Dominant recombination path in low-bandgap kesterite CZTSe(S) solar cells from red light induced metastability

Abstract

Hetero-junction kesterite Cu 2 ZnSn(S,Se) 4 solar cells with low bandgap obtained from three different methods of fabrication were exposed to red light illumination, and the changes observed in their electronic properties due to this exposure were studied via open circuit voltage transients, admittance spectroscopy, capacitance voltage profiling techniques, and SCAPS simulation fits to experimental data. The results from the aforementioned techniques, in combination with temperature-dependent current voltage analysis, can be used to reveal the dominant Shockley-Read-Hall recombination path at open circuit voltage. We also derived analytical expressions for the activation energy of the saturation current density and the diode quality factor for the specific case of a solar cell device that has no type inversion at the absorber/buffer interface and is limited by interface recombination in the open circuit condition. It is found that the dominant recombination pathway for the low bandgap Cu 2 ZnSn(S,Se) 4 solar cells under consideration is located in the space charge region and not at the absorber/buffer interface.

Exploring reverse-bias characteristics of CIGS solar cells: impact of alkali-post-deposition treatment and CdS buffer layer

“…This hypothesis could also explain why the two cell types with 20-nm and 30-nm buffers without PDT are affected much less by the photoexcitation of the buffer: Monitoring the V OC under red illumination over time reveals a decrease of the V OC transients in these two cell types (these measurements were done by colleagues at the Martin Luther University Halle-Wittenberg). This indicates that these cells are limited by interface recombination [25,26] (also seen in the V OC , cf. Tab.…”

Small Atom Doping: A Synergistic Strategy to Reduce SnZn Recombination Center Concentration in Cu2ZnSnSe4

“…It has been identified that for the Se-rich composition the main recombination pathways lie in the space-charge region (SCR), that is, in the bulk of the absorber. [14][15][16][17][18][19][20][21][22] Since the potential of kesterite materials as photovoltaic absorbers was identified, most of the publications have aimed to suppress the numerous detrimental effects of the proliferating secondary phases, while optimizing carrier concentration by controlling the Cu, Zn, Sn, and S/Se chemical potentials, that is, optimizing intrinsic doping. [23][24][25][26] This leads to constraints on the growth conditions to a compositional region where the impact of secondary phases is minimum.…”

“…It has been identified that for the Se‐rich composition the main recombination pathways lie in the space‐charge region (SCR), that is, in the bulk of the absorber. [ 14–22 ]…”