The Influence of Conduction Band Offset on CdTe Solar Cells

AbstractThe impact of the conduction band offset (CBO) between window/Cu(In,Ga)Se2 (CIGS) layers on the light soaking (LS) effect in CIGS solar cells has been studied with continuous CBO control using a (Zn,Mg)O (ZMO) window layer. Two types of CIGS solar cells with different window/buffer/absorber layers configurations were fabricated, i.e., ZMO/CIGS (without buffer layer) and ZMO/CdS/CIGS structures. The CBO values between ZMO and CIGS layers were controlled to -0.15~0.25 eV. Plus and minus signs of CBO indicate the conduction band minimums of ZMO above and below that of CIGS, respectively. Current-voltage (J-V) characteristics of the solar cells with different LS durations revealed that a positive CBO value higher than 0.16 eV induces J-V curve distortion, i.e., LS effect, and all the J-V characteristics stabilized in 30 min. The degrees of the LS effect were dominated by the CBO value between ZMO and CIGS layers in the both structure regardless of the existence of CdS buffer layers. These results indicate that the LS effect is dominated by the highest barrier for photo-generated electrons in the conduction band diagram, i.e., the CBO between ZMO and CIGS layers, and quantitatively the LS effect emerges the CBO value higher than 0.16 eV.

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Measurement of shunt resistance and conduction band offset in Cu(In, Ga)Se2 solar cells through joint analysis of temperature and intensity dependence of open-circuit voltage and photoluminescence

Japanese Journal of Applied Physics ◽

10.35848/1347-4065/ab89f8 ◽

2020 ◽

Vol 59 (5) ◽

pp. 055504

Author(s):

Craig H. Swartz ◽

Sanjoy Paul ◽

Lorelle M. Mansfield ◽

Jian V. Li ◽

Mark W. Holtz

Keyword(s):

Solar Cells ◽

Conduction Band ◽

Open Circuit Voltage ◽

Open Circuit ◽

Joint Analysis ◽

Band Offset ◽

Shunt Resistance ◽

Intensity Dependence ◽

Conduction Band Offset

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The Band Structures of Zn1−xMgxO(In) and the Simulation of CdTe Solar Cells with a Zn1−xMgxO(In) Window Layer by SCAPS

Energies ◽

10.3390/en12020291 ◽

2019 ◽

Vol 12 (2) ◽

pp. 291

Author(s):

Xu He ◽

Lili Wu ◽

Xia Hao ◽

Jingquan Zhang ◽

Chunxiu Li ◽

...

Keyword(s):

Solar Cells ◽

Band Gap ◽

Conduction Band ◽

Short Circuit ◽

Wavelength Region ◽

Short Circuit Current ◽

Window Layer ◽

Short Wavelength Region ◽

Conduction Band Offset ◽

Cdte Solar Cells

Wider band-gap window layers can enhance the transmission of sunlight in the short-wavelength region and improve the performance of CdTe solar cells. In this work, we investigated the band structure of In-doped Zn1−xMgxO (ZMO:In) by using first-principles calculations with the GGA + U method and simulated the performance of ZMO:In/CdTe devices using the SCAPS program. The calculation results show that with the increased Mg doping concentration, the band gap of ZMO increases. However, the band gap of ZMO was decreased after In incorporation due to the downwards shifted conduction band. Owing to the improved short circuit current and fill factor, the conversion efficiency of the ZMO:In-based solar cells show better performance as compared with the CdS-based ones. A highest efficiency of 19.63% could be achieved owing to the wider band gap of ZMO:In and the appropriate conduction band offset (CBO) of ~0.23 eV at ZMO:In/CdTe interface when the Mg concentration x approaches 0.0625. Further investigations on thickness suggest an appropriate thickness of ZMO:In (x = 0.0625) in order to obtain better device performance would be 70–100 nm. This work provides a theoretical guidance for designing and fabricating highly efficient CdTe solar cells.

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