Simulated Study and Surface Passivation of Lithium Fluoride-Based Electron Contact for High-Efficiency Silicon Heterojunction Solar Cells

Abstract

Numerical simulation and experimental techniques were used to investigate lithium fluoride (LiF x ) films as an electron extraction layer for the application of silicon heterojunction (SHJ) solar cells, with a focus on the paths toward excellent surface passivation and superior efficiency. The presence of a 7 nm thick hydrogenated intrinsic amorphous silicon (a-Si:H(i)) passivation layer along with thermally evaporated 4 nm thick LiF x resulted in outstanding passivation properties and suppresses the recombination of carriers. As a result, minority carrier lifetime ( τ eff ) as well as implied open-circuit voltage (iV oc ) reached up 933 μ s and iV oc of 734 mV, accordingly at 120 °C annealing temperature. A detailed simulated study was performed for the complete LiF x based SHJ solar cells to achieve superior efficiency. Optimized performance of SHJ solar cells using a LiF x layer thickness of 4 nm with energy bandgap (E g ) of 10.9 eV and the work function of 3.9 eV was shown as: V oc = 745.7 mV, J sc = 38.21 mA cm −2 , FF = 82.17%, and η = 23.41%. Generally, our work offers an improved understanding of the passivation layer, electron extraction layer, and their combined effects on SHJ solar cells via simulation.