Efficient organic solar cells based on phthalocyanines

The primary goal of this thesis is to develop efficient organic solar cells by utilizing metallophthalocyanines (MPc) as donor materials. The role of centered metals in MPcs is discussed, and it is shown that a suitable choice of centered metals and device engineering lead to efficient MPc based solar cells. The effect of molecular packing of organic semiconductors on interfacial recombination at a donor/acceptor interface is also discussed.;Organic solar cells based on planar metallophthalocyanines (MPc, M = Cu, Zn, Pd, Pc) / 3,4,9,10-perylene tetracarboxylic bisbenzimidazole (PTCBI) are investigated. PdPc/PTCBI solar cells have a peak external quantum efficiency of 30.9 %, which is almost two times larger than solar cells based on CuPc/PTCBI and ZnPc/PTCBI. External quantum efficiency measurement and optical modeling indicate that PdPc has longer exciton diffusion length than CuPc and ZnPc, leading to an enhanced efficiency.;Device performance of organic solar cells consisting of ZnPc and fullerene (C60) can be enhanced by insertion of a N,N'-dihexyl- perylene-3,4,9,10-bis(dicarboximide) (PTCDI-C6) intermediate layer between fullerene and bathocuproine (BCP) exciton blocking layer. Insertion of the PTCDI-C6 layer between fullerene and BCP enhances an efficiency from 1.9 to 2.5 %. The enhancement in device performances by insertion of PTCDI-C6 is attributed to reduction in device series resistances due to the promoted metal migration into BCP and optimized optical interference effects in multi-layered devices.;Electron-hole pair recombination at donor/acceptor interfaces was discussed for PdPc/PTCDI derivatives solar cells with correlation of molecular packing in PTCDI derivatives. PTCDI with hexyl chains exhibits the highest charge separation efficiency among three PTCDI derivatives.;Lastly, it is demonstrated that a power conversion efficiency of p-i-n type organic solar cells consisting of ZnPc and C60 can be enhanced by replacing ZnPc p-layer with PdPc. The optimized cell consisting of PdPc/ZnPc:C60/C60 exhibited an efficiency of 3.7 %, while the cell with the device structure of ZnPc/ZnPc:C 60/C60 showed 3.2 %. The enhancement in the efficiency is mainly attributed to increase in the short circuit current density, which is due to PdPc p-layer having longer exciton diffusion length than ZnPc.