title: Si Radial p-i-n Junction Photovoltaic Arrays with Built-In Light Concentrators.
abstract: High-performance photovoltaic (PV) devices require strong light absorption, low reflection and efficient photogenerated carrier collection for high quantum efficiency. Previous optical studies of vertical wires arrays have revealed that extremely efficient light absorption in the visible wavelengths is achievable. Photovoltaic studies have further advanced the wire approach by employing radial p-n junction architectures to achieve more efficient carrier collection. While radial p-n junction formation and optimized light absorption have independently been considered, PV efficiencies have further opportunities for enhancement by exploiting the radial p-n junction fabrication procedures to form arrays that simultaneously enhance both light absorption and carrier collection efficiency. Here we report a concept of morphology control to improve PV performance, light absorption and quantum efficiency of silicon radial p-i-n junction arrays. Surface energy minimization during vapor phase epitaxy is exploited to form match-head structures at the tips of the wires. The match-head structure acts as a built-in light concentrator and enhances optical absorptance and external quantum efficiencies by 30 to 40%, and PV efficiency under AM 1.5G illumination by 20% compared to cylindrical structures without match-heads. The design rules for these improvements with match-head arrays are systematically studied. This approach of process-enhanced control of three-dimensional Si morphologies provides a fab-compatible way to enhance the PV performance of Si radial p-n junction wire arrays.
authors.affiliation: †Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Jinkyoung
authors.initials: J
authors.lastname: Yoo
authors.affiliation: †Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Binh-Minh
authors.initials: BM
authors.lastname: Nguyen
authors.affiliation: ‡Materials Physics and Applications-11, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: Ian H
authors.initials: IH
authors.lastname: Campbell
authors.affiliation: §Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, California 92093, United States.
authors.forename: Shadi A
authors.initials: SA
authors.lastname: Dayeh
authors.affiliation: ⊥Sharp Laboratories, Camas, Washington 98607, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Schuele
authors.affiliation: ⊥Sharp Laboratories, Camas, Washington 98607, United States.
authors.forename: David
authors.initials: D
authors.lastname: Evans
authors.affiliation: †Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
authors.forename: S Tom
authors.initials: ST
authors.lastname: Picraux
keywords: finite difference time domain calculation; photovoltaic; quantum efficiency; radial p-n junction; silicon nanowire