Solar Cells

Solar Cells

  • Olívio Fernandes Galão added an answer:
    What is the most suitable electrolyte for a chlorophyll sensitized solar cell?

    A dye sensitized solar cell made with chlorophyll as a photo sensitizer, what will be the most optimal electrolyte to be used?

    Olívio Fernandes Galão · Universidade Estadual de Londrina

    polymer electrolyte (poly (epichlorohydrin-co-ethylene oxide) 84:16, Nal and I2

  • Alessio Bosio added an answer:
    How can I reduce the shunt of CIGS solar cell without add the i-ZnO buffer layer?

    Is it possible?

    Alessio Bosio · Università degli studi di Parma

    The main reason of the presence of shunt paths in the CIGS-based solar cell is the formation of foreign phases within the CIGS film. Typically these binary phases are Cu-rich and particularly unstable; they often release Cu atoms, which being a good diffuser segregates into grain boundaries, creating preferential paths for the channeling of the reverse current making the diode slightly rectifying. Particular care has to be used in order to obtain a uniform monophasic CIGS film.
    The preferential paths can similarly come from the diffusion of atoms of the III group present in the TCO (Al in the case of ZnO (Al) or In in the case of ITO). It is to prevent the diffusion of these atoms that a pure ZnO buffer layer is normally used. Instead of the i-ZnO film  an  undoped SnO2 layer can also be used.

  • Ben E Urban added an answer:
    How can I prepare stable ZnO nanoparticles for solar cells?

    I tried the method reported in that paper (DOI: 10.1038/NPHOTON.2013.342) and It worked very fine but I noticed that the end product is changing with time, over almost three weeks or less,  from a white suspension into a clear solution.

    I used the ZnO nano particles as soon as I prepared them and they worked but know I am not sure of the quality of the ZnO nano particles since they look different than before. 

    Is that normal? What can I do to stop this? Do I need to prepare fresh ZnO nano-particles every time I will need them? and if there is a more stable reliable method, please let me know.

    Ben E Urban · Northwestern University

    ZnO nanoparticles stability greatly depends on the method used to create them. It is almost impossible to create a clean surface in chemical methods (outside of arc vapor deposition). Next, in water or organic (CH, CH2, CH3) solutions, ZnO tends to get larger, probably through van der waals force. Surface charge, which is difficult to avoid, will also affect solution stability. Finally, size distribution affects size stability. Your question is very difficult to address. I have seen groups that coat the surface with hydrogels (chitosan, NIPAM) to create stable solutions. In actuality, their solutions condensate, but can be re-dispersed to the same size and concentration using sonication. My advice would be to either make a a large quantity and use surface coating (which will certainly affect optical properties) to make a stable solution OR make a large concentration in the powder form and disperse it in the desired concentration before your experiments.

  • Ajay Kumar Baranwal added an answer:
    ITO or FTO for perovskite?

    Hi,

    considering the efficiency of device Which conductive transparent material is better for perovskite thin film as a part of solar cell device, ITO or FTO? Thanks.

    Ajay Kumar Baranwal · Kyushu Institute of Technology

    Choice of FTO glass or ITO glass is preferable by its work function. Both have different temperature susceptability also. Lower work function TCO glass is generally prefarable but Indium is rare material and ITO glass is costly as compared to FTO glass.

  • Juan Pablo Morales Arias added an answer:
    How do you dissolve polyethyelene terephthalate (PET)?

    I'm trying to dissolve PET to make a film out of it. I'm having a hard time finding good solvents and procedures online and would appreciate any help I can get.

    Juan Pablo Morales Arias · University of Buenos Aires

    Dissolve PET it in Dichloromethane (DCM) and put in a magnetic mixer by a couple hours.

  • Dhirendra Kumar added an answer:
    How does the use of additives (e.g.ionic-liquid based electrolytes) enhance the stability of a dye-sensitized solar cell?

    Generally it was found that the use of additives in redox mediator [iodide/triiodide] cause not only improved performance but also increase device stability. In particular, I want to know the impact on the device stability. Can it affect the dye-desorption from TiO2 that has direct impact on the long-term stability of DSSCs?

    Dhirendra Kumar · National Taiwan University

    Thanks for your reply. I can understand the utility of non-volatile solvents to improve the device stability. But what about effect of additives. In general they improve photo-voltage but also they cause better durability. So, how they improve the device stability as most of the reports describe the results only by employing them in different concentrations. There is no clear concept regarding the same.

