High-efficiency inverted polymer solar cells via dual effects of introducing the high boiling point solvent and the high conductive PEDOT:PSS layer

Polymer solar cells (PSCs) are of great interest in the past decade owing to their potentially low-cost in the manufacturing by the solution-based roll to roll method. In this paper, a novel inverted device structure was introduced by inserting a high conductive PEDOT:PSS (hcPEDOT:PSS) layer between the Au nanoparticles (NPs)-embedded hole transport layer(PEDOT:PSS) and the top electrode layer. Power conversion efficiency (PCE) initially reached up to 4.51%, illustrating �10% higher compared with the device similarly enhanced by Au NPs plasmonics where only one PEDOT:PSS layer with the embedded Au NPs was used in single bulk heterojunction inverted PSCs based on the poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM). The PCE was further improved from 4.51% to 5.01% by adding the high-boiling point solvent of 1,8-diiodooctane (DD) into the active layer, presenting �20% enhancement in PCE through dual effects of introducing the high boiling point solvent and the high conductive PEDOT:PSS layer. Morphologies of the active layers were characterised by SEM and AFM separately in the paper.