Variable Light Soaking Effect of Cu(In,Ga)Se2 Solar Cells with Conduction Band Offset Control of Window/Cu(In,Ga)Se2 Layers

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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Explanation of Light/Dark Superposition Failure in CIGS Solar Cells

MRS Proceedings ◽

10.1557/proc-763-b5.20 ◽

2003 ◽

Vol 763 ◽

Cited By ~ 18

Author(s):

Markus Gloeckler ◽

Caroline R. Jenkins ◽

James R. Sites

Keyword(s):

Solar Cells ◽

Band Gap ◽

Red Light ◽

Window Layer ◽

Band Offset ◽

Conduction Band Offset ◽

Current Voltage ◽

In Series ◽

Cigs Solar Cells ◽

Photoinduced Changes

AbstractCIGS solar cells in many cases show a failure of light/dark superposition of their current-voltage (J-V) curves. Such failure generally becomes more pronounced at lower temperatures. J-V measurements under red light may also show an additional distortion, known historically as the “red kink”. The proposed explanation is that a secondary barrier results from the conduction band offset between CIGS and the commonly employed CdS window layer. This barrier produces a second diode with the same polarity and in series with the primary photodiode. The secondary-diode barrier height is modified by photoinduced changes of trap occupancy in the CdS layer, hence creating a voltage shift between dark and light conditions. Numerical modeling of the proposed explanation, including a band offset consistent with experimental and theoretical values, gives a very good fit to measured light and dark J-V curves over a wide temperature range. It also predicts the observed difference between illuminated J-V curves with photon energy above the CdS band gap, and those with sub-band-gap illumination.

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Conduction-Band-Offset Rule Governing J-V Distortion in CdS/CI(G)S Solar Cells

MRS Proceedings ◽

10.1557/proc-865-f5.32 ◽

2005 ◽

Vol 865 ◽

Cited By ~ 7

Author(s):

A. Kanevce ◽

M. Gloeckler ◽

A.O. Pudov ◽

J.R. Sites

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Conduction Band ◽

Defect Density ◽

Forward Bias ◽

Window Layer ◽

Band Offset ◽

Type I ◽

Current Collection ◽

Conduction Band Offset

AbstractA type-I (“spike”) conduction-band offset (CBO) greater than a few tenths of an eV at the n/p interface of a solar cell can lead to significant distortion of the current-voltage (J-V) curve. Such distortion has been observed in CdS/CIS cells, low-gallium CdS/CIGS cells, and CIGS cells with alternative windows that increase the CBO. The basic feature is reduced current collection in forward bias. The distortion is mitigated by photoconductivity in the CdS or other window layer, and it is therefore more severe if the illumination contains no photons with energies greater than the band gap of the window layer. The device-physics analysis of such distortion is numerical simulation incorporating a three-layer [TCO/CdS/CI(G)S] approximation for the solar cell. The parameters that influence the barrier height, and hence the distortion, are the magnitude of the CBO, the doping of the p- and n- layers, the defect density of the CdS, and the thicknesses of the CdS and TCO layers. The key value, however, is the energy difference between the quasi-Fermi level for electrons and the conduction band at the CdS/CIS interface. Thermionic emission across the interface will limit the current collection, if the difference exceeds approximately 0.48 eV at 300 K and one-sun illumination. This constraint is consistent with experiment, and strategies to satisfy the 0.48-eV rule when designing solar cells are enumerated.

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Co-solvent enhanced zinc oxysulfide buffer layers in Kesterite copper zinc tin selenide solar cells

Physical Chemistry Chemical Physics ◽

10.1039/c5cp01607j ◽

2015 ◽

Vol 17 (23) ◽

pp. 15355-15364 ◽

Cited By ~ 20

Author(s):

K. Xerxes Steirer ◽

Rebekah L. Garris ◽

Jian V. Li ◽

Michael J. Dzara ◽

Paul F. Ndione ◽

...

