Molecular thin films for optoelectronic applications

Organic molecular beam deposition (OMBD) is used for co-evaporation of copper phthalocyanine (CuPc) and C-60 to form mixed films. Although pure single layers are crystalline, mixing leads to amorphous films in most cases, although phase segregation occurs for high concentrations of C-60 center dot An underlying CuPc single layer suppresses the segregation and leads to a homogeneous CuPc/C-60 mixed film for all layer compositions. These effects are exploited in photovoltaic (PV) devices, where new architectures to improve device performance are investigated. Mixing the CuPc and C-60 improves device performance, with the maximum efficiency (eta(p) = 1.17%) reached for devices containing 75% CuPc in the mixed layer, surrounded by pure layers at the electrode interfaces.