Band Gap Engineering of Alloyed Cu₂ZnGe_xSn_1–xQ₄ (Q = S,Se) Films for Solar Cell

Abstract

We fabricated polycrystalline Cu2ZnGe x Sn1–x Q4 (Q = S or Se) thin films by using spray-based deposition. The effects of Ge alloying were studied by X-ray diffraction (XRD), Raman spectroscopy, and UV–visible spectroscopy. XRD and Raman spectroscopy revealed that lattice parameters decreased linearly and characteristic Raman peaks shifted to higher frequency with increasing Ge alloying. The band gap energies of postsulfurized CZGTS films (1.51 ± 0.05 to 1.91 ± 0.05 eV) and postselenized CZGTSe films (1.07 ± 0.05 to 1.44 ± 0.05 eV) increased almost linearly with an increase of Ge alloying in the respective films. Analysis of band gap bowing model showed a small bowing constant b ∼ 0.1 ± 0.02 eV, indicating high miscibility of alloyed elements. The band gap tuning of CZGTS­(Se) thin films can be utilized for tuning band gap of subcell in multijunction cell and for band gap graded photoabsorber of high efficient solar cell.

Investigation of the structural, optical and electronic properties of Cu2Zn(Sn,Si/Ge)(S/Se)4alloys for solar cell applications

“…All studied compounds are direct-gap semiconductors. The relevant G-point gap energies are listed in Table 1, and the HSE06 values are in good agreement with available experimental and corresponding theoretical data [6,7,[12][13][14][15]22].…”

“…1 [6] and theoretical studies [7]. As expected, the lattice constants decrease monotonically and almost linearly for increasing Ge and Si-content because of the larger atomic covalent radius of Sn (1.45 Å) compared to those of Ge (1.25 Å) and Si (1.10 Å).…”

“…Incorporation of Ge or Si in CZTSSe has been suggested as one way to increase the PCE as well as the crystalline stability of high-quality CZTSSe [6][7][8][9][10][11][12]. For instance, by alloying Sn with Ge atoms in CZTSe, the band-gap energy of Cu 2 ZnSn 1Àx Ge x Se 4 can be varied from 1.1 to 1.45 eV when increasing x from 0 to 1 [6].…”

Band gap tuning of amorphous Al oxides by Zr alloying

“…4 Typically, a small value of the bowing parameter, and thus a small deviation from the linearity of the band gap of alloys, can indicate a good miscibility of the alloys, such as b ¼ 0.1, as estimated from polycrystalline CZGTS (Se) alloys. 20 A larger value of the bowing parameter, such as the one determined here and also reported for Al-Nb mixed oxides, indicates that the randomness in the alloys strongly influences the energy gap of the alloys. The compositional dependence of a band gap can originate from three distinct contributions: (i) change in the band structure due to change of the lattice constant upon alloying, (ii) modified atom positions with the internal structural relaxation of the bond lengths of the alloys, and (iii) charge exchange owing to different electronegativity of alloyed systems resulting in localized energy levels below the CBM.…”

Электрические и оптические свойства пленок Cu-=SUB=-2-=/SUB=-Zn(Fe,Mn)SnS-=SUB=-4-=/SUB=-, изготовленных спрей-пиролизом

“…Среди спо-собов изготовления пленок CZTS и Cu 2 MnSnS 4 (CMTS) метод спрей-пиролиза характеризуется простой реализа-цией, высокой мобильностью условий нанесения слоев и отсутствием сложного технологического оборудова-ния. Изготовленные с помощью метода спрей-пиролиза солнечные элементы на основе CZTS и CMTS име-ют эффективность ≥ 8% [11,[21][22][23]. В зависимости от условий проведения спрей-пиролиза (состав растворов, температурные и временные режимы пиролиза и т.…”