Adjusting the SnZn defects in Cu2ZnSn(S,Se)4 absorber layer via Ge4+ implanting for efficient kesterite solar cells

Relevance of Ge incorporation to control the physical behaviour of point defects in kesterite

“…Using deep-level transient spectroscopy, Deng et al reported a defect activation energy of 0.581 eV for the Sn-based kesterite, and identied this defect as a recombination centre. 36 As shown in Fig. 5a and in agreement with this experimental observation, this defect could be reported as the substitutional defect Sn Zn with its two-electron transition level (+2/0) at 0.584 eV above the VBM.…”

“…3,[18][19][20][21][22][23] Both theoretical and experimental approaches have been used. A wide range of cationic substitutions have been investigated: Cu by Ag, 24,25 Zn by Cd, 24,[26][27][28] Sn by Ge, [28][29][30][31][32] S by Se 4 and doping of both Cu 2 -ZnSnS 4 and Cu 2 ZnSnSe 4 by Na, Li, Ga 33 and Ge 18,[34][35][36] or even using more exotic elements as in ref. 20 .…”

“…31 In a recent study, Deng et al demonstrated experimentally that Ge 4+ can be introduced in Cu 2 ZnSnS 4 to suppress the detrimental deep Sn Zn defects. 36 In addition, compared to Cu 2 ZnSnS 4 , pure Ge-kesterite absorber layers present a larger band gap value which limits the maximal single solar cell efficiency. 40 Nevertheless, Ge alloying could be used for the synthesis of wide band gap kesterite which is of high interest for top cells in a tandem approach.…”

Passivation principle of deep-level defects: a study of SnZn defects in kesterites for high-efficient solar cells

“…However, the band-tail states caused by the energetically favorable 2Cu Zn + Sn Zn defect complex are still serious. Recently, it was found experimentally that partially replacing Sn 4+ with Ge 4+ can suppress the deep-levels and improve the V oc of kesterites, 21 while the increased bandgap and the localized bottom of the conduction band (CB) caused by the Ge-4p orbital are unfavorable to the optical absorption and the minority carrier transport. Therefore, the adverse effects induced by Sn Zn defects have not been properly addressed either by adjusting the chemical potentials or substituting elements.…”

Relevance of Ge incorporation to control the physical behaviour of point defects in kesterite

“…Both theoretical and experimental approaches have been used. A wide range of cationic substitutions have been investigated: Cu by Ag [22], Zn by Cd [23,22], Sn by Ge [24,25,26,27], S by Se [28] and doping of both Cu 2 ZnSnS 4 and Cu 2 ZnSnSe 4 by Na, Li, Ga [29] and Ge [30,31,32,17] or even using more exotic elements as in Ref. [19].…”