Explanation of Light/Dark Superposition Failure in CIGS Solar Cells

2003 ◽  
Vol 763 ◽  
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.

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

2007 ◽  
Vol 1012 ◽  
Author(s):  
Takashi Minemoto ◽  
Yasuhiro Hashimoto ◽  
Takuya Satoh ◽  
Takayuki Negami ◽  
Hideyuki Takakura
Keyword(s):  
Solar Cells ◽  
Conduction Band ◽  
Buffer Layers ◽  
Window Layer ◽  
Band Offset ◽  
Conduction Band Offset ◽  
Current Voltage ◽  
Variable Light ◽  
Cigs Solar Cells ◽  
The Impact

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.

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

Energies ◽  
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.

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

2005 ◽  
Vol 865 ◽  
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.

The Influence of Conduction Band Offset on CdTe Solar Cells

2017 ◽  
Vol 47 (2) ◽  
pp. 1201-1207 ◽  
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

Band gap optimization of the window layer in silicon heterojunction solar cells

Solar Energy ◽  
2014 ◽  
Vol 108 ◽  
pp. 570-575 ◽  
Author(s):  
C.L. Zhong ◽  
L.E. Luo ◽  
H.S. Tan ◽  
K.W. Geng
Keyword(s):  
Solar Cells ◽  
Band Gap ◽  
Window Layer ◽  
Heterojunction Solar Cells ◽  
Silicon Heterojunction Solar Cells

scholarly journals Silicon Heterojunction Solar Cells with p-Type Silicon Carbon Window Layer

Crystals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 402 ◽  
Author(s):  
Chia-Hsun Hsu ◽  
Xiao-Ying Zhang ◽  
Ming Jie Zhao ◽  
Hai-Jun Lin ◽  
Wen-Zhang Zhu ◽  
...  
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Band Gap ◽  
Flow Rate ◽  
Computer Aided Design ◽  
Hydrogenated Amorphous Silicon ◽  
Wavelength Region ◽  
Window Layer ◽  
Solar Cell Performance ◽  
Hydrogenated Amorphous

Boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) thin films are deposited using high frequency 27.12 MHz plasma enhanced chemical vapor deposition system as a window layer of silicon heterojunction (SHJ) solar cells. The CH4 gas flow rate is varied to deposit various a-SiC:H films, and the optical and electrical properties are investigated. The experimental results show that at the CH4 flow rate of 40 sccm the a-SiC:H has a high band gap of 2.1 eV and reduced absorption coefficients in the whole wavelength region, but the electrical conductivity deteriorates. The technology computer aided design simulation for SHJ devices reveal the band discontinuity at i/p interface when the a-SiC:H films are used. For fabricated SHJ solar cell performance, the highest conversion efficiency of 22.14%, which is 0.33% abs higher than that of conventional hydrogenated amorphous silicon window layer, can be obtained when the intermediate band gap (2 eV) a-SiC:H window layer is used.

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

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.

scholarly journals Characterization and Analysis of Ultrathin CIGS Films and Solar Cells Deposited by 3-Stage Process

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Grace Rajan ◽  
Krishna Aryal ◽  
Shankar Karki ◽  
Puruswottam Aryal ◽  
Robert W. Collins ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Large Scale ◽  
Open Circuit ◽  
Ex Situ ◽  
Photovoltaic Application ◽  
Current Voltage ◽  
Stage Process ◽  
Cigs Solar Cells ◽  
The Cost

In view of the large-scale utilization of Cu(In,Ga)Se2 (CIGS) solar cells for photovoltaic application, it is of interest not only to enhance the conversion efficiency but also to reduce the thickness of the CIGS absorber layer in order to reduce the cost and improve the solar cell manufacturing throughput. In situ and real-time spectroscopic ellipsometry (RTSE) has been used conjointly with ex situ characterizations to understand the properties of ultrathin CIGS films. This enables monitoring the growth process, analyzing the optical properties of the CIGS films during deposition, and extracting composition, film thickness, grain size, and surface roughness which can be corroborated with ex situ measurements. The fabricated devices were characterized using current voltage and quantum efficiency measurements and modeled using a 1-dimensional solar cell device simulator. An analysis of the diode parameters indicates that the efficiency of the thinnest cells was restricted not only by limited light absorption, as expected, but also by a low fill factor and open-circuit voltage, explained by an increased series resistance, reverse saturation current, and diode quality factor, associated with an increased trap density.

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