Influence of the PEDOT-PSS layer on the performance of the photovoltaic devices

摘要

An analysis of any peculiarities of the I" characteristic of theglass/ITO/PEDOT:PSS/MEH-PPV:PCBM(1:4) organic photovoltaic cell, that areabsent in the same characteristic of the glass/ITO/MEH-PPV:PCBM(1:4) cell, showsthat the conducting PEDOT:PSS polymer layer contributes to the decreases of boththe cell serie resistence (RS) and global dielectric constant (cell) as photodevice mainelectrical parameters. The RS decrease with increasing of the forward voltage can beassociated with the field-assisted emission (Poole-Frenkel effect) of electrons fromthe coulombic traps in p-doped PEDOT component of the PEDOT:PSS polymerlayer. On the other hand, in light conditions, the PEDOT:PSS/MEH-PPV:PCBM(1:4)interface region generated by the interdiffusion of the two polymer layers chains,having the constanta dielectrica lower that than of each isolated polymer layers,improves an increase of the exciton diffusion efficiency by the FRET mechanismspredominantly intrachain in the active MEH-PPV polymer layer. The disposition ofthe PEDOT chains in their interface region favors also the transport of thephotocarriers generated by exciton dissociation via intrachain hopping mechanism,improving the cell transport efficiency. The presence of PEDOT:PSS as buffer layerin the structure of the organic solar cell using the conjugated polymer MEH-PPV:PCBM(1:4) as active layer, improves the conversion performance by enhancement ofits components, as hole collection, exciton diffusion, photocarrier mobility.