Influence of alcoholic polar surfactants on PEDOT:PSS for enhanced performance of organic/Si hybrid solar cell

Abstract

Conducting polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), has gained prominent interests in organic/n-Si hybrid solar cells (HSCs). Alcoholic polar solvents, 2-propanol (IPA) or methanol (MeOH) addition in PEDOT:PSS by simple solution mixing process have been investigated to arrest the critical issues related to poor affinity of aqueous (aq.) PEDOT:PSS on Si surface, a key prerequisite for efficient HSCs. Remarkably enhanced electrical conductivity of the polymer layer has been found for 100 v/v% IPA and 70 v/v% MeOH addition to the aq. PEDOT:PSS. Formation and performance of the PEDOT:PSS/n-Si junction under various concentration of the IPA and MeOH addition are investigated and compared with that of aq. PEDOT:PSS. The optimum IPA or MeOH addition led to structural modification of aq. PEDOT:PSS from coil-like benzoid to linear quinoid one and hence improved electrical properties. The polar solvents not only served as the surfactant leading to conductive PEDOT:PSS conformal coverage on the micro-textured Si surface but also offered modulation of optical, electrical, structural, morphological, and passivation properties of the polymer layer. Improved solar cell performance with maximum efficiency >11.50% could be achieved for optimum IPA added PEDOT:PSS/n-Si solar cells, which is ∼2.5 fold enhanced compared to that with aq. PEDOT:PSS. The study may lead to better understanding of PEDOT:PSS/n-Si interface and efficient hybrid photovoltaic devices employing the cost-effective polar surfactants.