Controlling Band Alignment at the Back Interface of Cadmium Telluride Solar Cells using ZnTe and Te Buffer Layers

MRS Advances ◽  
2019 ◽  
Vol 4 (16) ◽  
pp. 913-919 ◽  
Author(s):  
Fadhil K. Alfadhili ◽  
Adam B. Phillips ◽  
Geethika K. Liyanage ◽  
Jacob M. Gibbs ◽  
Manoj K. Jamarkattel ◽  
...  
Keyword(s):  
Solar Cells ◽  
Fill Factor ◽  
Critical Role ◽  
Open Circuit ◽  
Band Alignment ◽  
Buffer Layers ◽  
Device Performance ◽  
Band Bending ◽  
Cdte Solar Cells ◽  
Hole Current

ABSTRACTFormation of a low barrier back contact plays a critical role in improving the photoconversion efficiency of the CdTe solar cells. Incorporating a buffer layer to minimize the band bending at the back of the CdTe device can significantly lower the barrier for the hole current, improving open circuit voltage (VOC) and the fill factor. Over the past years, researchers have incorporated the both ZnTe and Te as buffer layers to improve CdTe device performance. Here we compare device performance using these two materials as buffer layers at the back of CdTe devices. We show that using Te in contact to CdTe results in higher performance than using ZnTe in contact to the CdTe. Low temperature current density-voltage measurements show that Te results is a lower barrier with CdTe than ZnTe, indicating that Te has better band alignment, resulting in less downward bending in the CdTe at the back interface, than ZnTe does.

scholarly journals Enhancing the Performance of an Sb2Se3-Based Solar Cell by Dual Buffer Layer

2021 ◽  
Vol 13 (21) ◽  
pp. 12320
Author(s):  
Mamta ◽  
Kamlesh Kumar Maurya ◽  
Vidya Nand Singh
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Buffer Layer ◽  
Energy Band ◽  
Open Circuit ◽  
Band Alignment ◽  
Buffer Layers ◽  
Window Layer ◽  
Device Performance ◽  
Basic Parameters

In an Sb2Se3-based solar cell, the buffer layer is sandwiched between the absorber and the window layer, playing an essential role in interfacial electricity. Generally, CdS is used as a buffer layer, but its toxic nature and low bandgap can cause current loss because of parasitic absorption. In this work, we optimized the buffer layer by using ZnS as an alternative to the CdS buffer layer in order to decrease the use of CdS. The effect of different buffer layers on the solar device was explored by numerical simulation with the help of SCAPS 1D software. The basic parameters, such as open-circuit voltage (Voc), current density (Jsc), fill factor (FF), and efficiency (η) were analyzed and compared for both the buffer layers (CdS/ZnS). The results demonstrate that changing buffer materials and thicknesses has a significant impact on cell performance. The efficiency for the ZnS buffer layer was lower compared to that of the CdS-based solar cells because of insufficient energy band alignment. In order to enhance the efficiency of Sb2Se3-based solar cells, we used CdS/ZnS dual buffer layers and studied the device performance. The work function of the back contact also affects the device performance, and for work functions below 4.8 eV, the device’s efficiency was very low. The effect of varying the thicknesses and temperatures of the buffer layers on the I-V/C-V characteristics, quantum efficiency, and energy band structure are also reported. This study shall guide the researcher in reducing CdS and improving the device’s performance.

scholarly journals Ultra-low p-doping of poly(3-hexylthiophene) and its impact on polymer aggregation and photovoltaic performance

2016 ◽  
Vol 4 (1) ◽  
Author(s):  
Marcel M. Said ◽  
Yadong Zhang ◽  
Raghunath R. Dasari ◽  
Dalaver H. Anjum ◽  
Rahim Munir ◽  
...  
Keyword(s):  
Solar Cells ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Photovoltaic Performance ◽  
Photovoltaic Cells ◽  
Open Circuit ◽  
Device Performance ◽  
Long Range Order ◽  
P3ht Film ◽  
Low Levels

