Prolonged Annealing Improves Hole Transport of Silicon Heterojunction Solar Cells

The Schottky barrier is a fundamental issue when an n‐type transparent conductive oxide (TCO) is contacted with p‐type hydrogenated amorphous silicon (p‐a‐Si:H) in silicon heterojunction (SHJ) solar cells. Herein, it is found that the hydrogen (H) atoms in p‐a‐Si:H diffuse into tungsten‐doped indium oxide (IWO) during annealing, which improves the electric properties of both the IWO films and the p‐a‐Si:H/IWO interface. H diffusion reduces the surface work function of p‐a‐Si:H, and thus reduces the Schottky barrier between the p‐a‐Si:H and the IWO. Consequently, it improves the hole transport of SHJ solar cells; i.e., both the fill factor (FF) and power conversion efficiency (PCE) substantially increase. These findings provide a new strategy to optimize the FF of SHJ solar cells.