Screening of suitable cationic dopants for solar absorber material CZTS/Se: A first principles study

Abstract

The earth abundant and non-toxic solar absorber material kesterite Cu2ZnSn(S/Se)4 has been studied to achieve high power conversion efficiency beyond various limitations, such as secondary phases, antisite defects, band gap adjustment and microstructure. To alleviate these hurdles, we employed screening based approach to find suitable cationic dopant that can promote the current density and the theoretical maximum upper limit of the energy conversion efficiency (P(%)) of CZTS/Se solar devices. For this task, the hybrid functional (Heyd, Scuseria and Ernzerhof, HSE06) were used to study the electronic and optical properties of cation (Al, Sb, Ga, Ba) doped CZTS/Se. Our in-depth investigation reveals that the Sb atom is suitable dopant of CZTS/CZTSe and also it has comparable bulk modulus as of pure material. The optical absorption coefficient of Sb doped CZTS/Se is considerably larger than the pure materials because of easy formation of visible range exciton due to the presence of defect state below the Fermi level, which leads to an increase in the current density and P(%). Our results demonstrate that the lower formation energy, preferable energy gap and excellent optical absorption of the Sb doped CZTS/Se make it potential component for relatively high efficient solar cells.

Defect Engineering in Earth‐Abundant Cu2ZnSn(S,Se)4 Photovoltaic Materials via Ga3+‐Doping for over 12% Efficient Solar Cells

“…According to the previous theoretical calculation, the lattice parameters of Ga‐doped CZTS/Se are almost identical to the pure CZTS/Se, in which a = 10.94/11.53 Å for pure CZTS/Se and a = 10.97/11.54 Å for Ga‐doped CZTS/Se. [ 38 ] There are no shifts in peak positions for the samples with different Ga‐doping levels in our XRD results, which is consistent with the theoretical results. Furthermore, Raman scattering using different excitation wavelengths (532, 325, and 633 nm) were performed as an auxiliary method to detect any possible coexisting secondary phases, as displayed in Figure 4f and Figure S6, Supporting Information.…”

Numerical modelling of ion-migration caused hysteresis in perovskite solar cells

“…The hysteresis is related to non-identical I-V characteristic in forward and reverse scan. This peculiar observation is somehow special to hybrid organic-inorganic perovskite material, other material like dye sensitized, quantum dot, organic and inorganic solar cells do not have such observations (Jyothirmai et al 2019;Prasad et al 2018;Karuthedath et al 2019;Maity et al 2019;Kumar et al 2018. Hysteresis is a persistent observation in perovskite solar cells, although it does not hinder performance and efficiency it represents complex material physics and device working.…”

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

“…Over the recent years, attempts have been made to circumvent these actual limitations using alloying and doping of kesterite materials with other elements. 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.…”

“…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 . Some of these substitutions resulted in cell efficiencies as large as 12.3% as in the case of Ga or Ge doping.…”

“…Moreover, although several material modelling studies have focused on the physical behaviour of defects in kesterite compounds, 6,7,20,33 only a few studies have been dedicated so far to Ge compounds. 28,41,42 To ll this void, in this work, we report the investigation of point defects in both Cu 2 ZnSnS 4 and Cu 2 -ZnGeS 4 .…”