Hello Maya,

that's very complex question, which cannot be answered in one sentence.

One would say that the fill factor, open-circuit voltage and short-circuit current might be the parameters to look at. However, there are many more like saturation current, diode factor, shunt and series resistance or carrier lifetime, recombination velocity, etc...

Another criterion/parameter is the band gap, which is a trade-off between open-circuit voltage and short-circuit current. Nevertheless, you maybe want to have significantly different band gaps for tandem-cells. That's a question of design: single or multijunction cell, contact types. Then you can further distinguish between crystalline and polycristalline, organic/anorganic or a mix.

Another imporant property is the interface quality between your absorber, contact and other layers. And finally the desired/needed microstructure of each layer should be considered.

There is much more to think about such as doping, growth process, etc. You should have a look to books like:

• Solar Cell Materials - Developing Technologies (Wiley)

Hope that will help you a bit!

Hello Maya,

that's very complex question, which cannot be answered in one sentence.

One would say that the fill factor, open-circuit voltage and short-circuit current might be the parameters to look at. However, there are many more like saturation current, diode factor, shunt and series resistance or carrier lifetime, recombination velocity, etc...

Another criterion/parameter is the band gap, which is a trade-off between open-circuit voltage and short-circuit current. Nevertheless, you maybe want to have significantly different band gaps for tandem-cells. That's a question of design: single or multijunction cell, contact types. Then you can further distinguish between crystalline and polycristalline, organic/anorganic or a mix.

Another imporant property is the interface quality between your absorber, contact and other layers. And finally the desired/needed microstructure of each layer should be considered.

There is much more to think about such as doping, growth process, etc. You should have a look to books like:

• Solar Cell Materials - Developing Technologies (Wiley)

Hope that will help you a bit!

Article Materials for downconversion in solar cells: Perspectives an...

Article Review on the role of materials science in solar cells

Thank you Mr. Torsten...

What answer you provided, is quite satisfactory.. and detailed... but actually my intention here is to move backwards..

I mean.. what parameters you explained are decided... only once the device is in hand...I mean after manufacturing...

one step backward.. and I'll be at growth process as you said..

I am still one step back..

I mean "the SELECTION OF THE MATERIAL ITSELF"...

what basic fundamental properties should a material possess for such application..

like band gap, you said... then what range of it would provide satisfactory results..

besides this, effective masses, dielectric const or other optical or thermal properties (what ever)...

I've gone through the literature too... but not satisfied with the explanation at many places...

Moreover, how much weight does each property show in efficiency measurement or performance..

any mathematical expression???

@ João Lucas de Souza Silva :

Thank you very much for the links...

will go through and let you know...

Hello Maya,

let me add to the very good answer given by Torsten ... From the material point of view, silicon or any other material used today, an important parameter is the band-gap energy of the material used to manufacture the solar cell ... For instance, silicon with 1.1 eV bandgap energy can only respond to solar radiations with wavelengths having energy levels close to 1.1 eV (little bit more) and sufficient to generate the electron-hole pairs. Different materials have different bandgap energy levels, so they respond with different efficiencies to solar radiations having wavelengths ranging from Ultraviolet to Infrared. That's why today, efficient solar cells (efficiency more than 44%) are manufactured with multiple P-N junctions, with different materials. Each P-N junction deals and benefits from a part of the wide solar energy spectrum. As Torsten said ... this is a wide and very complex question, but I am sure you can find more information in the references provided by de Souza Silva - Good Luck!

Hello Mr. Ali.. and thank you very much for considering the question..

hmm.. band gap is okay..

besides band gap, other properties?? (there are many for sure) which affects the efficiency effectively??

And can any mathematical relation or overall idea regarding the quantitative result can be estimated???

Best Regards

Hi!

