Effective Passivation of Black Silicon Surfaces via Plasma-Enhanced Chemical Vapor Deposition Grown Conformal Hydrogenated Amorphous Silicon Layer
E. Özkol (TU Delft - Photovoltaic Materials and Devices)
Paul Procel Moya (TU Delft - Photovoltaic Materials and Devices)
Yifeng Zhao (TU Delft - Photovoltaic Materials and Devices)
Luana Mazzarella (TU Delft - Photovoltaic Materials and Devices)
Rostislav Medlin (University of West Bohemia)
Pavol Šutta (University of West Bohemia)
Olindo Isabella (TU Delft - Photovoltaic Materials and Devices)
M Zeman (TU Delft - Electrical Sustainable Energy)
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Abstract
Solar cells based on black silicon (b-Si) are proven to be promising in photovoltaics (PVs) by exceeding 22% efficiency. To reach high efficiencies with b-Si surfaces, the most crucial step is the effective surface passivation. Up to now, the highest effective minority carrier lifetimes are achieved with atomic layer-deposited Al2O3 or thermal SiO2. Plasma-enhanced chemical vapor deposition (PECVD)-grown hydrogenated amorphous silicon (a-Si:H) passivation of b-Si is seldom reported due to conformality problems. In this current study, b-Si surfaces superposed on standard pyramidal textures, also known as modulated surface textures (MSTs), are successfully passivated by PECVD-grown conformal layers of a-Si:H. It is shown that under proper plasma-processing conditions, the effective minority carrier lifetimes of samples endowed with front MST and rear standard pyramidal textures can reach up to 2.3 ms. A route to the conformal growth is described and developed by transmission electron microscopic (TEM) images. Passivated MST samples exhibit less than 4% reflection in a wide spectral range from 430 to 1020 nm.
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