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Type Literature review
Authors Mehdi Malekrah
Published 2019
License CC-BY-SA-4.0
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Note[edit | edit source]

This is a literature review page to take optical and electrical parameters from existing 2D PV devices at the lab scale and scale them up to make a theoretical module. Then do simulation on them e.g. AOI, antireflection coating etc. in something like pvlib to provide system designers with the new module. It would be our pleasure if you share your experience in this area with us. (Discussion tab is top left of this page)

Background[edit | edit source]

Electric Field Effect in Atomically Thin Carbon Films [1][edit | edit source]

What is a 2D material?: 2D materials refer to crystalline, generally single atom thin materials which are covalently bonded (in plane bonding) to perform a strong single layer and then weakly bonded, generally Van der Waals bonding, to the next layer (out of plane bonding) to make it easy to exfoliate from each other without destroying the single layer crystalline structure. 2D material can be made of one element or a compound of two or more elements. Graphene (single layer of graphite) is the first and the most studied 2D material. Although Graphene was explored first by Wallance in 1947 however it never been physically made till 2004 by Novoselov and Geim who won a Physics noble prize for this discovery. Geim used mechanical exfoliation technique using scotch tape to separate graphite layers to end up by single layer graphene.

  • Few Layer Graphene (FLG) size was up to 10 um and for thicker film ~ 3nm size reached to 100 um
  • FLG were put into multiterminal Hall bar devices on top of SiO2 and applied Vg to investigate electronic properties
  • Dependence of resistivity on Vg and charge transport is being done by Shubnikov-de Haas (ShdH) oscillations studies

Electronics based on two-dimensional materials [2][edit | edit source]

Abstract The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal–oxide–semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.

Literature Review[edit | edit source]

The reflectivity spectra of some group VA transition metal dichalcogenides [3][edit | edit source]

Abstract: This paper investigate reflectivity spectra from basal planes of these crystal structure of VA TMDCs; 2H-NbSe2, 2H-Tase2, 2H-TaS2 and 1T-TaS2 for energy range between 25 meV and 14 eV in two different temperature room temperature and 77K. In continue they did Kramers-Kronig analysis and band band models for these materials discussed. 2H-NbSe2, 2H-Tase2, 2H-TaS2 are metallic because half filled d band and 1T-TaS2 showing semiconductor behavior at room T.

  • reflectivity spectra measured for all 4 materials from 0.025 eV to 30 eV at room temp and 77K
  • very sharp peak measured for all 4 materials in low energy (<2eV)
  • Optical parameters of all 4 materials provided

1.real and imaginary parts of dielectric function at room temperature

2.real and imaginary parts of dielectric function at 77 K

3.absorption coefficient

4.energy-loss function

5.oscillator sum integral neff(E)

Electrodeposited semiconducting molybdenum selenide films. II. Optical, electrical, electrochemical and photoelectrochemical solar cell studies [4][edit | edit source]

Abstract: MoSe2 was electrodeposited and optical, electrical and electrochemical behaviors studied. optical absorption defined an indirect bandgap material with BG=1.14 eV. Electrical conductivity at various T showed impurity conduction and existance of deep level traps. Mott-Schottky plots for type of semiconductor and parameters like ND, Ec and Ev. the J-V graphs from electrochemical studies show charge transfer at interface is due valence band and it also involves surface states. They use electrodeposition to deposit MoSe2 in fabrication of photoelectrochemical solar cell. In this type of solar cell charge transfer take place at semiconductor- electrolyte interface and produce photocurrent. Films deposited on conducting glass plates to study optical absorption behavior.

  • optical absorption graph showed very broad peaks because electrodeposited is polycrystalline and weak absorption because of thin layer (1.1 um). absorption spectra confirm indirect spectra
  • Film deposited on Ti substrate as back contact and silver dots for front contact studied for Electrical conductivity. They performed ohmic contact
  • I-V curve shows linear behavior (Ohm's law) for lower voltages which become nonlinear for higher voltages after filling of a discrete set of traps.
  • Electrochemical characterization showed n-type behavior ND= 10 e15
  • The efficiency of this solar cell was measured very low because of these reasons (1)Low film thickness (1.1 um) causing small number of e-h pairs. (2) existance of high density traps at the surface and deep (3) film was not uniform

