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

¹ Department of Physics and Center for Nanostructures, Santa Clara University, Santa Clara CA 95053, USA
² Department of Electrical Engineering, Santa Clara University, Santa Clara CA 95053, USA

^a e-mail: rbarber@scu.edu

Received: 27 February 2014
Accepted: 19 August 2014
Published online: 6 October 2014

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 Ω-cm for pure PEDOT:PSS to 3 × 10^-2Ω-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.