2014 Microscopy and Microanalysis

MandMEffects of Focused-Ion-Beam Processing on Local Electrical Measurements of Inorganic Solar Cells“, H. P. Yoon, P. M. Haney, J. Schumacher, K. Siebein, Y. Yoon, and N. B. Zhitenev, Microscopy and Microanalysis 20 (S3), 544-545, 2014.

1.Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
2. Maryland Nanocenter, University of Maryland, College Park, MD 20742, USA

ABSTRACT. Quantitative determination of electronic properties at high spatial resolution is crucial for the development of high-efficiency solar cells. Electron beam induced current (EBIC) is a powerful technique in which electron-hole pairs are created in proximity to an exposed surface, and the carrier collection efficiency is measured as a function of excitation position. Cross-sections of device are often created by focused ion beams (FIB) due to the flexibility of the patterning and milling processes. However, the irradiating Ga ions of the FIB fabrication may introduce unintended artifacts, affecting local electronic properties. In this study, we investigate the impact of the FIB process observed in EBIC measurements and two-dimensional finite element simulations.


2014 Progress in Photovoltaics

pip_epi_EBIC“Comparison of thin epitaxial film silicon photovoltaics fabricated on monocrystalline and polycrystalline seed layers on glass”, C. W. Teplin, S. Grover, A. Chitu, A. Limanov, M. Chalal, J. Im, D. Amkreutz, S. Gall, H. P. Yoon, V. Lasalvia, H. M. Branz, P. Stradins, K. M. Jones, A. G. Norman, D. L. Young, B. Lee, Progress in Photovoltaics, in press (DOI: 10.1002/pip.2505), 2014.

1. National Renewable Energy Laboratory, Golden, CO, USA
2. Columbia University, New York, NY, USA
3. Helmholtz Zentrum Berlin für Materialien und Energie, Berlin, Germany
4. Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA

ABSTRACT:  We fabricate thin epitaxial crystal silicon solar cells on display glass and fused silica substrates overcoated with a silicon seed layer. To confirm the quality of hot-wire chemical vapor deposition epitaxy, we grow a 2-μm-thick absorber on a (100) monocrystalline Si layer transfer seed on display glass and achieve 6.5% efficiency with an open circuit voltage (V_OC) of 586mV without light-trapping features. This device enables the evaluation of seed layers on display glass. Using polycrystalline seeds formed from amorphous silicon by laser-induced mixed phase solidification (MPS) and electron beam crystallization, we demonstrate 2.9%, 476mV (MPS) and 4.1%, 551mV (electron beam crystallization) solar cells. Grain boundaries likely limit the solar cell grown on the MPS seed layer, and we establish an upper bound for the grain boundary recombination velocity (S_GB) of 1.6×104 cm/s.