The optical transmittance, electrical conductivity and morphology of PEDOT:PSS treated with ammonium hydroxide
(
NH4OH) have been investigated. Transmittance spectra of spun PEDOT:PSS layers were enhanced slightly as a result
NH4OH
treatment while surface of the films has exhibited variation in the roughness and an increase in the electrical
conductivity. Improvement in the physical properties of PEDOT:PSS is shown to be the key factor in enhancing the power
conversion effeciency (PCE) with values as high as 4% associated with high fill factor (FF) of 57%, open circuit voltage
(
VOC) of 0.64 V and larger short circuit current density (
JSC) of 11 mA cm?2. Stabiltiy test of the devices has been carried
out over a period of 2 months, when a device incorporating PEDOT:PSS with pH ~ 4 as the hole transport layer has shown
an improved stability with a degredation in PCE in about 43% whereas JSC
has decreased in about 20% compared to a device
incorporating pristine PEDOT:PSS with PCE decreased in about 66% and JSC
in about 50% over the stated period of test.
These effects have been ascribed to the increased acidity of the hole transport layer.