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We carried out electrical and impedance studies on solution derived Al:ZnO/ZnO/CdS/Cu2ZnSnS4/Mo/Glass multilayered solar cell structures to understand their impact on photovoltaic performance. The Cu2ZnSnS4 layer is synthesized on a molybdenum (Mo) coated soda lime glass substrate as an absorber and characterized intensively to optimize the absorber physical properties. The optimized Cu2ZnSnS4 is p-type with 5.8 × 1017 cm−3 hole carrier concentration. The depletion width of the junction is around 20.5 nm and the diffusion capacitance is ∼35.5 nF for these devices. We observed relatively large minority carrier life time ∼23 μs for these structures using open voltage decay analysis. The measured Cu2ZnSnS4/MoS2 and Cu2ZnSnS4/CdS interface resistances are 7.6 kΩ and 12.5 kΩ, respectively. The spatial inhomogeneities are considered and the corresponding resistance is ∼11.4 kΩ. The impedance measurements suggest that in conjunction with series resistance ∼350 Ω, the interface and spatial inhomogeneity resistances also give a significant contribution to the photovoltaic performance.

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Quaternary compound semiconductor Cu2ZnSnS4 (CZTS) has been prepared using two different precursors sols, chlorides and nitrates, using spin coating process to get phase pure and less defective thin films for solar photovoltaics. The synthesized CZTS thin films are heat treated at different temperatures to achieve the kesterite crystallographic phase. The prepared thin films are highly textured along (112) axis. The surface microscopic images suggest that chloride precursor derived CZTS thin films are relatively uniform and densely packed as compared to nitrate precursors. The dislocation density is ∼1 × 1016 lines m−2 for the chloride precursor derived thin films, much lower than that of the nitride precursor derived CZTS thin films. The optical absorption measurements suggest the direct optical gap ∼1.52 eV for CZTS thin films derived from both the precursor routes. However, electrical resistivity measurements suggest that resistivity is uniform and much lower ∼0.025 Ω cm for chloride precursor CZTS thin films, alike nitride precursor CZTS thin films, where resistivity is three orders of magnitude higher ∼30 Ω cm. These studies suggest that chloride precursor derived CZTS thin films are of high quality and can be used for solar photovoltaic applications.

Transition metal dichalcogenides based materials exhibit promising optoelectronic properties for solar cell application. We considered the heterostructure single junction solar cell with bulk W­(S/Se)2 as an absorber material and ultrathin Janus WSeTe layer as a buffer layer. The optoelectronic properties of WSeTe monolayer are calculated using density functional theory calculations. The high absorption coefficient of WS2/WSe2 makes them suitable absorber materials. The performance of layered single junction heterostructure is simulated using SCAPS-1D simulator. The device performance is evaluated to understand the effect of an absorber layer thickness, carrier concentration, defect density, work function, buffer layer carrier concentration, and interface defect density. After optimization of all the possible parameters, the maximum efficiencies noted are 18.87% and 18.1% for AZO/WSeTe/WS2 and AZO/WSeTe/WSe2 solar cells, respectively.