device physics, and material development ‑ that this elusive and challenging problem will be tackled and that a complete physical understanding of the microscopic details of charge-separation will be realized.

The key to this programme's approach that will convert the fundamental physics into deliver­able innovations in OPV is to address a fundamental difference between inorganic and organic materials: dielectric properties. The high dielectric constant of inorganic materials screens charges, facilitating their spatial separation after the absorption of light. Organic materials for OPV have thus far almost exclusively used hydrocarbon chains, leading to low dielectric con­stants and tightly-bound charges. This programme blends the discovery of the underlying physics of charge-separation with a radical change in thinking about the materials that is based on simple and well-understood principles. Understanding how dipoles interact to influence the local environment at the nanostructured interfaces between two organic mate­rials is a challenging theoretical problem. Measuring it is a challenging physics problem.

Designing the materials is a challenging chemistry problem. Translating these gains at the charge-separation interface into external efficiency is a multidisciplinary problem rooted in device physics.

A natural outcome of moving away from low-dielectric materials are new materials that are less hydrophobic and can be processed from renewable solvents such as methanol. This move towards 'green' materials for OPV is as important for the long-term impact of OPV technology as efficiency. It brings down the costs associated with scaling and technology transfer and truly sets OPV apart from other technologies as a sustainable means to generate electricity.

Implementation of the scientific results takes place through collaboration with national knowledge institutes (Holst Centre, ECN) for upscaling of OPV fabrication and with the leading OPV industries towards mass production.

This programme was launched following a national call for proposals for FOM focusgroups for fundamental energy research and forms part of and is scientifically connected to the Dutch Institute for Fundamental Energy Research (DIFFER).

During the second half of 2015 the scientific programme of this focus group will be subject to a mid-term evaluation. The final evaluation will consist of a self-evaluation initiated by the programme leader and is foreseen for 2021.

Please find a research highlight that was achieved in 2014 within this FOM programme here.