* They used a multilayer film of MoSe2 so in result was an indirect material (direct bandgap behavior was not discovered yet)Italic text

MS2 (M = W, Mo) photosensitive thin films for solar cells [5][edit | edit source]

Abstract: WS2 and MoS2 photosensitive films deposited by sputtering on 10-20 nm thick Ni layer and then crystallization process by annealing at 1073K for 30min. two different technique for film deposition ; MoS2: Solid State Reaction WS2: reactive sputtering

  • X-ray diffraction pattern for both films obtained indicating basal plane crystalline with a sharp peak
  • XPS spectra for both films studied
  • Optical absorption spectra and photoconductivity for both films studied
  • analyzing all data showed film properties was independent to deposition technique and thin layer of Ni and annealing on 1073 K played the most important role to make poly crystalline structure with big enough grain boundaries to obtain photocurrent. Thin Ni layer caused Metal Induced Crystallization process I believe It also made a textured pattern on the surface

Graphene‐On‐Silicon Schottky Junction Solar Cells [6][edit | edit source]

Abstract:

  • Deposit Graphene Sheets (GS) on n-Si wafer with average PCE 1.5%
  • multilayer graphene to reach higher mobility
  • GS form a Schottky junction with n-Si
  • GS work also as ARC with reducing reflection 70% visible and 80% near IR
  • efficiency drops with thicker film, more recombination occurs
  • there is a trade off between conductivity and transparency

Monolayer graphene film/silicon nanowire array Schottky junction solar cells [7][edit | edit source]

Abstract: Schottky junction solar cells were constructed by combining the monolayer graphene (MLG) films and the Si nanowire (SiNW) arrays. Pronounced photovoltaic characteristics were investigated for devices with both p-MLG/n-SiNWs and n-MLG/p-SiNWs structures. Due to the balance between light absorption and surface carrier recombination, devices made of SiNW arrays with a medium length showed better performance and could be further improved by enhancing the MLG conductivity via appropriate surface treatment or doping. Eventually, a photoconversion efficiency up to 2.15% is obtained by the means of filling the interspace of SiNW array with graphene suspension.

  • 8 different structure examined, highest PCE= 2.15% with garaphene suspension filling the gaps between NWs
  • Table 1 in the page 133113-2 summarize all 8 different structures

Graphene based Schottky junction solar cells on patterned silicon-pillar-array substrate [8][edit | edit source]

Abstract: Graphene-on-silicon Schottky junction solar cells were prepared with pillar-array-patterned silicon substrate. Such patterned substrate showed an anti-reflective characteristic and led to an absorption enhancement of the solar cell, which showed enhanced performance with short-circuit current density, open-circuit voltage, fill factor, and energy conversion efficiency of 464.86 mV, 14.58 mA/cm2, 0.29, and 1.96%, respectively. Nitric acid was used to dope graphene film and the cell performance showed a great improvement with efficiency increasing to 3.55%. This is due to the p-type chemical doping effect of HNO3 which increases the work function and the carrier density of graphene.

  • Chemical doping of graphene
  • They showed doping of graphene by HNO3 for 15s enhance the PCE from 1.96% to 3.55%
  • Table I in the page 233505-2 summarize all experimental data

High Efficiency Graphene Solar Cells by Chemical Doping [9] [edit | edit source]

Abstract: We demonstrate single layer graphene/n-Si Schottky junction solar cells that under AM1.5 illumination exhibit a power conversion efficiency (PCE) of 8.6%. This performance, achieved by doping the graphene with bis(trifluoromethanesulfonyl)amide, exceeds the native (undoped) device performance by a factor of 4.5 and is the highest PCE reported for graphene-based solar cells to date. Current−voltage, capacitance−voltage, and external quantum efficiency measurements show the enhancement to be due to the doping-induced shift in the graphene chemical potential that increases the graphene carrier density (decreasing the cell series resistance) and increases the cell's built-in potential (increasing the open circuit voltage) both of which improve the solar cell fill factor.