  • Tahmineh Mahmoudi added an answer:
    What is the main issue in CZTS Solar cell fabrication with precursor base thin layer?

    I've been fabricating CZTS thin films and NPs and all the properties, such as: band gap, carrier mobility, composition, XRD are good. But when I use them as sensitizer in CZTS SC, the devices don't respond to light illumination. The IV curves are linear, with negative slope.

    Tahmineh Mahmoudi · Chonbuk National University

    Thank you, yes I have checked it, there is tiny holes and cracks in thin film. 

    For electron acceptor I use AZO/i-ZnO.

  • Gilles Horowitz added an answer:
    Is it possible for quantum efficiency of a solar cell be more than 100% for a particular range of wavelength?

    In my simulation research work for nano structure based solar cells, for a particular wavelength range I have been getting quantum efficiency more than 100%, but till date not able to find out the reason behind the cause, that's why I need to know whether technically it is possible or not?

    Gilles Horowitz · French National Centre for Scientific Research

    In short: *Quantum* efficiency can be higher than 100%, but *power* efficiency must remain lower than what predicted by Carnot's principle. In other words: One photon can generate more than one electrons, but the total energy of these electons will be lower than that of the incident photon.

  • Narendra Bandaru added an answer:
    How thick is the buffer layer in solar cells?

    How to determine the optimum buffer layer thickness for a solar cells. Is there any specific range for the buffer layer thickness or special equations from which we can calculate the same.

    Narendra Bandaru · Indian Institute of Technology Gandhinagar

    If thickness increases or decreases, what is the physics involved in that..

    Which parameters are going to effect by varying the thickness.

  • Bindu Salim added an answer:
    Why a solar cell have a linear IV curve in light?

    I have fabricated a Solar cell which has diode like behavior in dark, but has linear I-V curve in 1 sun illumination. What could be the reason of this linear IV curve under light? 

    Bindu Salim · PSG Institute of Advanced Studies

    Thanks Sebastian

  • Khursheed Ahmad added an answer:
    Is any one used this complex [Ru(bPy)3Cl2]  as a sensitizer in dye sensitized solar cells?

    .

    Khursheed Ahmad · Chonbuk National University

    I think No, but you must review it before use

  • Laurent Artola added an answer:
    How can we ensure a unique electric field in the multilayer solar cell?

    A semiconductor can absorb photons with the energy of its band gap in a solar cell. Photons with lower energy than the band gap of the devices are not absorbed. Solar radiation contains a broad range of wavelengths. Solar cell actually achieves nearly 100 % conversion at particular wavelengths of light, because electron hole pair can be produced from a single photon at a particular wavelength. However, an electron hole pair is also produced when a photon with a shorter wavelength (higher energy) is absorbed, in which case the excess energy is wasted as heat. This is a cause of low efficiency of the silicon solar cells for its small optical band gap. In multi-junction solar cells, each junction (subcell) absorbs sunlight from a specific region of the spectrum. The subcells can be stacked on top of one another so that sunlight first strikes the highest band gap subcell, which is tuned to light with the shorter wavelengths (highest energies). The longer wavelengths pass through the first subcell and strike the lower band gap subcells (second one), and so on. This arrangement offers a significant advantage over single-junction solar cells. In this way the efficiency of the solar cell is been enhanced. But problem is making a unique electric field from upper electrode to bottom electrode for moving the excited carriers to the outer circuit. 

    Laurent Artola · The French Aeropace Lab ONERA

    You should be interesting in the late work from R. J. Walters et al, "Detailed Characterization of the Radiation Response of Multijunction Solar Cells"  presented at 2015 NSREC conference. This work presents the response of triple-junction solar cells to proton irradiation is analyzed using electroluminescence (EL). This analysis allows the dark current of each individual subcell to be determined providing insight into the radiation response mechanisms.

  • Thomas Walther added an answer:
    Can anybody suggest the optimal thickness of GaAs on Si to make an high efficient cell?

    I want to deposit GaAs on p-n junction Silicon solar cell. The deposition of GaAs is done by electron beam method, but after annealing at 400-700 oC, the structures are changing as seen from FESEM but there is no sign of GaAs from XRD measurement.

    Can anybody suggest me what to do?

    If any body wants , i can provide FESEM and XRD data.

