title: Nanohole Structuring for Improved Performance of Hydrogenated Amorphous Silicon Photovoltaics.
abstract: While low hole mobilities limit the current collection and efficiency of hydrogenated amorphous silicon (a-Si:H) photovoltaic devices, attempts to improve mobility of the material directly have stagnated. Herein, we explore a method of utilizing nanostructuring of a-Si:H devices to allow for improved hole collection in thick absorber layers. This is achieved by etching an array of 150 nm diameter holes into intrinsic a-Si:H and then coating the structured material with p-type a-Si:H and a conformal zinc oxide transparent conducting layer. The inclusion of these nanoholes yields relative power conversion efficiency (PCE) increases of ∼45%, from 7.2 to 10.4% PCE for small area devices. Comparisons of optical properties, time-of-flight mobility measurements, and internal quantum efficiency spectra indicate this efficiency is indeed likely occurring from an improved collection pathway provided by the nanostructuring of the devices. Finally, we estimate that through modest optimizations of the design and fabrication, PCEs of beyond 13% should be obtainable for similar devices.
authors.affiliation: Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Johlin
authors.affiliation: Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Al-Obeidi
authors.affiliation: École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Gizem
authors.initials: G
authors.lastname: Nogay
authors.affiliation: École Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Stuckelberger
authors.affiliation: Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Tonio
authors.initials: T
authors.lastname: Buonassisi
authors.affiliation: Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Grossman
keywords: amorphous silicon; charge collection; efficiency; nanohole; nanostructuring; photovoltaics; thin-film solar cells