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Local Measurements of Photocurrent and Band Gap in CdTe Solar Cells
Y. Yoon, J. Chae, A. Katzenmeyer, H. Yoon, J. Schumacher, S. An, A. Centrone, N. Zhitenev
Subtopic: CdTe, CIS and Related Ternary and Quaternary Thin Film Solar Cells and Modules
Event: 31st European Photovoltaic Solar Energy Conference and Exhibition
Session: 3DV.1.34
1243 - 1245
ISBN: 3-936338-39-6
Paper DOI: 10.4229/EUPVSEC20152015-3DV.1.34
0,00 EUR
Document(s): paper


Polycrystalline thin film technology has shown great promise for low cost, high efficiency photovoltaics. To further increase the power efficiency, a better understanding of microstructural properties of the devices is required. In this work, we investigate the inhomogeneous electrical and optical properties using local excitation techniques that generate excess carriers by a near-field light illumination or by a focused electron beam irradiation. The spatially-resolved photocurrent images of n-CdS / p-CdTe devices obtained by both techniques show high carrier collection efficiencies at grain boundaries. A novel and complementary technique, photothermal induced resonance (PTIR), is also used to obtain absorption spectra and maps in the near-field over a broad range of wavelengths. In PTIR a wavelength tunable pulsed laser is used in combination with an atomic force microscope tip to detect the local thermal expansion induced by light absorption. Sub-micrometer thick lamella samples of CdTe solar cells are measured, and the variation of local band-gap is analyzed. We discuss the resolution and the sensitivity of the techniques in the range of photon energies close to the band gap. Keywords: photothermal induced resonance (PTIR), CdTe solar cells, band-gap, scanning photocurrent microscopy (SPCM), near-field scanning optical microscopy (NSOM)