    Thomas Walther · The University of Sheffield

    GaAs on Si for a solar cell will only make sense if you can keep the density of dislocations resulting from the lattice mismatch low. This will need high-quality epitaxy by MBE or CVD methods, not e-beam deposition or sputtering.

  • Atharva Sahasrabudhe added an answer:
    How can one measure current vs. time or voltage vs. time curves using a source-meter (keithley)?
    I need to measure voltage and current transients on my devices (solar cell, photodetector). Can this be done using a keithley sourcemeter? I have a 2602A series sourcemeter from Keithley (if that helps).
    Atharva Sahasrabudhe · Indian Institute of Science Education and Research Kolkata

    Nope...but i m now using a potentiostat to measure the same. It has a built-in finction to measure transient current or voltage

  • Hafiz Muhammad Yar added an answer:
    Can anyone offer advice on synthesising ZnO quantum dots for solar cells?

    1,Octadecylamine.........2..octadecene ...........I want to make ZnO Quantum Dots for Solar Cells, so i read the Article A study of photoluminescence properties and performance improvement of Cd-doped ZnO quantum dots prepared by the sol–gel method........in this article why they use 1,Octadecylamine.........2..octadecene for what purpose except of these compound what other i acn use? and washed rapidly means ? what method to wash Please if some one guide and help me in this regard.

    Hafiz Muhammad Yar · University of Ulsan

    Dear  Kwangyeol Lee

    Thank so much for your information i am following your procedure and let see what will happened at the end of the experiment,

  • Bill Williams added an answer:
    What is the most appropriate lamp type for handmade solar simulator?

    I need to get a light source that simulate the sunlight in order to test my samples. Can I use "400 W metal halide lamp" or " Halogen lamp" is better?

    Bill Williams · Birkbeck, University of London

    A raw metal halide (HMI) lamp will produce a spectrum that achieves ASTM/IEC Class B spectral match. A raw xenon will require some IR clipping filters to achieve a similar spectral match (see link attached). Metal halide lamps are also cheaper and have a better temporal stability than xenon without the need for feedback control.

  • Dalia Arafa added an answer:
    Can I use the three diode model to simulate the physical behavior of any pv module?

    Can i use the three diode model to simulate the physical behavior of any pv module? Edit
    can i use the three diode model to simulate the physical behavior of any pv module , or there are any restrictions on using this model . if there are any restrictions what are they? why?

    three diode model is valid to simulate the physical behavior of any pv module, or restricted on certain types of pv cell 

    Dalia Arafa · Fayoum University

     great answer

    i read the first paper you attach it , thanks alot prof for your benefit  response , i conclude this  note of using the three diode model when i read paper of 2007 for modeling multicrystalline solar cells, so i think why we don't apply three diode for different multicrystalline solar modules. 

    thanks 

  • Hammad Cheema added an answer:
    How to get good film forming properties for methylammonium lead bromide?

    I tried the solution processing method with 1:3 molar ratio of PbBr2:MABr respectively dissolved in DMF. But when I spin coated the solution on glass substrate, the film was not formed properly and unevenly. I tried several spin coating's speeds and for several times but it didn't improve significantly. Also, I got some orange films and yellow films. 

    Hammad Cheema · North Carolina State University

    In that case, one thing that might help is to treat your substrate with oxygen plasma for 10-15 mintues and then spin coat with the solution.

  • Dalia Arafa added an answer:
    Ask about if the three diode model is valid to present any pv device?

    i want to know if three diode model can present any pv module or restricted only for certain types of pv cell (cell only ).  and why? 

    Dalia Arafa · Fayoum University

    please dear  Trung-Kien Vu ·

    clarify what you want to say, if three diode mmodel is valid for pv module like pv cell or not and why ?

    thanks  

  • Svetlana Polivtseva added an answer:
    How can I synthesize CuInS2 by Chemical Solution Deposition Method ?

    Respected all,

    I synthesize P-type absorber layer of CuInS2 by spin coating method with following salts

    Copper Chloride, Indium Chloride, Thiourea Cu:In:S2  1.1 :1 : 4 with 2-methoxy ethanol or 2-propanol(IPA) as precursor solution. I synthesize CuInS2 on glass substrate with 10 layers at drying temp 300 C. and annealing temp 420 C in Nitrogen atmosphere.