AbstractPoly(3-hexylthiophene) (P3HT) films and P3HT / fullerene photovoltaic cells have been p-doped with very low levels (< 1 wt. %) of molybdenum tris[1-(trifluoromethylcarbonyl)- 2-(trifluoromethyl)-ethane-1,2-dithiolene]. The dopants are inhomogenously distributed within doped P3HT films, both laterally and as a function of depth, and appear to aggregate in some instances. Doping also results in subtle changes in the local and long range order of the P3HT film. These effects likely contribute to the complexity of the observed evolutions in conductivity, mobility and work function with doping levels. They also negatively affect the open-circuit voltage and fill factor of solar cells in unexpected ways, indicating that dopant aggregation and non-uniform distribution can harm device performance.

scholarly journals The Effects of ZnTe:Cu Back Contact on the Performance of CdTe Nanocrystal Solar Cells with Inverted Structure

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 626 ◽  
Author(s):  
Bingchang Chen ◽  
Junhong Liu ◽  
Zexin Cai ◽  
Ao Xu ◽  
Xiaolin Liu ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Contact Layer ◽  
Open Circuit ◽  
Band Alignment ◽  
Device Performance ◽  
Back Contact ◽  
Device Structure ◽  
Inverted Structure ◽  
Cdte Nanocrystal

CdTe nanocrystal (NC) solar cells have received much attention in recent years due to their low cost and environmentally friendly fabrication process. Nowadays, the back contact is still the key issue for further improving device performance. It is well known that, in the case of CdTe thin-film solar cells prepared with the close-spaced sublimation (CSS) method, Cu-doped CdTe can drastically decrease the series resistance of CdTe solar cells and result in high device performance. However, there are still few reports on solution-processed CdTe NC solar cells with Cu-doped back contact. In this work, ZnTe:Cu or Cu:Au back contact layer (buffer layer) was deposited on the CdTe NC thin film by thermal evaporation and devices with inverted structure of ITO/ZnO/CdSe/CdTe/ZnTe:Cu (or Cu)/Au were fabricated and investigated. It was found that, comparing to an Au or Cu:Au device, the incorporation of ZnTe:Cu as a back contact layer can improve the open circuit voltage (Voc) and fill factor (FF) due to an optimized band alignment, which results in enhanced power conversion efficiency (PCE). By carefully optimizing the treatment of the ZnTe:Cu film (altering the film thickness and annealing temperature), an excellent PCE of 6.38% was obtained, which showed a 21.06% improvement compared with a device without ZnTe:Cu layer (with a device structure of ITO/ZnO/CdSe/CdTe/Au).

scholarly journals Improved Reliability of Small Molecule Organic Solar Cells by Double Anode Buffer Layers

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Pao-Hsun Huang ◽  
Chien-Jung Huang ◽  
Kan-Lin Chen ◽  
Jhong-Ciao Ke ◽  
Yeong-Her Wang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Small Molecule ◽  
Organic Solar Cells ◽  
Fill Factor ◽  
Copper Phthalocyanine ◽  
Open Circuit ◽  
Buffer Layers ◽  
Double Layers ◽  
Temperature And Pressure ◽  
Planar Heterojunction

An optimized hybrid planar heterojunction (PHJ) of small molecule organic solar cells (SM-OSCs) based on copper phthalocyanine (CuPc) as donor and fullerene (C60) as acceptor was fabricated, which obviously enhanced the performance of device by sequentially using both MoO3and pentacene as double anode buffer layers (ABL), also known as hole extraction layer (HEL). A series of the vacuum-deposited ABL, acting as an electron and exciton blocking layer, were examined for their characteristics in SM-OSCs. The performance and reliability were compared between conventional ITO/ABL/CuPc/C60/BCP/Ag cells and the new ITO/double ABL/CuPc/C60/BCP/Ag cells. The effect on the electrical properties of these materials was also investigated to obtain the optimal thickness of ABL. The comparison shows that the modified cell has an enhanced reliability compared to traditional cells. The improvement of lifetime was attributed to the idea of double layers to prevent humidity and oxygen from diffusing into the active layer. We demonstrated that the interfacial extraction layers are necessary to avoid degradation of device. That is to say, in normal temperature and pressure, a new avenue for the device within double buffer layers has exhibited the highest values of open circuit voltage (Voc), fill factor (FF), and lifetime in this work compared to monolayer of ABL.

