ALTAFOS - Alternative Akzeptoren für effiziente organische Solarzellen

Due to its enormous potential photovoltaics is one of the most important renewable energy sources and therefore in the focus of many efforts, to develop cost efficient solar cells. In the last years especially organic solar cells (OPV) attracted a lot of attention due to their simple manufacturing, e.g. using roll-to-roll printing and the extremely short energy pay-back time. Industries as well as the research community have spent a lot of time an effort to develop efficient, thin and flexible organic solar cells which can be manufactured with a small environmental food print and at low costs. The leading technology – the so-called polymer-fullerene solar cell (OPV) - has reached an impressive power conversion efficiency of ~11 %. At the same time, this approach has also several disadvantages. Fullerene acceptors can be expensive and they show unfavourable optical properties in the visible and infrared range of the solar spectrum. In polymer-fullerene solar cells several different recombination processes are active leading to low open circuit voltages (Voc) and overall limiting to power conversion efficiency of OPVs which is believed to be limited to about 13 %. Recently so-called non-fullerene-acceptors (NFA) were discovered which could cure some of the disadvantages of state-of-the art organic solar cells. Distinctly smaller losses in the open circuit voltage have been observed and power conversion efficiency >10 % have been reported already. It is the goal of the project ALTAFOS to explore the basic properties and the working principles of this new class of acceptor materials and to give an estimation of the efficiency potential of this new generation of organic solar cells. To do so, we will prepare a set of NFAs, study the properties and test them in solar cells. The gathered data will be used to develop the model for the power conversion efficiency and guidelines for the design of nonfullerene acceptors for OPVs. The acquired knowledge of ALTAFOS will pave the way to organic solar cells with higher power conversion efficiencies (15%+) due to their very low loss in the open circuit voltage and could lead to the final breakthrough of OPV. A success of this technology could have an enormous potential for the reduction of CO2-emission in the energy production because of the energy- and cost-efficient production possibilities of OPV.