Sustainable approaches to the synthesis and functionalization of phthalocyanines for optoelectronic applications

The need to work in an environmentally friendly way, has directed research towards the development of sustainable synthetic technologies and approaches, economical so as to reduce the environmental impact. Phthalocyanines are planar, aromatic macrocycles capable of hosting metal ions in their central cavity. They represent one of the main chromophore systems discovered in the 20th century and over the years have proved to be a class of very versatile compounds, in particular the electronic properties of phthalocyanines have allowed to extend their application in the field of optoelectronics and organic solar cells. Photovoltaics is a relevant technology because it allows for clean energy to be harnessed, and using a device whose construction is economical and based on components obtained through green methods makes the process more advantageous. In particular, perovskite cells use spiro-OMeTAD as hole transport material (HTM) and have achieved the highest efficiencies (25.5%). However, to synthesize this HTM many steps and careful purification procedures are required, which negatively affect the final cost of the device. The spiro can be replaced efficiently by an organic molecule such as a properly functionalized phthalocyanine with suitable electronic properties. In this contribution we will discuss green synthetic approaches for the sustainable syntheses of variously substituted metallophthalocyanines, along with some preliminary device results.