    But, when i did xrd analsis there are several impurity peaks like CuS, In2O3 

    Please prove me some guideline or literature so I can synthesize CuInS2 without any sub-phases  by solution deposition or any other method.

    Regards 

    Jigar Chaudhari

    Svetlana Polivtseva · Tallinn University of Technology

    Dear Jigar, write your system what was used. Real molarity of the salts and deposition atmosphere (air or N2).  There are two main reasons 1. Uncomplexed thiourea decomposes itself . 2. Metal cations form several compleses  -where thiourea ligand and ligands of solvents are in competition. Probably, In (3+) is uncomplexed in conditions of your experiment. So, you have to increase the precursors molar ratio (Me-S) in your parent solution, decrease the drying temperature or change a solvent system used.

  • Robert Karsthof added an answer:
    Can I calculate the quasi Fermi levels in a p-n junction solar cell in the case of the absorption of a single photon?

    We know that the "driving force" that separates photo-generated charge carriers in a solar cell is not merely the built-in potential of the junction, but the gradient of the electrochemical potential which takes into account both electrostatic potential and concentration gradient of charge carriers.

    If we consider now the absorption of a single photon within the space charge region of a solar cell p-n junction, this locally creates a small increase of charge carrier concentrations and thereby also a splitting of the quasi Fermi energies (=electrochemical potentials, Fn,p) of electrons and holes. Is it possible to draw the quasi Fermi levels, for example under short-circuit conditions?

    My problem is that I do not understand how a separation of the e-h pair can happen when considering the electrochemical potentials. I am aware that, since the excitation takes place within the built-in electric field of the junction, the carriers will drift into their respective majority regions. But from the electrochemical point of view, there should only appear a "delta-like" peak in Fn and Fp, and since there is no gradient of the quasi Fermi levels, no directed current can result..

    Robert Karsthof · University of Leipzig

    I guess this would create locally different quasi-Fermi levels looking like peaks. The charge carriers would then be driven into the 'inactive' regions of the thin film by drift and diffusion. But what do you mean by 'photonic effects'?

  • Hairen Tan added an answer:
    Did the photon recycling effect exist in perovskite solar cells?

    Recently, I did some research work on predicting the efficiency limit of perovskite solar cells [Appl. Phys. Lett. 106, 221104 (2015) http://dx.doi.org/10.1063/1.4922150]. I also added some points in wikipedia [https://en.wikipedia.org/wiki/Perovskite_solar_cell#Physics].

    According to the detailed balance model by Shockley and Queisser, the maximal output power of a solar cell can be achieved if the following set of hypotheses are fulfilled:

    (1)     Carrier populations obey Maxwell-Boltzman statistics. Particularly, the quasi-Fermi levels of electrons and holes are uniformly split through the cell and the split equals the applied voltage. The assumption is reasonable if mobility of photocarriers (electrons and holes) are sufficiently large. Regarding perovskite materials, charge carrier mobility as high as 10 cm2 V-1 s-1 has been observed.

    (2)     Radiative band-to-band (bimolecular) recombination mechanism is the only one existing. Nonradiative recombination, such as Auger recombination, trap (defect) assisted recombination, etc, are ignorable. Different from silicon with an indirect bandgap, perovskite material has a direct band gap. Therefore, Auger recombination is sufficiently suppressed, which has been verified in recent experimental results. Moreover, light emission from perovskite solar cells is dominated by a sharp band-to-band transition that has a radiative efficiency much higher than that of organic solar cells.

    (3)     Internal conversion efficiency reaches 100%. When one photon is absorbed, it produces one electron-hole pair; and when one electron-hole pair recombines, it produces one photon. For perovskite solar cells, the internal quantum efficiency approaches 100%.

    (4)     Photon recycling effect cccurs in the cell. Although a photon will be created by one electron-hole pair recombination during the radiative recombination process, the photon can be reabsorbed at a different spatial location in the cell, which creates a new electron-hole pair. Designs of light trapping and angular restriction can improve the photon reabsorption process and thus maximize solar cell efficiency. For perovskite solar cells, the existing of photon recycling effect is still unclear.

    From my personal point of view, points 1—3 now are clear. The unclear point is point 4. We knew that photon recycling effect has been confirmed in GaAs solar cells recently. Did the effect exist in perovskite solar cells? How to confirm it? I’d like to listen to your opinions.