scholarly journals p-Type Polymers for Templated Crystallization of Perovskite Films and Interface Optimization for High Performance Solar Cells

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 654
Author(s):  
Wei-Wei Zuo ◽  
Weifei Fu ◽  
Wan-Sheng Zong ◽  
Shen-Gang Xu ◽  
Ying-Liang Liu ◽  
...  
Keyword(s):  
Solar Cells ◽  
Charge Transfer ◽  
High Performance ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Device Performance ◽  
Phase Purity ◽  
Perovskite Material ◽  
P Type

The purity of the perovskite material is of paramount importance as it determines the optoelectronic properties and, hence, the device performance. However, the error during the experiment and incomplete crystallization is inevitable, leading to a low quality. Here, two p-type polymers were designed to template the crystallization of perovskite to obtain perovskite films with higher crystallinity and higher phase purity. The polymers at the perovskite/transport interface could also improve the charge transfer and, thus, the device performance. In this study, the highest efficiency device achieved an efficiency value of ~19% with improved open-circuit voltage and fill factor.

Correlation of the electronic structure of an interconnection unit with the device performance of tandem organic solar cells

2014 ◽  
Vol 2 (15) ◽  
pp. 5450-5454 ◽  
Author(s):  
Hyun-Sub Shim ◽  
Jung-Hung Chang ◽  
Seung-Jun Yoo ◽  
Chih-I. Wu ◽  
Jang-Joo Kim
Keyword(s):  
Electronic Structure ◽  
Solar Cells ◽  
Organic Solar Cells ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Device Performance

The electronic structure of an interconnection unit affects not only the open circuit voltage but also the fill factor in tandem organic solar cells.

P-layer Optimization in High Performance a-Si:H Solar Cells

2010 ◽  
Vol 1245 ◽  
Author(s):  
Yueqin Xu ◽  
Bill Nemeth ◽  
Falah Hasoon ◽  
Lusheng Hong ◽  
Anna Duda ◽  
...  
Keyword(s):  
Solar Cells ◽  
High Performance ◽  
Fill Factor ◽  
Transparent Conducting Oxide ◽  
Critical Role ◽  
Chemical Vapor ◽  
Open Circuit ◽  
Oxide Glass ◽  
Frequency Plasma ◽  
Hydrogenated Amorphous

AbstractWe report our progress toward high-performance hydrogenated amorphous silicon (a-Si:H) solar cells fabricated in NREL's newly installed multi-chamber film Si deposition system. The a-Si:H layers are made by standard radio frequency plasma-enhanced chemical vapor deposition. This system produces a-Si:H p-i-n single-junction devices on Asahi U-type transparent conducting oxide glass with >10% initial efficiency. The importance of the p-layer to the cell is identified: it plays a critical role in further improving cell performance. Our optimization process involves changing p-layer parameters such as dopant levels, bandgap, and thickness in cells as well as applying a double p-layer. With the optimized p-layer, we are able to increase the fill factor of our cells to as high as 72% while maintaining high open-circuit voltage.

scholarly journals Superstrate Structured FTO/TiO2/In2S3/Cu2ZnSnS4 Solar Cells Fabricated by a Spray Method with Aqueous Solutions

Coatings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 548 ◽  
Author(s):  
Dongho Lee ◽  
JungYup Yang
Keyword(s):  
Solar Cells ◽  
Fill Factor ◽  
Open Circuit ◽  
Absorber Layer ◽  
Buffer Layers ◽  
Window Layer ◽  
Spray Pyrolysis Method ◽  
Component Ratio ◽  
Tin Sulfide ◽  
Metallic Component

