Multiple phases of Cu2ZnSnSe4 detected by room temperature photoluminescence (vol 116, 073509, 2014)

in JOURNAL OF APPLIED PHYSICS (2015), 118(8),

Different Bandgaps in Cu2ZnSnSe4: A High Temperature Coevaporation Study

in IEEE Journal of Photovoltaics (2015), 5(2), 641-648

We present a high-temperature Cu2ZnSnSe4 coevaporation study, where solar cells with a power conversion efficiency of 7.1 have been achieved. The process is monitored with laser light scattering in order ... [more ▼]

We present a high-temperature Cu2ZnSnSe4 coevaporation study, where solar cells with a power conversion efficiency of 7.1 have been achieved. The process is monitored with laser light scattering in order to follow the incorporation of the Sn into the film. We observe the segregation of ZnSe at the Mo/CZTSe interface. Optical analysis has been carried out with photoluminescence and spectrophotometry. We observe strong band tailing and a bandgap, which is significantly lower than in other reported efficient CZTSe absorbers. The photoluminescence at room temperature is lower than the bandgap due to the existence of a large quantity of tail states. Finally, we present effects of low-temperature postannealing of the absorbers on ordering of the Cu/Zn atoms in CZTSe and solar cell parameters. We observe strong changes in all solar cell parameters upon annealing. The efficiency of the annealed devices is significantly reduced, although ordering is improved compared with ones made from nonannealed absorbers. [less ▲]

Cu2ZnSnSe4 thin film solar cells produced via co-evaporation and annealing including a SnSe2 capping layer

in PROGRESS IN PHOTOVOLTAICS (2014), 22(1), 51-57

Cu2ZnSnSe4 (CZTSe) thin film solar cells have been produced via co-evaporation followed by a high-temperature annealing. In order to reduce the decomposition of the CZTSe, a SnSe2 capping layer has been ... [more ▼]

Cu2ZnSnSe4 (CZTSe) thin film solar cells have been produced via co-evaporation followed by a high-temperature annealing. In order to reduce the decomposition of the CZTSe, a SnSe2 capping layer has been evaporated onto the absorber prior to the high-temperature treatment. This eliminates the Sn losses due to SnSe evaporation. A solar cell efficiency of 5.1 could be achieved with this method. Moreover, the device does not suffer from high series resistance, and the dominant recombination pathway is situated in the absorber bulk. Finally different illumination conditions (white light, red light, and yellow light) reveal a strong loss in fill factor if no carriers are generated in the CdS buffer layer. This effect, known as red-kink effect, has also been observed in the closely related Cu(In,Ga)Se-2 thin film solar cells. Copyright (c) 2013 John Wiley Sons, Ltd. [less ▲]