G8 Initiative: Inkjet printing high-performance organic small-molecule optoelectronic devices

87% of global primary energy production in 2010 was derived from unsustainable fossil fuels [1] and as energy consumption grows (28% in last 10 years) [1], we urgently need to move towards renewable, clean energy sources [2]. Only ¡«36 kWh/day/person could realistically be generated by non-solar renewable production [2], falling short of the global target of 80 kWh/day/person [2]. Therefore, without relying on nuclear, solar energy must fill the gap. To meet demand, we require as many on- and off-grid photovoltaic (PV) technologies as possible [3, 4] and development of sustainable, low-energy and material-light technologies should be prioritized. In this context, solution-processed organic photovoltaics (OPVs) are highly attractive. OPVs are inherently sustainable for a number of reasons. Firstly, similar to other thin-film photovoltaic technologies, such as copper indium (di)selenide (CIS) or cadmium telluride (CdTe), OPVs require only small amounts of active material (¡«100 nm active layer thickness compared with 200-300 ¦Ìm for silicon solar cells) and are therefore far more material-efficient than standard ¡®bulk¡¯ PV technolgies. In addition, the ability to solution process OPVs allows the use of printing or spraycoating which do not waste material and work at low temperatures thus further reducing energy consumption. The low-temperature processing also enables the use of heat-sensitive substrates such as plastics, allowing high throughput roll-to-roll (R2R) manufacturing. All of these factors mean that OPVs can be produced with significantly lower initial energy input compared with all other photovoltaic technologies. Life-cycle analysis shows that the energy required to fabricate 1 m of solar cell is almost 14 times smaller for the OPV compared with single-crystalline silicon and almost 10 times smaller than the energy requirement for CIS thin film PVs.