Graphene Oxide as an Effective Interface Passivation Layer for Enhanced Performance of Hybrid Silicon Solar Cells

Abstract

Hybrid solar cells (HSCs) using poly (3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a hole selective layer on n-silicon (n-Si) is considered a promising alternative to conventional dopant-diffused Si solar cells because of their simple, low-cost processing yet reasonable efficiency. The interface between PEDOT:PSS and Si governing the recombination of charge carriers plays a critical role in the performance of HSCs. Here, the interface properties of the PEDOT:PSS/n-Si are engineered by introducing a graphene oxide (GO) interlayer. A significantly enhanced (∼7-fold) minority carrier lifetime (MCLT) of the Si has been achieved with an ultrathin (thickness: ∼5 nm) GO interlayer (GO/n-Si/GO), indicating its excellent passivation properties. The properties of the GO/n-Si interface have been analyzed using C−V characteristics of the metal oxide semiconductor (MOS) structure (metal/ GO/n-Si), confirming the presence of negative fixed charges at the interface due to the GO interlayer. The MCLT is further enhanced to >45 μs (∼25 times as compared to unpassivated microtextured n-Si) after applying the bilayer of PEDOT:PSS (PEDOT:PSS/GO/n-Si/GO/PEDOT:PSS) on n-Si surfaces. The structural and interface properties of the PEDOT:PSS and GO interlayer are investigated by X-ray photoelectron spectroscopy (XPS), XPS valence band spectra, and Raman spectroscopy analyses. Moreover, significant enhancement in the performance of the PEDOT:PSS/n-Si HSCs (by absolute >3.1%) is observed with the GO interlayer as compared to that of the control cell without GO. Impedance spectroscopy (IS) and dark characteristics results confirmed the formation of a strong inversion layer at the junction, having a high built-in potential after applying the GO interlayer. The application has also been complemented by a detailed surface and interface morphology (field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM)), surface reflectance properties, and quantum efficiency of the HSCs. This study will strengthen the application of thin GO as an effective interface layer for efficient hybrid solar cells.