    Hairen Tan · Delft University of Technology

    Never forget that the light trapping structures may considerably generate higher defects density. In direct bandgap solar cells, all the state-of-the-art devices (including GaAs) are based on flat structure (no light trapping, only AR). As for polycrystalline solar cells, such as Perovskites, the SRH recombination dominates, thus photon-recycling is useless from a practical way. For very high-quality GaAs with extremely low defects density, it is true that photon-recycling can help to improve the efficiency, but only a bit.

  • Abdullah Ashraf added an answer:
    How can you do a sulfurization process safely?
    I going to make sulfurization of copper, indium thin layer. Is it ok to do it with a closed furnace by covering the glass substrate and sulfur power by beaker? 550-580 deg Celsius temperature will be used. Or I should do it at a tube furnace?
    Abdullah Ashraf · Qatar University

    yes

  • Ali Gharaee added an answer:
    What is the perovskite CH3NH3PbI3 refractive index value ?

    Since the first report on a long-term durable solid-state perovskite solar cell with a power conversion efficiency (PCE) of 9.7% in 2012, a PCE as high as 19.3% was demonstrated in 2014, and a certified PCE of 17.9% was shown in 2014. Such a high photovoltaic performance is attributed to optically high absorption characteristics and balanced charge transport properties with long diffusion lengths.

    I am studying now how to improve solar cell with provskite, we actually made many samples in MU labs at electrical engineering department, and start to simulate the results using FDTD, I try now to find for refractive index and extinction coefficient for CH3NH3PbI3 with respect to wavelength.

    Ali Gharaee · Khorasan Institute of Higher Education

    http://pubs.acs.org/doi/abs/10.1021/jz502471h

  • Nilotpal Bhattacharjee added an answer:
    Is it OK to recognize a solar cell by an absorber layer only?

    My paper (a review on indium sulfide buffered chalcopyrite and CdTe solar cells from various deposition techniques) was rejected by a reviewer saying solar cells are recognized by absorbers only and that buffer layer doesn't contribute toward improving the efficiency of a solar cell. I don't agree with this statement. Could anyone shed light on this please? Thank you.

    Nilotpal Bhattacharjee · Assam University

     The capacitance between the absorber  and buffer is significant. Any solar cell when acts as an energy source is depicted by the small curve in the forward biasing region in its I-V characteristics, which can be influenced by the buffer layer as mild disturbance by its electron transport can easily disturb the electrons in the  absorber. Moreover  the absorber is in nano scale or two dimensional than the significance of buffer gets more relevant.

  • Suhail Anjum Abdur Raheem Sayyed added an answer:
    How can I improve short circuit current in Dye Sensitized Solar Cells?

    The solar cells we are making are having good voltage arouen 350 to 500mV but current is low in microAmpere. How to improve current. we are using low cost dyes such as rose bengal and eosing y.

    Suhail Anjum Abdur Raheem Sayyed · Ahmednagar College

    dear sir I could not access the supplemental information. If you could send on my mail sasayyed81@gmail.com then I will be very much thankful to you.

  • Wei E. I. Sha added an answer:
    What's the major challenge of perovskite solar cells?
    It is such a hot topic these days. What's the major challenge in this field? Is it really going to be a mainstream technology?
    Wei E. I. Sha · The University of Hong Kong

    you can read my paper in http://dx.doi.org/10.1063/1.4922150. I also edit wikipedia for perovskite solar cell (physics part).

  • yu-chu Tseng asked a question:
    What is the mechanism of Al bead on the PERC cell ?

    according to our experiments, sometime a few beads happened on the cell 2 dges on the direction of cell conveyed in the co-firer, sometime beads happened on the 4 edges, and sometime we found beads happened on the ends of back contact lines no matter the direction of cell conveyed .  The bead size is very small. The Al film thickness  checked by SEM is not much different between cell center and edges.

  • Harsimran Singh Bindra added an answer:
    Why is the open-circuit voltage in a PV cell less than the bandgap voltage of the PV material?

    Why is the open-circuit voltage in a PV cell less than the bandgap voltage of the PV material?

    In other words, what is the physical interpretation of the voltage factor in a PV material? In which: VF = V_oc / (E_g/q).

    Any detailed physical explanation would be highly appreciated.

    Harsimran Singh Bindra · Amity University

    i am not able to calculate values of Voc for Si, Ge and GaAs as per the formula, please help me out with this problem

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