Bis(5,7-dimethyl-8-hydroxyquinolinato)platinum(II) complex for efficient organic heterojunction solar cells

Organic photovoltaic (OPV) cells using metal(II) (Pt, Pd, Cu, and Ni) chelates of 8-hydroxyquinoline (Hq) or 5,7-dimethyl-8-hydroxy-quinoline (HMe₂q) as an electron donor were fabricated by vacuum deposition. The bis(5,7-dimethyl-8-hydroxyquinolinato)platinum(II) [Pt(Me₂q) ₂]-based OPVs showed the best performance with an open voltage (V_OC) of 0.42 V, a short circuit current density (J_SC) of 14.8 mA cm^-2, and a maximum power conversion efficiency (η_P) of 2.4 %. The X-ray single-crystal structures together with the grazing incidence X-ray diffraction (GIXRD) data of thin film samples reveal that the peripheral methyl substituent(s) and platinum(II) ion are essential for the high degree of film crystallinity resulting in improved performance of the as-fabricated field-effect transistors (FETs) and OPV cells. Splinter Cell: Organic photovoltaic cells using bis(5,7-dimethyl-8-hydroxyquinolinato) platinum(II) [Pt(Me₂q)₂] showed the best performance (η_P=2.4 %) among the other [Mq₂] or [M(Me ₂q)₂] complexes prepared in this work. The crystal structures together with the GIXRD data of thin films of these metal(II) complexes revealed that both the peripheral methyl substituent(s) and Pt ^II ion play pivotal role to the performance of the FETs and OPV cells.