Improving Junction Quality via Modifying the Si Surface to Enhance the Performance of PEDOT:PSS/Si Hybrid Solar Cells

PEDOT:PSS/Si hybrid solar cells have attracted wide attention due to the fabrication of an inversion layer near the Si surface by a solution method to realize high efficiency. However, Si dangling bonds on the Si surface produce surface states and lattice mismatches to deteriorate the performance of the solar cells. In this work, the aromatic rubrene is used to modify the Si dangling bonds to passivate the Si surface for improving the junction quality of PEDOT:PSS/Si. It is found that the interaction of rubrene with Si dangling bonds reduces the binding energies of Si 2p1/2 and Si 2p3/2 by 0.2 and 0.1 eV, respectively. These large shifts of Si 2p core levels are the signals that form a stronger inversion layer for a higher quality junction. In addition, rubrene increases the work function of the PEDOT:PSS film by 0.09 eV to increase the band bending of the Si interface to promote carrier separation. Finally, the power conversion efficiency (PCE) of PEDOT:PSS/Si hybrid solar cells with rubrene is 12.59%, which is 23.92% higher than that without rubrene.