Resistance and lifetime measurements of polymer solar cells using glycerol doped poly[3,4-ethylenedioxythiophene]: poly[styrenesulfonate] hole injection layers

TL;DR

This study investigates how glycerol doping affects the resistivity, efficiency, and lifetime of polymer solar cells with PEDOT:PSS electrodes, revealing that glycerol reduces resistance but may shorten device lifespan.

Contribution

It provides new insights into the effects of glycerol doping on PEDOT:PSS layers, linking resistivity changes to device performance and stability in polymer solar cells.

Findings

Glycerol doping decreases PEDOT:PSS resistivity exponentially.

Lower resistivity correlates with higher device efficiency.

Increased glycerol content tends to reduce device lifetime.

Abstract

We have performed resistivity measurements of poly[3,4-ethylenedioxythiophene]: poly[styrenesulfonate] (PEDOT:PSS) films with varying concentrations of glycerol. Resistivity is seen to decrease exponentially from roughly 3 ohm-cm for pure PEDOT:PSS to 3x10-2 ohm-cm for 35 mg/cm3 glycerol in PEDOT:PSS. Beyond this concentration adding glycerol does not significantly change resistivity. Bulk heterojunction polymer solar cells using these variously doped PEDOT:PSS layers as electrodes were studied to characterize the effects on efficiency and lifetime. Although our data display significant scatter, lowering the resistance of the PEDOT:PSS layers results in lower device resistance and higher efficiency as expected. We also note that the lifetime of the devices tends to be reduced as the glycerol content of PEDOT:PSS is increased. Many devices show an initial increase in efficiency followed by a roughly exponential decay. This effect is explained based on concomitant changes in the zero bias conductance of the samples under dark conditions.