Subscriber access provided by University of Victoria Libraries
Surfaces, Interfaces, and Applications
Correlation between In Situ Diagnostics of the Hydrogen Plasma and the Interface Passivation Quality of Hydrogen Plasma Post-Treated a-Si: H in Silicon Heterojunction Solar Cells Anishkumar Soman, Ugochukwu Nsofor, Ujjwal K Das, Tingyi Gu, and Steven S. Hegedus ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b01686 • Publication Date (Web): 05 Apr 2019 Downloaded from http://pubs.acs.org on April 7, 2019
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Materials & Interfaces
Correlation between In Situ Diagnostics of the Hydrogen Plasma and the Interface Passivation Quality of Hydrogen Plasma Post-Treated a-Si: H in Silicon Heterojunction Solar Cells Anishkumar Soman1*, Ugochukwu Nsofor1, 2, Ujjwal Das2, Tingyi Gu1, Steven Hegedus1, 2 1
Department of Electrical and Computer Engineering, University of Delaware, Newark, DE, USA 19716 2
Institute of Energy Conversion, University of Delaware, Newark, DE, USA 19716 *Corresponding author:
[email protected] Abstract: Passivation of the interface defect states is crucial to mitigate the recombination losses in Silicon solar cells. In this work we have investigated the role of hydrogen plasma treatment (HPT) to passivate the interfacial defects between crystalline (c-Si) and hydrogenated amorphous silicon (a-Si:H) in Heterojunction (SHJ) solar cells. For the first time we have found a correlation between the dynamic properties of hydrogen plasma and passivation quality of the films by using in-situ optical emission spectroscopy and quasi-steady state photoconductance measurement. The optimum condition for saturation of the dangling bonds by HPT has been studied in detail by tuning the excited Hydrogen (H) species and ion bombardment energies by controlling physical parameters like Plasma current and chamber pressure. We have investigated the role of annealing after HPT to redistribute the H in the post treated a-Si:H film and have obtained iVoc of 755 mV, minority carrier lifetime (eff) of 4.6 ms and SRV of 1.5 cm/s on test structures having only 8 nm of intrinsic a-Si:H layer on textured silicon wafers. The H bond configuration at the interface of a-Si:H and c-Si has been investigated by Fourier Transform Infrared spectroscopy, which demonstrates improved monohydride bonding in the films after HPT derived from the analysis of microstructure parameter and H concentration values. Raman Spectroscopy shows the absence of nanocrystalline fraction after HPT and verifies reduces co-ordination defects due to annealing after HPT. The proof of concept has been validated by fabrication SHJ solar cells having V oc of 729 mV and efficiency of 18.7% after HPT, with the best cell efficiency reaching 20.2% after doped layer optimization. The decrease in reverse saturation current and ideality factor after HPT verifies that the improvement in performance is from reduced recombination losses at the interface due to passivation of defects in midgap states. Keywords: hydrogen plasma, heterojunction solar cell, surface passivation, a-Si:H/c-Si interface, DC-PECVD 1. Introduction: Silicon Heterojunction (SHJ) solar cells are a commercially viable photovoltaics technology due to their demonstrated high efficiency, lower temperature coefficient, lower thermal budget (
