Investigation of Properties Limiting Efficiency in Cu₂ZnSnSe₄-Based Solar Cells

Abstract

We have investigated different nonidealities in Cu 2 ZnSnSe 4 -CdS-ZnO solar cells with 9.7% conversion efficiency, in order to determine what is limiting the efficiency of these devices. Several nonidealities could be observed. A barrier of about 300 meV is present for electron flow at the absorber-buffer heterojunction leading to a strong crossover behavior between dark and illuminated current-voltage curves. In addition, a barrier of about 130 meV is present at the Mo-absorber contact, which could be reduced to 15 meV by inclusion of a TiN interlayer. Admittance spectroscopy results on the devices with the TiN backside contact show a defect level with an activation energy of 170 meV. Using all parameters extracted by the different characterization methods for simulations of the two-diode model including injection and recombination currents, we come to the conclusion that our devices are limited by the large recombination current in the depletion region. Potential fluctuations are present in the devices as well, but they do not seem to have a special degrading effect on the devices, besides a probable reduction in minority carrier lifetime through enhanced recombination through the band tail defects.

Variation of Quantum Efficiency in CZTSSe Solar Cells with Temperature and Bias Dependence by SCAPS Simulation

“…However, the reduction of quantum efficiency between 500-550 nm is milder than the other regions. This peculiar Q-E response occurs with a spike near 520-530 nm in the blue light region which is also reported in their measurements in literature [19,20]. …”

Spectral Responses in Quantum Efficiency of Emerging Kesterite Thin-Film Solar Cells

“…To be consistent with the reported literature, theories, or reasonable estimates, capture cross sections are fixed at 1.0 · 10 À12 cm 2 for electrons and 1.0 · 10 À15 cm 2 for holes at donor-type defect and at 1.0 · 10 À15 cm 2 for electrons and 1.0 · 10 À12 cm 2 for acceptor-type defect [12,[28][29][30][31][33][34][35][36][37]. For a comparative study of the ideal device in the previous section, the device structure is updated with very thin (5 nm) defective interface layer between CdS and CZTSSe.…”

“…This peculiar Q-E response occurs with a peak near 520-530 nm (in other words, near blue light region), reported at their measurements in Refs. [12,37].…”

Impact of pre-annealing temperature on the formation of Cu2ZnSnS4 absorber layer

“…For pure sulfide analog CZTS (Cu 2 ZnSnS 4 ) and for pure selenide analog CZTSe (Cu 2 ZnSnSe 4 ), the highest reported photochemical efficiencies are 8.4 and 9.7% respectively [5,6]. Doctor bladed CZTSSe solar cell has reported 7.5% efficiency which is quite encouraging [7].…”