  • Chemical doping the graphene with bis(trifluoromethanesulfonyl)amide (TFSA)
  • doping reduces Graphene's sheet resistance and then Rs is reduced and in result built in potential increased so more efficiently e-h generated pares are separated

Molybdenum disulphide/titanium dioxide nanocomposite-poly 3-hexylthiophene bulk heterojunction solar cell [10][edit | edit source]

Abstract:

Hybrid bulk heterojunction (BHJ) PV using MoS2/TiO2 nanocomposite (~15um) and poly 3-hexylthiophene (P3HT) active layers is studied in this paper. MoS2 shows direct bandgap (1.85 eV) and indirect in multi layer (1.2 eV)

  • bulk MoS2 grinded and solved in acetonitrile and sonicated to produce ultrathin nanoflakes, TiO2 nanoparticles and MoS2 mixed in 2:1 ratio and deposited on ITO coated glass. Then front contact formation and annealing was performed at 450 C for 30 min. 1 wt% of P3HT in chlorobenzene was spin coated onto MoS2/TiO2 composite film. The P3HT diffuse into porous TiO2 network and form a BHJ. Back contact was performed by 50 nm Gold deposition (e-beam).
  • surface SEM image shows highly porous and randomly textured surface
  • Raman spectrum obtained. peaks confirm TiO2 and MoS2 materials
  • Energy band diagram of TiO2/MoS2/P3HT is shown, claimed P3HT is mainly used for charge separation by forming BHJ with large surface porous TiO2/MoS2 nanocomposite
  • I-V curve of device under dark and illumination is shown also semi log plot of the dark I-V curve is shown
  • External Quantum efficiency (EQE) in the range of 350-800 nm measured, showing maximum value of %61 at 485 nm.

Photonic design principles for ultrahigh-efficiency photovoltaics [11][edit | edit source]

Abstract: This paper focus on some new approaches of light management to minimize thermodynamic losses and reach to ultrahigh efficiencies. Entropic loss result in a systematic reduction of 400-500 mV in Voc for all practical solar-cell materials which indicate rooms for efficiency improvement. they trying to reach above %40 efficiency for a single junction solar cell by light management which was only possible previously with a triple junction solar cells.

  • Some approaches in light management are; 3 dimensional parabolic light reflectors, planar metamaterials, Mie-scattering surface nanostructure, metal-dielectric-metal or semiconductor-dielectric-semiconductor waveguide
  • multi-junction solar cell instead of single junction to minimize carrier thermalization and absorb most energy from solar spectrum
  • Series multi-junction structure has couple of disadvantages; fabrication complexity, current matching among the subcells is required (subcell generating the lowest current limits the overall multi-junction cell current), lattice match for different layer is also required
  • Alternating approach will by multi-junction in parallel array with spectrum-splitting photonic structure. In this approach a light splitting layer will filter the solar spectrum to that particular wavelength (bandgap) that underneath device is designed for.
  • In conclusion, using photonics structures for light managing inside the solar cells has a lot to improve the efficiency and not that much left in material science part of solar cells

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides [12][edit | edit source]

Abstract: This paper review applications of Transition metal dichalcogenides (TMDCs) in different devices such as transistors, photodetectors and PV devices. TMDCs materials have indirect Bandgap in bulk and multilayer structure however they go to direct Bandgap in single layer and sometimes in few layers structure. The bandgap of TMDCs are also sizabale around 1-2 eV by engineering the substrate or doping. TMDCs have MX2 structure and depending on the choose of elements can be semiconducting or metallic Electrical behavior. Generally MoX2 and WX2 shows semiconducting behavior and NbX2 and TaX2 are more metallic. The advantages of using TMDCs in PV devices are: the work functions of TMDCs and edges are compatible with commonly used electrodes. next advantage is to engineering the bandgap of each layer and build a heterojunction solar cell structure to harvest maximum energy from light. This structure potentially can be used to adsorb from visible to nearIR range.

