# Solar Cells

How i can calculate Strain from XRD data
How i can calculate Strain, i know that strain =delta d/ d, d= a/ sqrt(h^2+k^2+l^2) and d= lambda /(2*sin theta) but i don't get true answer if i use this equations.
mm Alsaud · King Saud University
Thank you for all. i want firstly find d value from d= lambda /(2*sin theta) But my problem is when i apply this formula on my results i get wrong answer. now how i can find d value like this example.
Do you think solar cells will be one of the main energy sources in the next few years?
I think that solar energy now has a good enhancement and solar cells have almost reached 40% efficiency. http://www.forcedgreen.com/2012/11/new-solar-cell-design-could-reach-40-efficiency/ This is safe, clean, durable and almost free after installation. Do you agree?
Yes, it will be. In Canada, majority of population lives in the house. I calculated that for two senior people living in two bedroom bungalow with garage and both roofs covered with solar cells entirely, their energy needs are 100 percent covered. With better battery, better cell efficiency and small quite windmill will definitely will add extra power. I came to conclusion that it is do-able. The greatest benefactors are countries in Africa, South America, Middle East and India where solar source is plentiful. We just need more time to make it better, cheaper and more realistic. Of course, our attitude is a big factor too.
How and why does the recombination rate behave ?
I have prepard the semiconducting material for solar cell applications, and i need to calculate the recombination rate? And itf life time of solar cells devices?
Abdelhalim Zekry · Ain Shams University
Dear Sadhanandam, Your question is a basic one concerning the variation of the recombination rate U from the bulk to the electrodes.In principle the recombination rate depends on the excess minority carrier density, say delta n, and the minority carrier lifetime ,Tau and specifically it is expressed by U = delta n/ Tau. The lifetime Tau is a material parameter and can vary from point to point in the material depending on density of the recombination centers in that point. Deep laying impurities and crystallographic defects may act as effective recombination centers. A homogeneous semiconductor material has constant density of recombination centers in the bulk and therefore constant minority carrier lifetime. HOWEVER, at the surface and at interfaces with metallic electrodes, there are normally high density of recombination centers because the interruption of the malarial and the presence many unsaturated dangling bonds.e You can measure the minority carrier lifetime of a semiconductor by the photconductive decay method. Concerning the excess minority carrier profile, it is controlled by the injection, diffusion, and recombination of the minority carriers. It is determined by solving the semiconductor equations in the regions of interest in the device with the proper boundary conditions. It is always so that the minority carrier excess will be largest at the injection boundary and zero or very small at the metallic contact. The zero at the metallic contact is the consequence of the assumed infinite recombination rate at the metallic electrode as explained previously. When the recombination rate is infinite, the excess must tend to zero. The surface recombination rate can be controlled by passivating the surface of the semiconductor. Also, the minority carrier in the bulk can be controlled by adding or removing deep lying impurities and or crystallographic defects. Knowing delta n and Tau one can determine the recombination rate profile. For more detail refer to the link https://www.researchgate.net/publication/236003006_Electronic_Devices?ev=prf_pub and the link: https://www.researchgate.net/publication/236002879_A_course_on_photo-voltaic_array_systems?ev=prf_pub wish you success.
Is there a method to measure the minority carrier lifetime of triple junction (ATJ) solar cells?
I want to find out the minority carrier lifetime in each layer of InGaP/GaInAs/Ge ATJ solar cells. What are the possible methods to measure lifetime in solar cells?
Thank you sir, As we don't have tuneable source separately, I will do full SR measurement using Bentham SR measurement system and will try to find out methods in literature..
• Saurav Kumar asked a question:
Why is pentacene a very promising solar cell material?
What are the major attributes which makes it distinctive from other material of the same group i.e. organic polymer?
Will the efficiency of a solar cell change with input illumination?
I measured the efficiency of an InAs/GaAs quantum dot solar cell under different input power from 0.5 to 4 sun in steps of 0.5. I found they do not change much. Efficiency under 0.5 sun was 11.3% and under 4.0 sun it was 11.6%. I heard from other researchers that this is not possible and that my results are wrong.
Keith Emery · National Renewable Energy Laboratory
For all PV devices the efficiency goes up with increasing light level until series resistance losses forces it to go down. In the region where it is going up the current versus voltage characteristics are dominated by the diode properties. At very low light levels the dark current or the current from the parallel shunt resistance dominates the fill factor. The flat region in the efficiency versus concentration is where the fill factor is decreasing with increasing light because it is limited by series resistance and the voltage is still increasing logarithmically with light. For concentrator cells this peak is near the design point such as 500 suns concentration for 1-sun devices this point is near 1-sun. The only difference between 1-sun cells and concentrator cells for some technologies is the series resistance losses in the metallization. As pointed out previously when you change the light level you must be careful not to change the spectrum or spatial nonuniformity or you will have an additional error as a function of light level. If the temperature is not well controlled changing the light level may also change temperature gradient between the temperature controlled plate and the cell junction.
What kind of parameters can we obtain using impedance spectra to get idea about TiO2 conduction band shift in DSSCs?
I want to get idea about effect of conduction band edge movement on Voc (open-circuit voltage). I have impedance spectra.
