Abstract
We have investigated the impact of Cu2ZnSnS4-Molybdenum (Mo) interface quality on the performance of sputter-grown Cu2ZnSnS4 (CZTS) solar cell. Thin film CZTS was deposited by sputter deposition technique using stoichiometry quaternary CZTS target. Formation of molybdenum sulphide (MoSx) interfacial layer is observed in sputter grown CZTS films after sulphurization. Thickness of MoSx layer is found ~142 nm when CZTS layer (550 nm thick) is sulphurized at 600 °C. Thickness of MoSx layer significantly increased to ~240 nm in case of thicker CZTS layer (650 nm) under similar sulphurization condition. We also observe that high temperature (600 °C) annealing suppress the elemental impurities (Cu, Zn, Sn) at interfacial layer. The amount of out-diffused Mo significantly varies with the change in sulphurization temperature. The out-diffused Mo into CZTS layer and reconstructed interfacial layer remarkably decreases series resistance and increases shunt resistance of the solar cell. The overall efficiency of the solar cell is improved by nearly five times when 600 °C sulphurized CZTS layer is applied in place of 500 °C sulphurized layer. Molybdenum and sulphur diffusion reconstruct the interface layer during heat treatment and play the major role in charge carrier dynamics of a photovoltaic device.
Highlights
Cu2ZnSnS4 (CZTS) is extensively studied as an active absorber layer in solar cell architecture as it is non-toxic, earth-abundant and has the potential to demonstrate excellent solar cell performance[1,2,3,4,5,6,7]
We demonstrate the impact of Mo out-diffusion and interface layer quality on the performance of sputter-grown CZTS based solar cells
The transient photovoltage (TPV) measurements were carried on the p-CZTS/n-CdS heterojunction solar cell to determine the photo-generated carrier lifetime using a pulsed Nd:YAG laser of wavelength 532 nm with the device illuminated with strong white light as background
Summary
Goutam Kumar Dalapati[1], Siarhei Zhuk[1,2], Saeid Masudy-Panah[1], Ajay Kushwaha[3], Hwee Leng Seng[1], Vijila Chellappan[1], Vignesh Suresh[1], Zhenghua Su4, Sudip Kumar Batabyal 5, Cheng Cheh Tan[1], Asim Guchhait[4], Lydia Helena Wong[4,6], Terence Kin Shun Wong2 & Sudhiranjan Tripathy[1]. We have investigated the impact of Cu2ZnSnS4-Molybdenum (Mo) interface quality on the performance of sputter-grown Cu2ZnSnS4 (CZTS) solar cell. Formation of molybdenum sulphide (MoSx) interfacial layer is observed in sputter grown CZTS films after sulphurization. We demonstrate the impact of Mo out-diffusion and interface layer quality on the performance of sputter-grown CZTS based solar cells. Since sulphur is present in the quaternary Cu2ZnSnS4 target; interfacial layer formation mechanism is different than the CZTS layer grown by sputter with multilayer layer metal films followed by sulphur annealing. In this work, the impact of Mo out-diffusion into CZTS films and formation of MoSx layer is addressed and solar cell performance is evaluated for the sputter-grown CZTS film. Scanning electron microscopy (SEM) was used to investigate the structural quality and interface layer thickness of sputter deposited CZTS thin film. The transient signals were fitted with a single exponential function in order to estimate the charge carrier lifetime
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