  • Introducing TMDCs materials as 2D material
  • Discussing the physics of TMDCs (Band structure, Band gab, mobility etc.)
  • various approach for synthesis of TMDCs (Top down methods, and Bottom-up methods)
  • Applications such as PV, Photodetectors, LEDs, molecular sensors, flexible and transparent briefly discussed

High Efficiency Graphene Solar Cells by Chemical Doping [13] [edit | edit source]

Abstract:

  • Deposit Graphene Sheets (GS) on n-Si wafer with average PCE 1.5%
  • multilayer graphene to reach higher mobility
  • GS form a Schottky junction with n-Si
  • GS work also as ARC with reducing reflection 70% visible and 80% near IR
  • efficiency drops with thicker film, more recombination occurs
  • there is a trade off between conductivity and transparency

Graphene-based Schottky junction solar cells [14][edit | edit source]

Abstract: The Schottky junction, with merits of material universality, low cost and easy fabrication, is an alternative structure for solar cells. Compared to traditional indium-tin-oxide (ITO) based Schottky junction solar cells, graphene-based ones have merits of low cost, performance stability, and are applicable to flexible devices. In this highlight, we survey the recent research on graphene-based Schottky junction solar cells, including graphene-on-silicon Schottky junction solar cells and graphene/single NW (NB) Schottky junction solar cells. The working principle of them is discussed. These works demonstrate that graphene-based Schottky junction structures are promising candidates for developing diverse novel high-efficient and low-cost photovoltaic devices. The perspective and challenge of them are also discussed and anticipated.

  • Not new information, doesn't worth to read, small review of previous work on Graphene-based Schottky junction PV

Colloidal Antireflection Coating Improves Graphene–Silicon Solar Cells [15][edit | edit source]

Abstract: Carbon nanotube-Si and graphene-Si solar cells have attracted much interest recently owing to their potential in simplifying manufacturing process and lowering cost compared to Si cells. Until now, the power conversion efficiency of graphene-Si cells remains under 10% and well below that of the nanotube-Si counterpart. Here, we involved a colloidal antireflection coating onto a monolayer graphene-Si solar cell and enhanced the cell efficiency to 14.5% under standard illumination (air mass 1.5, 100 mW/cm2) with a stable antireflection effect over long time. The antireflection treatment was realized by a simple spin-coating process, which significantly increased the short-circuit current density and the incident photon-to-electron conversion efficiency to about 90% across the visible range. Our results demonstrate a great promise in developing high-efficiency graphene-Si solar cells in parallel to the more extensively studied carbon nanotube-Si structures.

  • they add TiO2 (nanoparticles 3-5 nm) ARC by spin-coating
  • there are some cracks on surface make it possible for acid treatment
  • without encapsulation after 20 days it degraded and PCE dropped from 14.1% to 6.5% because the loss of HNO3 doping effect
  • HNO3 vapor re-treatment recovered PCE to 14.5%

Graphene/semiconductor heterojunction solar cells with modulated antireflection and graphene work function [16][edit | edit source]

Abstract: In this paper, a theoretical model is presented to simulate the performance of graphene/semiconductor heterojunction solar cells. Using parameters extracted from experiments, our simulation gives consistent results with tested performance. two practical optimization treatments have been proposed.

  • First, the work function (WF) and layer number of graphene should be carefully adjusted. by applying an electric field or chemical doping and number of graphene layers
  • Second, antirefection (AR) layers should be introduced to mitigate the energy dissipation from the optical refection. polish Si reflect 35% of visible. Pillar array introduced to reduce reflection to 0.01%
  • To verify the simulation result, To verify the simulation result, solar cells based on acid modified graphene films and/or silicon pillar arrays were assembled, tested, and were found to deliver improved efficiencies of up to 7.7%
  • Table I and Table II in page 113 summarize simulation parameters and experimental test results respectively

High-efficiency graphene/Si nanoarray Schottky junction solar cells via surface modification and graphene doping [17][edit | edit source]

Abstract: In this work, we conducted a comprehensive study on high-efficiency graphene/Si nanoarray Schottky junction solar cells. Besides the Si nanowire (SiNW) array, a Si nanohole (SiNH) array was first used for the device construction since it showed the advantages in terms of larger effective junction area while enhanced light absorption is retained. It was found that surface charge recombination as well as graphene conductivity and work function played important roles in determining the solar cell performance. By suppressing the surface recombination with appropriate surface passivation, together with the careful control of the graphene layer number and the doping level, we found that the device performance can be significantly improved. Eventually, by inserting a thin conducting polymer poly(3-hexylthiophene) (P3HT) as the electron blocking layer between Si nanoarrays and graphene films, maximum power conversion efficiencies (PCEs) of 8.71% and 10.30% were demonstrated for the devices based on SiNW and SiNH arrays, respectively, as a result of reduced carrier recombination in the anode. The PCEs demonstrated in this work are the highest values achieved thus far for the graphene/Si nanoarray solar cells. The present results suggest great potential of the graphene/Si nanoarrays as high-efficiency and low-cost photovoltaic devices.