Qinghai Shi · Technische Universität Chemnitz
it depends on the geometry of your TiO2 and DUT. Generally you can get the conductivity from the real part of the impedance spectra. At first the equivalent circuit should be developed or cited from the finished work. Then you can abstract the conductiviy from the equivalent circuit.
How can you improve the adhesion of films deposited by the electrodeposition technique?
Specifically, I am working on the electrodeposition of semiconductors (CIGS films). At times, I end up getting poor adhesion between the thin-film and substrate. Use of complexing agents has been previously reported to improve adhesion. However, I want to avoid the use of complexing agents. Can somebody suggest a way to achieve good adhesion?
Tobias Deutschmann · Technische Universität Kaiserslautern
Hello, It would be much easier to give you a precice answer if, you would share the information of what substarte and what semiconductormaterial you are using. But in general, a thin (5-10 nm) layer of Ti or Cr will increase the adhesion of most layers. As long as those materials are not interakting with you semiconductor i would just try those.
Why does the performance of colloidal QD solar cells or LEDs degrade with successive IV measurements?
The performance of colloidal QD solar cells or LEDs degrade with successive IV measurements. Specifically, the resistance of the device drops to few kOhms.
Deniz Bozyigit · ETH Zurich
@Ramesh: I also see the temperature increase (by ~5-10K) under forward bias, which I guess is not avoidable with 2V*1A/cm^2 = 20kW/m^2. The vacuum we use is between 1e-4 to 1e-6mbar, depending on the experiment. 1e-4 is usually fine for our experiments.
How is the hole transported through the metal in an application to a solar cell?
If we sandwich a semiconducting material between two metal electrodes, on shining light, electron jumps from valence band to conduction band generating electron - hole pair in the semiconductor. Electron in conduction band of semiconductor can be transferred to the metal (provided work function of the metal is more than the conduction band edge of semiconductor) and the hole can be transported to other opposite electrode via hole transport medium. Some kind of solar cells like PbS based QD solar cells or other possible cases, the holes are transported to metal electrode without hole transport medium. I request can somebody explain how a hole can pass through the metal- if it is not, can you explain how to understand the hole transport through the different medium (I can imagine electron motion easily rather than hole) in solar cells and the necessary condition for the band alignment, starting from photo electrode material to counter electrode in DSSC or QDSC)?
Sateesh Prathapani · Indian Institute of Technology Bombay
Thank you very much Sebastian Wilken, your explanation is quite useful to me.
For CZTS, why are people still interested in the Stannite structure?
Historically the stannite structure was used first to analyze the experiment and Kesterite was initially found from simulations and later found in experiment. The kesterite-based CZTS has lower energy than stannite with a little energy difference, such that it is not supervising they co-existed with each other. The question is, why people still interested in the Stannite structure?
Léo Choubrac · University of Nantes
Many authors reports that the main problem with czts is the low Voc comparatively to the bandgap. It seems that this Voc loss is due to some bandgap/potential fluctuations. Because the bandgap of the stannite(ST) phase was calculated lower than those of kesterite(KS), a mix of KS and ST will induce some bandgap fluctuations. And because Cu and Zn are tricky to distinguish, it's hard to rebutt this hypothesis. Then many papers propose that these fluctuations are not the consequence of a KS-ST mix, but, at least in part, of the disorder on the copper-zinc layer (associated to the low energy-formation [CuZn2d + ZnCu2c] antisite defect).
• Navnita Kumari asked a question:
Which process is suiatable for synthesis for CZTS (Cu2ZnSnS4) nanorods?
Formation of CZT(S,Se)4 nanorods for solar cell application.
Can I use comsol multiphysics to model a ZnO/CuO solar cell?
I want to study ZnO as a semiconductor for solar cell type material. I need to compare its properites with the sillicon, so I started with comsol multiphysics. Is it a right choice? If not, what else?
Nabeeh Kandalaft · University of Sherbrooke MiQro Innovation Collaborative Center (C2MI) / Teledyne DALSA
Yes you can
Can renewables supplement or replace backup power systems in critical industries?
Critical industries such as hospitals and data centers are prone to power surges and losses. In the wake of such loses can they afford the costs in the loss of profits, life, and services to business and the community? Recruiting all interested parties to partake in a research journey into the sustainability of power backup systems for critical industries.
Frederick Carle · University of Ottawa
I don't know if at this stage I would say that renewables can replace replace backup power system but they can certainly supplement them. Especially if you consider solar combined with storage systems. A few potentially good storage technologies such as Ambri Inc. are coming to market this year. I hope they prove to be as good as they claim. One way solar can be a much better investment than currently use diesel backup generators is that when they aren't used for emergency situations, they can contribute to lowering the electricity bill of hospitals. In the long run, the system will most likely pay for itself.
How to deposit ZnO nanorods about 30-50 nm length?
Solar cell applications
Sebastian Wilken · Carl von Ossietzky Universität Oldenburg
In a hydrothermal synthesis from zinc acetate dihydrate in basic conditions, ZnO nanorods can be formed by oriented attachment of preformed quasi-spherical particles using certain precursor concentrations. Details can be found in Pacholski et al., Angew. Chem. Int. Ed. 41 (2002) 1188-1191
How can we apply solar load in Fluent CFD software?
