Effects of PBr3 Addition to Polysilane Thin Films on Structures and Photovoltaic Properties

摘要

Organic thin film solar cells are potential next generation solar cells. Many p-type semiconductors have been used in organic solar cells, but there have been far fewer reports involving n-type organic semiconductors. Developing new n-type organic semiconductors is therefore desirable. Polysilane thin films were spin-coated from solutions containing phosphorus (P), and the effects of P addition on film microstructures and electronic properties as n-type semiconductors were investigated. Microstructures of poly-methyl-phenyl-silane (PMPS), dimethyl-polysilane (DMPS) and deca-phenyl-penta-silane (DPPS) thin films were investigated by X-ray diffraction and transmission electron microscopy. PMPS thin films doped with P (PMPS(P)) were amorphous upon annealing at 300°C, while DMPS(P) and DPPS(P) thin films exhibited crystalline structures. PMPS(P) and DMPS(P) thin films exhibited decreased electrical resistances upon P doping. The energy gaps of PMPS(P), DMPS(P) and DPPS(P) were 3.5, 3.9 and 3.8 eV, respectively. Decreased photoluminescence intensities of PMPS, DMPS and DPPS were observed upon P doping. The desorption of phenyl and methyl groups from PMPS(P) thin films was observed from Raman scattering measurements. Solar cells containing polysilane(P)/poly[3-hexylthiophene] heterojunction structures were fabricated and exhibited photovoltaic behavior.