Zn1-xMgxO: Band Structure and Simulation as Window Layer for CdTe Solar Cell by SCAPS Software

doi:10.15541/jim20170349

Abstract

Abstract:

In this paper, the band structure of Zn_1-_xMg_xO(ZMO) alloy with different Mg compositions by using first-principles calculations with GGA+U method was studied. The calculation results show that position of conduction band offset and Fermi level of Zn_1-_xMg_xO move towards the vacuum level while the band gap becomes wider with the increasing Mg concentration. Based on theoretical calculation results of ZMO, ZMO/CdTe, CdS/CdTe solar cells were modeled using SCAPS software and its device performances were simulated and analyzed in detail. The results indicate that the conversion efficiency of CdTe solar cell with ZMO is higher than that of solar cell with CdS due to the high open circuit voltage and short circuit current density when x in Zn_1-_xMg_xO is in the range of 0-0.125. Efficiency of CdTe solar cells with ZMO reaches 18.29% because the recombination decreases obviously resulting from appropriate conduction band offset about 0.13 eV at ZMO/CdTe interface. These data provide a theoretical guidance for design and fabrication of high efficiency CdTe solar cells.

Key words: Zn_1-_xMg_xO, band structure, solar cell, conversion efficiency

CLC Number:

O447

HE Xu, REN Sheng-Qiang, LI Chun-Xiu, WU Li-Li, ZHANG Jing-Quan, DU Zheng. Zn_1-_xMg_xO: Band Structure and Simulation as Window Layer for CdTe Solar Cell by SCAPS Software[J]. Journal of Inorganic Materials, 2018, 33(6): 635-640.

Figures/Tables 11

References 26

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Layer properties	FTO	CdS	Zn_1-_xMg_xO					CdTe	ZnTe:Cu
Layer properties	FTO	CdS	x=0	x=0.0625	x=0.125	x=0.1875	x=0.25	CdTe	ZnTe:Cu
ε/ε₀	8.9	9.0	9.0	9.0	9.0	9.0	9.0	10.0	10.1
N_c/cm^-3	5.2×10¹⁸	2.2×10¹⁸	4.0×10¹⁸	10¹⁷	9.0×10¹⁶	10¹⁶	10¹⁵	9.2×10¹⁷	1.5×10¹⁸
N_v/cm^-3	10¹⁹	1.80×10¹⁹	9.00×10¹⁸	10¹⁸	9.00×10¹⁷	10¹⁷	10¹⁶	5.20×10¹⁸	1.16×10¹⁹
μ_n/(cm²˖V^-1˖s^-1)	100	340	50	50	50	50	50	400	400
μ_p/(cm²˖V^-1˖s^-1)	25	50	20	20	20	20	20	60	50
N_A/cm^-3	10²⁰	10¹⁷	5.0×10¹⁷	10¹⁶	9.0×10¹⁵	10¹⁵	9.0×10¹⁴	1.5×10¹⁴	1.5×10²⁰
Thickness/nm	3.5×10²	10²	10²	10²	10²	10²	10²	5.0×10³	70.0

Layer properties	FTO	CdS	Zn_1-_xMg_xO					CdTe	ZnTe:Cu
Layer properties	FTO	CdS	x=0	x=0.0625	x=0.125	x=0.1875	x=0.25	CdTe	ZnTe:Cu
ε/ε₀	8.9	9.0	9.0	9.0	9.0	9.0	9.0	10.0	10.1
N_c/cm^-3	5.2×10¹⁸	2.2×10¹⁸	4.0×10¹⁸	10¹⁷	9.0×10¹⁶	10¹⁶	10¹⁵	9.2×10¹⁷	1.5×10¹⁸
N_v/cm^-3	10¹⁹	1.80×10¹⁹	9.00×10¹⁸	10¹⁸	9.00×10¹⁷	10¹⁷	10¹⁶	5.20×10¹⁸	1.16×10¹⁹
μ_n/(cm²˖V^-1˖s^-1)	100	340	50	50	50	50	50	400	400
μ_p/(cm²˖V^-1˖s^-1)	25	50	20	20	20	20	20	60	50
N_A/cm^-3	10²⁰	10¹⁷	5.0×10¹⁷	10¹⁶	9.0×10¹⁵	10¹⁵	9.0×10¹⁴	1.5×10¹⁴	1.5×10²⁰
Thickness/nm	3.5×10²	10²	10²	10²	10²	10²	10²	5.0×10³	70.0

x	ΔE_c/eV	E_g/eV	E_f/eV	χ/eV	φ/eV
0	-0.03	3.32	2.48	4.53	5.31
0.0625	0.06	3.41	2.53	4.44	5.18
0.125	0.13	3.48	2.86	4.37	4.99
0.1875	0.29	3.65	2.91	4.21	4.84
0.25	0.47	3.82	3.02	4.03	4.83

x	ΔE_c/eV	E_g/eV	E_f/eV	χ/eV	φ/eV
0	-0.03	3.32	2.48	4.53	5.31
0.0625	0.06	3.41	2.53	4.44	5.18
0.125	0.13	3.48	2.86	4.37	4.99
0.1875	0.29	3.65	2.91	4.21	4.84
0.25	0.47	3.82	3.02	4.03	4.83

	CdS	Zn_1-_xMg_xO
	CdS	x=0	x=0.0625	x=0.125	x=0.1875	x=0.25
V_oc/mV	821	825	829	837	838	928
J_sc/(mA•cm^-2)	24.34	27.88	28.22	28.36	27.95	0.20
FF/%	75.32	75.08	76.77	77.02	53.05	8.27
η/%	15.06	17.28	17.98	18.29	12.42	0.01