Doped Nickel Oxide Carrier-Selective Contact for Silicon Solar Cells
Md. Anower Hossain, Tian Zhang, Yahya Zakaria, Daniel Lambert, Patrick A. Burr, Sergey N. Rashkeev, Amir Abdallah, Bram Hoex
Abstract
Transition metal oxides such as MoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , WO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5,</sub> and NiO have shown potential as hole-selective passivating contact for crystalline silicon (c-Si) solar cells. Among them, NiO is a notoriously poor hole-conducting semiconductor. Doping metal oxide with multivalent metal cations is an effective method to modify their electronic properties because dopant-induced favorable defect states play a crucial role in charge carrier transport in device applications. We use first-principles density functional theory to identify suitable metal cations that favorably affect the hole-conducting properties of NiO. We identify Al, Mg, and Zn as suitable dopants for NiO, improving ohmic contact properties with c-Si. Subsequently, Al-doped NiO (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> O) films were synthesized onto c-Si using an atomic layer deposition supercycle approach. The Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> O films showed a contact resistivity of 331 mΩ cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with c-Si, in contrast to undoped NiO where no ohmic contact could be formed. This in-depth computational study followed by the experimental synthesis of Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> O films removes a critical barrier for the future applications of NiO-based carrier-selective passivating contacts for c-Si and other types of solar cells and provides a path for the optimization of other functional materials.