Intrinsic point defects and complexes in the quaternary kesterite semiconductorCu2ZnSnS4

Abstract

Current knowledge of the intrinsic defect properties of Cu 2 ZnSnS 4 ͑CZTS͒ is limited, which is hindering further improvement of the performance of CZTS-based solar cells. Here, we have performed first-principles calculations for a series of intrinsic defects and defect complexes in CZTS, from which we have the following observations. ͑i͒ It is important to control the elemental chemical potentials during crystal growth to avoid the formation of secondary phases such as ZnS, CuS, and Cu 2 SnS 3. ͑ii͒ The intrinsic p-type conductivity is attributed to the Cu Zn antisite which has a lower formation energy and relatively deeper acceptor level compared to the Cu vacancy. ͑iii͒ The low formation energy of many of the acceptor defects will lead to the intrinsic p-type character, i.e., n-type doping is very difficult in this system. ͑iv͒ The role of electrically neutral defect complexes is predicted to be important, because they have remarkably low formation energies and electronically passivate deep levels in the band gap. For example, ͓Cu Zn − +Zn Cu + ͔, ͓V Cu − +Zn Cu + ͔, and ͓Zn Sn 2− +2Zn Cu + ͔ may form easily in nonstoichiometric samples. The band alignment between Cu 2 ZnSnS 4 , CuInSe 2 and the solar-cell window layer CdS has also been calculated, revealing that a type-II band alignment exists for the CdS/ Cu 2 ZnSnS 4 heterojunction. The fundamental differences between CZTS and CuInSe 2 for use in thin-film photovoltaics are discussed. The results are expected to be relevant to other I 2-II-IV-VI 4 semiconductors.

Comparative study of the luminescence and intrinsic point defects in the kesterite Cu2ZnSnS4and chalcopyrite Cu(In,Ga)Se2Romero1, Du2, Teeter3 et al. 2011Phys. Rev. B20351220View full textAdd to dashboardCite

“…2). From first principles calculations [5], the copper-on-zinc antisite (Cu Zn ) is the dominant intrinsic point defect in CZTS with the lowest formation energy and an acceptor level at ε(- …”

“…In this regard, the kesterite Cu 2 ZnSnS 4 (CZTS) is attracting considerable interest because it contains all abundant elements Cu, Zn, Sn, and S and the reported bandgap is near the optimum for PV applications. First principles calculations predict that our understanding of the electronic structure and defect formation in the chalcopyrite structure of CIGS can be partly extrapolated to CZTS in the kesterite structure [4,5].…”

Structural diversity and electronic properties of Cu2SnX3(X=S, Se): A fir

“…[1][2][3][4][5][6] Due to the increased number of elements in the materials, their synthesis is relatively more difficult than for binary and ternary semiconductors 7,8 because more secondary phases like ZnS, Cu 2 SnS 3 (CTS), ZnSe and Cu 2 SnSe 3 (CTSe) may coexist in the samples. 9,10 The coexistence of these secondary phase compounds will inevitably influence the electrical and optical properties of CZTS and CZTSe samples, which have been observed experimentally and taken as the reason for the scattering of the measured properties.…”

A Cadmium-Free Cu2ZnSnS4/ZnO Hetrojunction Solar Cell Prepared by Practicable Processes

“…[4][5][6][7][8] Several research efforts have recently been made on the CZTS-based solar cells since Katagiri et al reported a CZTS/CdS hetrojunction solar cell with 6.77%. [9][10][11][12][13][14][15] However, an intensive usage of highly toxic cadmium compound such as CdS, prohibited by the RoHS (Restriction of the use of certain Hazardous Substances in electrical and electronic equipment) regulations, is a drawback and an alternative material is desirable to realize a more environment-friendly device.…”