Bandgap engineered, quantum-confined ultrathin Te layer for highly effective back surface field in Si/organic hybrid solar cells

Abstract

The suppression of back surface carrier recombination is primary importance for efficient Si-based solar cells. It is usually achieved with back surface field (BSF) by introducing a highly doped layer on the rear surface, which require a high temperature doping processes and involves toxic gasses. Here, we report that a high power conversion efficiency of 13.1% with device area of 1cm2 has been achieved for planar Si-PEDOT:PSS hybrid solar cells by depositing a ultrathin tellurium (Te) layer between silicon and rear contact, without any high temperature process or further treatment. Current-voltage, electrochemical impedance spectroscopy, quasi-steady-state-photoconductance measurements are used to investigate the effect of Te BSF layer on the device performance. The insertion of Te BSF layer have successfully reduced charge carrier recombination at rear interface. In addition, it could reduce the contact resistance thanks to the favorable band alignment originated from quantum confinement effect, resulting in improved current density and fill factor. This is the very first demonstration that a quantum-confined material can be used as an effective passivating back surface field layer in Si-organic hybrid solar cells.