Characterization of Cuprous Oxide Thin Films for Application in Solar Cells

Abstract

Cuprous oxide (Cu2O) has a high optical absorption coefficient and favourable electrical properties, which make Cu2O thin films attractive for photovoltaic applications. Using reactive radio-frequency magnetron sputtering, high quality Cu2O thin films with good carrier transport properties were prepared. This paper presents the characteristics of Cu2O thin films that were sputter deposited on quartz substrates and subjected to post-deposition rapid thermal annealing. The thickness of the thin films and the optical constants were determined by ellipsometry spectroscopy (SE). The optical transmittance increased in lower wavelength region after annealing at 900 ̊C in rapid thermal annealing (RTA). The structural and morphological properties of the Cu2O thin films were investigated by electronic scanning microscopy (SEM) and atomic force microscopy (AFM), whereas elemental analysis was performed by X-ray fluorescence spectroscopy (XRF). The carrier mobility, carrier density and film resistivity were changed after post-deposition rapid thermal annealing from respectively ~14 cm2/Vs, ~2.3 x 1015 cm-3 and ~193 Ωcm for the as-deposited Cu2O film to ~49 cm2/Vs, ~5.0 x 1014 cm-3 and ~218 Ωcm for the annealed Cu2O film. The investigation suggests that the sputter-deposited Cu2O thin films have good potential for application as absorber layers in solar cells.

Insights into Cu2O thin film absorber via pulsed laser deposition

“…The electrical properties of the samples A, B, C, and D obtained from the hall measurement are listed in Table 3. All the Cu2O films reported here are p-type with a Hall concentration in the range of 10 15 cm -3 , which is consistent with the Cu2O films prepared via other techniques [3,55,56]. In particular, it should be noticed that sample A (deposited at 750 °C and10 -2 mbar oxygen partial pressure) could demonstrate a resistivity as low as 16 Ω•cm and high mobility of 30 cm 2 /(V•s) at room temperature.…”

“…As it is non-toxic, abundant, and low cost, it greatly fulfills the economic and environmental conditions for large-scale applications [2]. Cu2O is an inherently p-type semiconductor with a direct bandgap of 2.17 eV [3] and high absorption coefficient of above 10 5 cm -1 in the visible region of the solar spectrum [4] which makes it a potential candidate as absorbers in solar cells. However, the highest practical efficiency of a solar cell with a Cu2O absorber achieved so far is only 8.1 % [5] even though the theoretical efficiency is around 18 % when referring to the Schockley-Queisser limit [6].…”

On Numerical Modelling and an Experimental Approach to Heterojunction Tandem Solar Cells Based on Si and Cu2O/ZnO—Results and Perspectives

“…Theoretically, the conversion efficiency of the copper oxide layer is 19%, but experimentally, a maximum conversion efficiency of only 8% has been obtained. A magnetron sputtering method was used to deposit Cu 2 O films on a quartz substrate [18][19][20][21][22]. The Cu target was placed in O 2/ Ar, and the substrate temperature was kept at 400 • C. Cu 2 O films with a thickness of around 500 nm were deposited at a rate of ~25 nm/min, then further annealed at 900 • C and p~0.1 Torr for 3 min.…”

“…A scanning electron microscope (SEM) equipped with an electron emission gun was used to investigate the morphology of the Cu 2 O film samples [22,23] with a resolution of 1.2 nm.…”

“…A magnetron sputtering method was used to deposit Cu2O films on a quartz substrat [18][19][20][21][22]. The Cu target was placed in O2/Ar, and the substrate temperature was kept at 40 °C.…”