For the purpose of solar collectors.
Tipu Sultan · Hanyang University
Thanks Basil Ali for the information.
Can someone explain the relation between flow rate and partial pressure of the gas?
Whether 1sccm=1.69x10-2Pa is it standard value? or it’s differ for chamber dimension and gas. In my case this equation not hold good. Usually I find partial pressure by the difference of final (working) to initial (base) pressure in the chamber. Whether we can correlate this flow rate and partial pressure by any other equation?
Michael Anisimov · Russian Academy of Sciences
Please send a Set-Up cheme, then you have chance to get a reasonable answer. My address: anisimovmp@mail.ru
What do you know about Perovskite (CH3NH3)PbI3 for the solar cell, 15%?
It seems to be a very promising material for solar cell, better than DSSC and OPV.
Xiangxin Liu · Chinese Academy of Sciences
@Chong Chen, could you please elaborate on the condition of your stability test? Did you do damp heat test?
Can anybody suggest some references in computing output power of photo-voltaic cells?Are they able to produce 50 KW or 100 KW power?
I want to model predict output power from pv cells.
G. Bothun · University of Oregon
Agree with Mike Valliant the power per "PV module" is not relevant as long as you can make an array of these devices - in this way it becomes fully scalable to your desired power output and there are plenty of interface electronics if you want specific voltages or currents.
Is it possible to achieve negative Voc and positive Isc in ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell?
In my experiments, the fabricated solar cell with mentioned structure shows negative Voc and positive Isc.
Minas Stylianakis · Technological Educational Institute of Crete
Which is the absolute value of the Voc you measure?
How does silane flow rate depend on the thickness of the sample?
I have deposited a-Si:H films by PECVD, as increasing the silane flow rate (SFR) & process pressure(PP), the thickness of sample decreases upto certain SFR& PP, again thickness increased as increased SFR&PP. Can anyone explain to me why thickness again increased? ( I kept remaining parameters constant)
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?
Baohua Jia · Swinburne University of Technology
Does anyone know any theoretical work on predicating the efficiency limit of perovskite solar cell?
Does graphene adhere to glass substrate?
Also, how do I use shadow masking in the spin coater? I need some gap in order to give contact between the two electrodes.
Youssef Jouane · Kochi University of Technology
You need surface treatment for your substrate, or use Hot-Spray Technique deposition
• Pramod K. Singh asked a question:
What is R Pervoskite? How is it useful in solar cells?
At present Pervoskite based solar cell seems novel alternative of DSSC.
What is the origin of equilibrium carriers in organic solar cells?
Do you know any articles?
Hung Phan · University of California, Santa Barbara
I think the equilibrium mobile carriers (holes, electrons) are only originated from thermal (kT) excitation of electrons across the energy gap (HOMO vs. LUMO) or across the dopant levels and HOMO/LUMO. In Michael's argument, defects/impurities... can be considered as "dopants". Anyway, if you don't shine the light to a S/C, thermal energy is the only energy source for carrier generation.
How and why does the recombination rate behave differently in the bulk of the active region and near the electrodes for solar cell devices?
Does the charge carrier mobility play a major role in this recombination profiling? Please share any related articles addressing the subject. Thanks!
Abdelhalim Zekry · Ain Shams University
Dear SHAIK, Your question is a basic one concerning the variation of the recombination rate U from the bulk to the electrodes.In principle the recombination rate depends on the excess minority carrier density, say delta n, and the minority carrier lifetime ,Tau and specifically it is expressed by U = delta n/ Tau. The lifetime Tau is a material parameter and can vary from point to point in the material depending on density of the recombination centers in that point. Deep laying impurities and crystallographic defects may act as effective recombination centers. A homogeneous semiconductor material has constant density of recombination centers in the bulk and therefore constant minority carrier lifetime. HOWEVER, at the surface and at interfaces with metallic electrodes, there are normally high density of recombination centers because the interruption of the malarial and the presence many unsaturated dangling bonds. Concerning the excess minority carrier profile, it is controlled by the injection, diffusion, and recombination of the minority carriers. It is determined by solving the semiconductor equations in the regions of interest in the device with the proper boundary conditions. It is always so that the minority carrier excess will be largest at the injection boundary and zero or very small at the metallic contact. The zero at the metallic contact is the consequence of the assumed infinite recombination rate at the metallic electrode as explained previously. When the recombination rate is infinite, the excess must tend to zero. The surface recombination rate can be controlled by passivating the surface of the semiconductor. Also, the minority carrier in the bulk can be controlled by adding or removing deep lying impurities and or crystallographic defects. Knowing delta n and Tau one can determine the recombination rate profile. For more detail refer to the link www.researchgate.net/publication/236003006_Electronic_Devices?ev=prf_pub wish you success.
How do i find out the most electrolyte conductivity materials in bio materials?
Ongoing research on the concept of power storage materials in bio solar pv cells.
What are the latest concepts for bio solar cell and pv cell materials in terms of storage materials?
Thanks.