Highly efficient SiNWs/PEDOT:PSS Hybrid Solar Cells Achieved by Conformal Coating

Abstract

In recent years, organic/inorganic hybrid solar cells have attracted much attention owing to the synergetic advantages of the high carrier mobility and efficiency from the inorganic semiconductor and the simple process and low cost from the organic semiconductor. In this work, we prepared an array of silicon nanowires (SiNWs) with a controlled diameter and pitch interval using a metal-assisted chemical (MAC) etching and fabricated an organic/inorganic SiNWs/PEDOT:PSS solar cell. Due to large difference of the electron affinity of Si (4.0 eV) and PEDOT:PSS (5.0 eV), the heterointerface between n-type Si and PEDOT:PSS behaves like a Schottky diode. The MAC etching was carried out in aqueous HF/H2O2 solution using Au mesh patterns, which were prepared by the deposition of 20-nm-thick Au layer on self-assembled ITO nanodots, followed by subsequent removal of ITO nanodots by sonication. The reflectance of SiNWs surface was dramatically reduced below 5%, compared ~ 35% of planar Si wafer in the visible-to-NIR regions from 300 to 1100 nm, which is in good agreement with the simulation results using COMSOL Multiphysics. To fabricate an organic/inorganic hybrid solar cell, we spin-coated PEDOT:PSS on top of Si nanowires. We prepared two types of hybrid solar cells with different surface treatments on Si nanowires, one with BOE and the other with HNO3 and we observed HNO3 removed the etching damage, which improved the wettability of PEDOT : PSS. The HNO3-treated solar cell represented the power conversion efficiency (PCE) of 15%, which is significantly higher than 13.1% of that with BOE treatment and even comparable to conventional Si solar cells. The enhancement of PCE was ascribed to the better conformal coating of PEDOT:PSS on HNO3-treated Si surface because of the hydrophilic property. Our approaches propose a new way to fabricate highly efficient organic/inorganic hybrid solar cells.