  • SiNH showed some superior result over SiNWs
  • Passivation/modification on the Si nanoarrays, together with the careful control of the graphene layer number and the doping time, maximum PCE values of 8.71% and 10.30% were achieved for the SiNW array and SiNH array based photovoltaic devices, respectively.
  • Table 1 in page 6598 summarize studied devices and Table 2 in page 6599 summarize degradation
  • The devices also exhibited excellent stability in air and remained stable after one week's storage in air.

Performance Enhancement of a Graphene-Zinc Phosphide Solar Cell Using the Electric Field-Effect [18][edit | edit source]

Abstract: The optical transparency and high electron mobility of graphene make it an attractive material for photovoltaics. We present a field-effect solar cell using graphene to form a tunable junction barrier with an Earth-abundant and low cost zinc phosphide (Zn3P2) thin-film light absorber. Adding a semitransparent top electrostatic gate allows for tuning of the graphene Fermi level and hence the energy barrier at the graphene-Zn3P2 junction, going from an ohmic contact at negative gate voltages to a rectifying barrier at positive gate voltages. We perform current and capacitance measurements at different gate voltages in order to demonstrate the control of the energy barrier and depletion width in the zinc phosphide. Our photovoltaic measurements show that the efficiency conversion is increased 2-fold when we increase the gate voltage and the junction barrier to maximize the photovoltaic response. At an optimal gate voltage of +2 V, we obtain an open-circuit voltage of Voc = 0.53 V and an efficiency of 1.9% under AM 1.5 1-sun solar illumination. This work demonstrates that the field effect can be used to modulate and optimize the response of photovoltaic devices incorporating graphene.

  • in terms of Graphene PV, this is not efficient as previous work but is new field effect solar cell is optimized by gate voltage
  • graphene doping, gate dielectric could be tested

Monolayer MoS2 Heterojunction Solar Cells [19][edit | edit source]

Abstract: We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photogenerated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%, which is the highest efficiency among all monolayer transition-metal dichalcogenide-based solar cells. The demonstrated results of monolayer MoS2/Si-based solar cells hold the promise for integration of 2D materials with commercially available Si-based electronics in highly efficient devices.

