A crucial challenge for a useful MOST system is to acquire a satisfactory high energy storage density (if possible, higher than 300 kJ/kg). Another challenge of a MOST system is that light can be harvested in the visible region. The functionalization of the NBD with the donor and acceptor units is used to adjust this absorption maxima. However, this positive effect on the solar absorption is compensated by a higher molecular weight. This implies a lower energy density. This positive effect on the solar absorption has another downside. Namely that the energy storage time is lowered when the absorption is redshifted. A possible solution to overcome this anti-correlation between the energy density and the redshifting is to couple one chromophore unit to several photo switches. In this case, it is advantageous to form so called dimers or trimers. The NBD share a common donor and/or acceptor.