Poly(3,4 ethylenedioxythiophene): Poly(styrenesulfonate)llron(III) Porphyrin Supported on S and N Co-Doped Graphene Quantum Dots as a Hole Transport Layer in Polymer Solar Cells

We report the use of composite layers of solution-processable poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and various graphene quantum dots (GQDs) as hole transport layers (HTLs) in high-performance polymer solar cells (PSCs). Three types of GQDs N-doped GQDs, S and N co-doped GQDs (S, N: GQDs), and Fe(III)tetra(4-sulfonatophenyl) porphyrin (FeTSPP) supported on S, N: GQDs and their composites with PEDOT:PSS were tested in PSCs. The PEDOT:PSS/FeTSPP@S, N: GQD composite HTL showed increased charge carrier transport due to enhanced conductivity resulting from the benzoid-quinoid transition and the well-matched work function between the FeTSPP@S, N: GQDs and PEDOT:PSS. Indeed, the PEDOT:PSS/FeTSPP@S, N: GQD composite HTL yielded an outstandingly improved power conversion efficiency (PCE) of 4.68% in PSCs, with a much more reproducible performance and longer lifetime than a reference PSC with a PEDOT:PSS HTL (PCE = 3.17%).