Copper Zinc Tin Sulfide (C2ZTS4) solar cells have become a fascinating research topic due to several advantages of the C2ZTS4 absorber layer, such as having non-toxic and abundantly available components. Superstrate structured C2ZTS4 solar cells were fabricated on the top of a fluorine-doped tin oxide (FTO) substrate with a spray pyrolysis method from the window layer to the absorber layer. Titanium dioxide (TiO2) and indium sulfide (In2S3) were used as the window and buffer layer, respectively. The source materials for the C2ZTS4 and buffer layers were all aqueous-based solutions. The metallic component ratio, Cu/(Zn + Sn), and the sulfur concentration in the solutions were systematically investigated. The optimum ratio of Cu/(Zn + Sn) in the film is about 0.785, while 0.18 M thiourea in the solution is the best condition for high performance. The C2ZTS4 layers deposited at lower temperatures (<360 °C) yielded a low quality resulting in low current density (JSC). On the other hand, the C2ZTS4 layers deposited at high temperature (~400 °C) showed a low fill factor (FF) without degradation of the open-circuit voltage (VOC) and JSC due to the junction degradation and high contact resistance between the absorber layer and metal contact. The best cell efficiency, VOC, JSC, and fill factor achieved were 3.34%, 383 mV, 24.6 mA/cm2, and 37.7%, respectively.

scholarly journals ALD-ZnMgO and absorber surface modifications to substitute CdS buffer layers in co-evaporated CIGSe solar cells

2020 ◽  
Vol 11 ◽  
pp. 12
Author(s):  
Ramis Hertwig ◽  
Shiro Nishiwaki ◽  
Mario Ochoa ◽  
Shih-Chi Yang ◽  
Thomas Feurer ◽  
...  
Keyword(s):  
Solar Cells ◽  
Buffer Layer ◽  
High Efficiency ◽  
Critical Role ◽  
Potassium Cyanide ◽  
Surface Preparation ◽  
Band Alignment ◽  
Buffer Layers ◽  
Layer Deposition ◽  
Absorber Surface

High efficiency chalcopyrite thin film solar cells generally use chemical bath deposited CdS as buffer layer. The transition to Cd-free buffer layers, ideally by dry deposition methods is required to decrease Cd waste, enable all vacuum processing and circumvent optical parasitic absorption losses. In this study, Zn1−xMgxO thin films were deposited by atomic layer deposition (ALD) as buffer layers on co-evaporated Cu(In,Ga)Se2 (CIGS) absorbers. A specific composition range was identified for a suitable conduction band alignment with the absorber surface. We elucidate the critical role of the CIGS surface preparation prior to the dry ALD process. Wet chemical surface treatments with potassium cyanide, ammonium hydroxide and thiourea prior to buffer layer deposition improved the device performances. Additional in-situ surface reducing treatments conducted immediately prior to Zn1−xMgxO deposition improved device performance and reproducibility. Devices were characterised by (temperature dependant) current-voltage and quantum efficiency measurements with and without light soaking treatment. The highest efficiency was measured to be 18%.

Microcrystalline (Si,Ge):H Solar Cells

2003 ◽  
Vol 762 ◽  
Author(s):  
Jianhua Zhu ◽  
Vikram L. Dalal
Keyword(s):  
Solar Cells ◽  
Buffer Layer ◽  
Quantum Efficiency ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Defect Density ◽  
Cell Structure ◽  
Open Circuit ◽  
Base Layer ◽  
Ecr Plasma

AbstractWe report on the growth and properties of microcrystalline Si:H and (Si,Ge):H solar cells on stainless steel substrates. The solar cells were grown using a remote, low pressure ECR plasma system. In order to crystallize (Si,Ge), much higher hydrogen dilution (∼40:1) had to be used compared to the case for mc-Si:H, where a dilution of 10:1 was adequate for crystallization. The solar cell structure was of the p+nn+ type, with light entering the p+ layer. It was found that it was advantageous to use a thin a-Si:H buffer layer at the back of the cells in order to reduce shunt density and improve the performance of the cells. A graded gap buffer layer was used at the p+n interface so as to improve the open-circuit voltage and fill factor. The open circuit voltage and fill factor decreased as the Ge content increased. Quantum efficiency measurements indicated that the device was indeed microcrystalline and followed the absorption characteristics of crystalline ( Si,Ge). As the Ge content increased, quantum efficiency in the infrared increased. X-ray measurements of films indicated grain sizes of ∼ 10nm. EDAX measurements were used to measure the Ge content in the films and devices. Capacitance measurements at low frequencies ( ~100 Hz and 1 kHz) indicated that the base layer was indeed behaving as a crystalline material, with classical C(V) curves. The defect density varied between 1x1016 to 2x1017/cm3, with higher defects indicated as the Ge concentration increased.

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