High-Efficiency Si/PEDOT:PSS Hybrid Heterojunction Solar Cells Using Solution-Processed Graphene Oxide as an Antireflection and Inversion-Induced Layer

Due to their high photoelectric conversion efficiency (PCE) and low-cost fabrication process, n-type silicon (n-Si)/poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid heterojunction solar cells (HHSCs) have received extensive attention. However, inferior junction quality and the lower open-circuit voltage (Voc) hinder further improvement in PCE. Here, we have prepared a graphene oxide (GO) layer between the Ag electrode and PEDOT:PSS layer in Si/PEDOT:PSS HHSCs by using a solution process. The study reveals that a strong inversion layer has been established near the Si/PEDOT:PSS interface, resulting in the Si/PEDOT:PSS junction converting into a quasi p–n junction. The inversion effect enhances the built-in potential (Vbi) and suppresses the carrier recombination at the interface of Si/PEDOT:PSS. Moreover, solution-processed GO on PEDOT:PSS is a proper antireflection layer to reduce reflection because of its well-matched refractive index. As a result, the planar-Si/PEDOT:PSS/GO HHSC displays a highest PCE of 13.76% with a satisfactory short-circuit current (Jsc) and Voc of 28.59 mA/cm2 and 648 mV, respectively, which is obviously higher than that of the devices without a GO layer. The PCE is further improved to 15.43% by using a textured Si substrate. These findings provide a method for the fabrication of high-performance and low-cost Si-based heterojunction solar cells.