  • they did no passivation/ modification on Si surface before MoS2 transfer!
  • 15nm Al deposited on top of MoS2 ans charge collector (semi transparent) and 100 nm Al as electrode as top conact
  1. Novoselov, Kostya S., Andre K. Geim, Sergei V. Morozov, D. A. Jiang, Y_ Zhang, Sergey V. Dubonos, Irina V. Grigorieva, and Alexandr A. Firsov. "Electric field effect in atomically thin carbon films." science 306, no. 5696 (2004): 666-669.
  2. Fiori, Gianluca, Francesco Bonaccorso, Giuseppe Iannaccone, Tomás Palacios, Daniel Neumaier, Alan Seabaugh, Sanjay K. Banerjee, and Luigi Colombo. "Electronics based on two-dimensional materials." Nature nanotechnology 9, no. 10 (2014): 768.
  3. Beal, A. R., H. P. Hughes, and W. Y. Liang. "The reflectivity spectra of some group VA transition metal dichalcogenides." Journal of physics C: solid state physics 8, no. 24 (1975): 4236.
  4. Chandra, S., D. P. Singh, P. C. Srivastava, and S. N. Sahu. "Electrodeposited semiconducting molybdenum selenide films. II. Optical, electrical, electrochemical and photoelectrochemical solar cell studies." Journal of Physics D: Applied Physics 17, no. 10 (1984): 2125.
  5. Gourmelon, E., O. Lignier, H. Hadouda, G. Couturier, J. C. Bernede, J. Tedd, J. Pouzet, and J. Salardenne. "MS2 (M= W, Mo) photosensitive thin films for solar cells." Solar energy materials and solar cells 46, no. 2 (1997): 115-121.
  6. Li, Xinming, Hongwei Zhu, Kunlin Wang, Anyuan Cao, Jinquan Wei, Chunyan Li, Yi Jia, Zhen Li, Xiao Li, and Dehai Wu. "Graphene‐on‐silicon Schottky junction solar cells." Advanced materials 22, no. 25 (2010): 2743-2748.
  7. Xie, Chao, Peng Lv, Biao Nie, Jiansheng Jie, Xiwei Zhang, Zhi Wang, Peng Jiang et al. "Monolayer graphene film/silicon nanowire array Schottky junction solar cells." Applied Physics Letters 99, no. 13 (2011): 133113.
  8. Feng, Tingting, Dan Xie, Yuxuan Lin, Yongyuan Zang, Tianling Ren, Rui Song, Haiming Zhao et al. "Graphene based Schottky junction solar cells on patterned silicon-pillar-array substrate." Applied physics letters 99, no. 23 (2011): 233505.
  9. Miao, Xiaochang, Sefaattin Tongay, Maureen K. Petterson, Kara Berke, Andrew G. Rinzler, Bill R. Appleton, and Arthur F. Hebard. "High efficiency graphene solar cells by chemical doping." Nano letters 12, no. 6 (2012): 2745-2750.
  10. Shanmugam, Mariyappan, Tanesh Bansal, Chris A. Durcan, and Bin Yu. "Molybdenum disulphide/titanium dioxide nanocomposite-poly 3-hexylthiophene bulk heterojunction solar cell." Applied Physics Letters 100, no. 15 (2012): 153901.
  11. Polman, Albert, and Harry A. Atwater. "Photonic design principles for ultrahigh-efficiency photovoltaics." Nature materials 11, no. 3 (2012): 174.
  12. Wang, Qing Hua, Kourosh Kalantar-Zadeh, Andras Kis, Jonathan N. Coleman, and Michael S. Strano. "Electronics and optoelectronics of two-dimensional transition metal dichalcogenides." Nature nanotechnology 7, no. 11 (2012): 699.
  13. Miao, Xiaochang, Sefaattin Tongay, Maureen K. Petterson, Kara Berke, Andrew G. Rinzler, Bill R. Appleton, and Arthur F. Hebard. "High efficiency graphene solar cells by chemical doping." Nano letters 12, no. 6 (2012): 2745-2750.
  14. Ye, Yu, and Lun Dai. "Graphene-based Schottky junction solar cells." Journal of Materials Chemistry 22, no. 46 (2012): 24224-24229.
  15. Shi, Enzheng, Hongbian Li, Long Yang, Luhui Zhang, Zhen Li, Peixu Li, Yuanyuan Shang et al. "Colloidal antireflection coating improves graphene–silicon solar cells." Nano letters 13, no. 4 (2013): 1776-1781.
  16. Lin, Yuxuan, Xinming Li, Dan Xie, Tingting Feng, Yu Chen, Rui Song, He Tian et al. "Graphene/semiconductor heterojunction solar cells with modulated antireflection and graphene work function." Energy & Environmental Science 6, no. 1 (2013): 108-115.
  17. Zhang, Xiaozhen, Chao Xie, Jiansheng Jie, Xiwei Zhang, Yiming Wu, and Wenjun Zhang. "High-efficiency graphene/Si nanoarray Schottky junction solar cells via surface modification and graphene doping." Journal of Materials Chemistry A 1, no. 22 (2013): 6593-6601.
  18. Vazquez-Mena, Oscar, Jeffrey P. Bosco, O. Ergen, Haider I. Rasool, Aidin Fathalizadeh, Mahmut Tosun, Michael Crommie, Ali Javey, Harry A. Atwater, and Alex Zettl. "Performance enhancement of a graphene-zinc phosphide solar cell using the electric field-effect." Nano letters 14, no. 8 (2014): 4280-4285.
  19. Tsai, Meng-Lin, Sheng-Han Su, Jan-Kai Chang, Dung-Sheng Tsai, Chang-Hsiao Chen, Chih-I. Wu, Lain-Jong Li, Lih-Juann Chen, and Jr-Hau He. "Monolayer MoS2 heterojunction solar cells." ACS nano 8, no. 8 (2014): 8317-8322.