ROTROT (ROll to Roll production of Organic Tandem cells) project addresses "Flexible, Organic and Large Area Electronic and photonics". OLAE potentially offers a giant step for consumer electronics and will continue to address mass market applications. In this OLAE field, Organic Photovoltaic (OPV) has to compete with Si and Thin Film PV. OPV has followed this tremendous growth and makes important additions to the motivation: low cost and easy manufacturing on flexible substrates by printing technologies. The problem of harvesting energy from light naturally presents a large area challenge and no manufacturing technique is faster than printing and coating under ambient conditions in terms of manufactured surface per unit time. This is in reality what gives OPV the competitive advantage over all other PV technologies.Power conversion efficiency of OPV cells has relatively been growing +0.5% per year from 1990. This enhancement is mainly due to new performing material discovery. If we want to reach relative growth up to 1 to 2% per year, we still have to work on new high absorbing polymers but also put great effort on device architecture design like the tandem structure. Novel disruptive concepts are required involving cheaper production of multilayered printed cells based on innovative engineered architectures (R2R printed tandem cell), new high performance materials (low band gap Eg ~1.5 eV, electrodes, high performance interface, barrier adhesive). Such innovative solutions are necessary for the technology to reach further than today's niche markets and to overcome the limitations by improving at least two times the currently achieved efficiency (12%), improving the lifetime by more than factor 4 from today's known OPV cell and reducing the cost (down to 0.7€/Wp). ROTROT proposes to fulfill these goals and comprise a complete solution process using significant advances in R2R techniques ending up with an environmentally friendly and safe deposition process