Phthalocyanines and Subphthalocyanines: Perfect Partners for Fullerenes and Carbon Nanotubes in Molecular Photovoltaics

The huge interest towards fullerenes and carbon nanotubes in molecular materials and materials science is closely related to the intriguing properties of these carbon nanostructures such as their excellent electrical conductivity and remarkable chemical stability, among others. In this connection, organic photovoltaics (OPVs) is one of the research fields where these carbon allotropes have been extensively employed, mainly as electron-accepting materials. Among the electron-donating counterparts, phthalocyanines (Pcs) and subphthalocyanines (SubPcs) are some organic compounds largely used for this pourpose mainly due to their intense light-harvesting ability in the red and near infrared region of the solar spectrum, and rich and tuneable redox chemistry. In this review, we summarize some of the most recent and relevant achievements in the preparation of fullerene-and carbon nanotube-based OPVs containing Pcs and/or SubPcs, paying a special attention to the effect that i) the structural and electronic modifications of the Pc and SubPc derivatives, ii) the different type of OPV architecture, and iii) the preparation method, have on the performance of the OPV devices. A section of this review has been also devoted to the used of SubPcs as electron-accepting materials in fullerene-free PV cells highlighting the great potential of these class of materials for the preparation of efficient organic solar cells.