Modulation of the TCO/MoO x Front Contact Enables >21% High-Efficiency Dopant-Free Silicon Solar Cells

Highly efficient dopant-free silicon solar cell requires effective electron- and hole-selective contacts. We have recently reported a remarkable efficiency of 21.3% for dopant-free silicon solar cells with a low work function and transparent and conductive MgF x O y electron extraction. The transparent conductive oxide (TCO) films and molybdenum oxide (MoO x ) front hole contact also play significant roles in the high efficiency of dopant-free solar cells. In this study, zinc-doped indium oxide (IZO), tin-doped indium oxide (ITO), and titanium-doped indium oxide (ITiO) have been deposited via magnetron sputtering at room temperature. The work function and optoelectrical properties of TCO films and energy band bending together with the MoO x layer are investigated. The impact of this band bending on the photoelectrical performances of devices is analyzed in detail as a function of the MoO x /TCO work function mismatch. The optimized IZO film presents the highest work function (5.21 eV) and conductivity (2140 S/cm), resulting in reduced barrier height at the MoO x /TCO interface and enhanced hole-selective transport. The light-soaking treatment is introduced to repair the sputtered damage during the IZO deposition. Finally, an impressive cell efficiency of 21.0%, together with V oc, FF, and J sc of 712.4 mV, 76.4%, and 38.6 mA/cm 2, respectively, shows great potential and provides an effective solution to obtain highly efficient dopant-free silicon solar cells.