Keyword(s):

Solar Cells ◽

Buffer Layer ◽

Conduction Band ◽

Buffer Layers ◽

Band Offset ◽

Conduction Band Offset ◽

Tin Selenide ◽

Copper Zinc ◽

Zinc Oxysulfide

Performance deficiencies from the too large conduction band offset between Cu2ZnSnSe4/ZnOS heterojunctions are abated by the inclusion of a co-solvent during aqueous growth of the buffer layer.

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The Influence of Conduction Band Offset on CdTe Solar Cells

Journal of Electronic Materials ◽

10.1007/s11664-017-5850-9 ◽

2017 ◽

Vol 47 (2) ◽

pp. 1201-1207 ◽

Cited By ~ 8

Author(s):

Yunfei Chen ◽

Xuehai Tan ◽

Shou Peng ◽

Cao Xin ◽

Alan E. Delahoy ◽

...

Keyword(s):

Solar Cells ◽

Conduction Band ◽

Band Offset ◽

Conduction Band Offset ◽

Cdte Solar Cells

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Transport Properties and Conduction Band Offset of n-ZnO/n-6H-SiC Heterostructures

MRS Proceedings ◽

10.1557/proc-0957-k10-21 ◽

2006 ◽

Vol 957 ◽

Author(s):

Yahya Alivov ◽

Xiao Bo ◽

Fan Qian ◽

Daniel Johnstone ◽

Cole Litton ◽

...

Keyword(s):

Conduction Band ◽

Deep Level Transient Spectroscopy ◽

Deep Level ◽

Band Offset ◽

Measured Temperature ◽

Temperature Dependent ◽

Conduction Band Offset ◽

Current Voltage ◽

Current Voltage Characteristics ◽

Transient Spectroscopy

ABSTRACTThe conduction band offset of n-ZnO/n-6H-SiC heterostructures fabricated by rf-sputtered ZnO on commercial n-type 6H-SiC substrates has been measured. Temperature dependent current-voltage characteristics, photocapacitance, and deep level transient spectroscopy measurements showed the conduction band offsets to be 1.25 eV, 1.1 eV, and 1.22 eV, respectively.

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Degradation Mechanism Due to Water Ingress Effect on the Top Contact of Cu(In,Ga)Se2 Solar Cells

Energies ◽

10.3390/en13174545 ◽

2020 ◽

Vol 13 (17) ◽

pp. 4545

Author(s):

Deewakar Poudel ◽

Shankar Karki ◽

Benjamin Belfore ◽

Grace Rajan ◽

Sushma Swaraj Atluri ◽

...

Keyword(s):

Solar Cells ◽

Indium Tin Oxide ◽

Degradation Mechanism ◽

Transparent Conductive Oxide ◽

Window Layer ◽

Copper Indium Gallium Diselenide ◽

Copper Indium ◽

Cigs Solar Cells ◽

The Impact ◽

Secondary Ion

The impact of moisture ingress on the surface of copper indium gallium diselenide (CIGS) solar cells was studied. While industry-scale modules are encapsulated in specialized polymers and glass, over time, the glass can break and the encapsulant can degrade. During such conditions, water can potentially degrade the interior layers and decrease performance. The first layer the water will come in contact with is the transparent conductive oxide (TCO) layer. To simulate the impact of this moisture ingress, complete devices were immersed in deionized water. To identify the potential sources of degradation, a common window layer for CIGS devices—a bilayer of intrinsic zinc oxide (i-ZnO) and conductive indium tin oxide (ITO)—was deposited. The thin films were then analyzed both pre and post water soaking. To determine the extent of ingress, dynamic secondary ion mass spectroscopy (SIMS) was performed on completed devices to analyze impurity diffusion (predominantly sodium and potassium) in the devices. The results were compared to device measurements, and indicated a degradation of device efficiency (mostly fill factor, contrary to previous studies), potentially due to a modification of the alkali profile.

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