Ge-alloyed kesterite thin-film solar cells: previous investigations and current status – a comprehensive review

Abstract

Ge alloying in kesterite thin films enables to mitigate electronic defect and disorder, enhance morphology as well as realize bandgap grading, all contributing to higher performance of complete solar cells via resolved Voc and fill factor deficits.

Progress and Prospects with Cationic and Anionic Doping of Solution-Processed Kesterite Solar Absorbers: A Mini-Review

“…It enables Sn−Ge bandgap grading to improve carrier collection and increase J SC . 64 By substituting Ge, an increase in the bandgap energy, carrier collection, and decrease in V OC deficit are observed. 42,44 The evolution of structure from tetragonal CZTS to orthorhombic CZGS with an increase in the Ge/Sn ratio as reported is shown in Figure 1c.…”

“…Thus, Ge is a promising candidate for incorporation into kesterite. 64 Incorporation of Cd varied the defect characteristics that can occur in the acceptor states near the valence band, and the addition of Ag reduced the recombination of carriers. Figure 1a represents the device structure of ACZCTS, and Figure 1b shows the dark and light J−V characteristics of the ACZCTS device.…”

“…Ge doping significantly reduces the crystalline disorder and electronic defects to lower the V OC deficit of the CZTSSe device. Thus, Ge is a promising candidate for incorporation into kesterite …”

Semitransparent Wide Bandgap Cu2ZnGe(S,Se)4Thin‐Film Solar Cells: Role of the Sulfurization Process

“…Efforts to enhance the performance of CZTSSe are focused toward the reduction of the large open-circuit voltage (V OC ) deficit that are mainly caused by heterojunction interface recombination (kesterite/CdS); optimization of the bulk of the absorber bandgap and potential fluctuations induced by Cu-Zn crystalline disorder; [2] and the presence of secondary phases, among other factors. [3,4] The introduction of Ag or Ge has led to the reduction of some specific defects. [3][4][5] As a result of these efforts recently, efficiencies higher than 14 % have been achieved for Ag-alloyed CZTSSebased solar cells.…”

Improving the Device Performance of CZTSSe Thin-Film Solar Cells via Indium Doping

“…In recent times, various cations (Na, Ag, Ge, Cd, In, Mg, Sb, etc.) have been introduced within the CZTSSe absorber layer and showed their positive impact on the device performance of kesterite TFSCs. ,− Between them, In is the most attractive doping element, as it can reside in multiple locations in the CZTSSe host crystal structure. When In takes the place of Zn or Sn, it creates charged defects since the In charge has a +3 state, while Sn is +4 and Zn is a + 2 state.…”