A Two-Step Absorber Deposition Approach To Overcome Shunt Losses in Thin-Film Solar Cells: Using Tin Sulfide as a Proof-of-Concept Material System

TitleA Two-Step Absorber Deposition Approach To Overcome Shunt Losses in Thin-Film Solar Cells: Using Tin Sulfide as a Proof-of-Concept Material System
Publication TypeJournal Article
Year of Publication2016
AuthorsSteinmann, V, Chakraborty, R, Rekemeyer, PH, Hartman, K, Brandt, RE, Polizzotti, A, Yang, C, Moriarty, T, Gradecak, S, Gordon, RG, Buonassisi, T
JournalAcs Applied Materials & Interfaces
Volume8
Issue34
Pagination22664 - 22670
Date Published2016/08/31/
ISBN Number1944-8244
KeywordsAtomic Layer Deposition, defect-tolerant semiconductors, device shunting, energy conversion, novel absorber materials, performance reliability, photovoltaic-device, Photovoltaics, thin-films, tin sulfide
Abstract

As novel absorber materials are developed and screened for their photovoltaic (PV) properties, the challenge remains to reproducibly test promising candidates for high-performing PV devices. Many early-stage devices are prone to device shunting due to pinholes in the absorber layer, producing "false-negative" results. Here, we demonstrate a device engineering solution toward a robust device architecture, using a two-step absorber deposition approach. We use tin sulfide (SnS) as a test absorber material. The SnS bulk is processed at high temperature (400 degrees C) to stimulate grain growth, followed by a much thinner, low-temperature (200 degrees C) absorber deposition. At a lower process temperature, the thin absorber overlayer contains significantly smaller, densely packed grains, which are likely to provide a continuous coating and fill pinholes in the underlying absorber bulk. We compare this two-step approach to the more standard approach of using a semi-insulating buffer layer directly on top of the annealed absorber bulk, and we demonstrate a more than 3.5X superior shunt resistance R-sh with smaller standard error sigma(Rsh). Electron-beam-induced current (EBIC) measurements indicate a lower density of pinholes in the SnS absorber bulk when using the two-step absorber deposition approach. We correlate those findings to improvements in the device performance and device performance reproducibility.

Short TitleACS Appl. Mater. Interfaces