Enhancing the photovoltaic characteristics of organic solar cells by introducing highly conductive graphene as a conductive platform for a PEDOT:PSS anode interfacial layer

Abstract

We propose a remarkably conductive polymer composite that results from highly conductive pristine graphene (PG) being doped with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). With the addition of PG to a PEDOT:PSS (B-PE) dispersion acting as a conductive platform, the sheet resistance can be lowered from 368.54/sq to 114.67/sq for the graphene-PEDOT:PSS (G-PE) over a bare glass substrate. Importantly, this only causes a minor decrease in optical transmittance of approximately 4.16% at 550nm, and generates a noticeable decrease in the surface roughness profile of similar to 11.42nm. XRD, Raman spectroscopy, and XPS analyses were used to verify that various types of chemical bonds are formed between the PG sheets and B-PE molecules. Due to these chemical interactions, a huge number of electrons are transferred from the PG sheets to the PEDOT, creating a net positive charge among the carbon atoms in the PG sheets. This results in an increase in the conductivity of the G-PE composite and, consequently, improves the power-conversion efficiency (PCE; 4.52%) of organic solar cells utilizing G-PE composite hole transport layers (HTLs). This enhancement in the PCE of G-PE HTL-based devices is compared with devices fabricated from either B-PE or PG HTLs alone, these devices achieved a PCE of only 4.18% and 3.87%, respectively.