A few points (only for single-junction SCs):

Fundamental requirement is: 1.0eV < Eg < 1.6eV (otherwise it's not worth trying, unless you are after solar windows or similar stuff). Then the material needs a sufficient absorption coefficient, alpha, to absorb all the sunlight within the diffusion (drift) length L of the minority carriers. Material quality of the absorber has to be good to transport generated minority carriers to the separating (often pn-) junction. This means the material should exhibit a low density of structural/atomic defects (creating eg recombination or scattering centers). A high density of these defects reduces the lifetime tau (recombination) and/or mobility µ (scattering). This will lead to a low L, since L = (tau*D)^1/2, with diffusion coefficient D=µkT. Mobility further decreases with effective mass m* (µ~1/m*), which is a result of the el. band structure E(k) (ie a material property depending on lattice and atomic species). In order to achieve a high build in potential (upper limit for Voc) the doping should be as high as possible (without deteriorating the mobility by too many point defects!). You should further try to process the absorber with as few grains boundaries as possible, since they usually (?!?!) act as electronic transport barriers and/or recombination centers...

I would say these are the most important points (macroscopically speaking). When you want to create a (hetero-) junction to establish a separating field, other parameters like the work function (or el. affinity) and interface coherence become important, too.

So for the start I would check for the band gap and the absorption. If that is given, try to make the material as defect-free as possible...

Best,

Jan.

I am attaching few articles for your reference. Hope , these papers will help you to solve your problem.

I am attaching a file from MIT course website. It explains in details about all parameters related to photovoltaic devices.

Hii Jan!

thank you so much for considering my question.

Okay.. so the quantities you explained, if you find all these parameters in favorable range..then does the material guaranteed to be a photovoltaic or still there may be juss probabilities. or other factors..??

Actually, I'm stuck with one of the questions from the reviewer..

that's why...

Thank you Mr. Singh for your references too.. will go through.. hope would be helpful..

thanks (Regards)

Dear Maya.

If a material absorbs light (like black paint) and it exhibits a diffusion length (which depends on the mentioned material parameters) large enough to transport the generated carriers to a separating junction, you can use it to observe a photovoltaic effect. YES! The better the properties (Eg_best = 1.15-1.3eV, L>thickness, well passivated interfaces) the higher the efficiency will be! This has nothing to do with probability (okay, in quantum mechanics everything is just probabilities, but that's a different story).

Haha.. by probability I dint mean that quantum part.. :-) Anyway..

Okay thanks..

thanks so much.!!!

Regards..

Hi!

try to study the different optoelectronics properties of your materials, in the first step try to work in optimal conditions like stability and try to find the parameters who can affect the efficiency .... you should be sure that your materials can get maximal transmission, maximal absorption, and minimal reflexion...,

My best regards!

@ Mr Laidouci,

Hello! Thank you for adding your views...

I agree.. Can you comment anything on the optical band gap??

I mean its importance and the optimum value for the application. (if possible)

Regards

Hi!

All materials with a large bandgap better to use in light emitters devices, in another hand, materials with small bandgap used in photovoltaics ... you can also control the bandgap energy range by changing in the amounts, result get a large optical absorption , ...so our goal covering a wide solar spectrum...

For single-junction solar cells the optimal band gap is in a range of 1.0-1.5 eV considering the Shockley-Queisser-Limit. Finally, you have a trade off between maximum open-circuit voltage Voc and short-circuit current Jsc. In principal, the larger the band gap, the larger the maximum Voc and the smaller the band gap, the larger the Jsc. so, covering a wide spectrum of the solar spectrum is not all to consider.

Hi!

@Torsten Schwarz, I agree with you

Thank you Mr Laidouci...

Hello Mr Schwarz: thanks a lot!

its interesting... so I need to have some balance between the Voc and Jsc.. for maximum efficiency... right ?? (correct me please if required)

but how to know if we reached at that point without going through any experiment??? and further can you suggest me any method to get the optical band gap?? using dielectric or reflectance spectra etc. Actually Tauc plot as well as Kubelka-Munk theory.. I've gone through and getting different results from both!!! so a lil bit confused I am..

And last one.. "covering wide solar spectrum is not all to consider" please elaborate if possible...

Thanks

Hi!

@Maya Kaur,There are many computational programmes can be used to study and calculate different optoelectronics parameters by different methods using software such as " Wien2k, Materials Studio " based on Ab-initio calculations, experimentally with reflection or transmission spectra to get the value of Eg , we usually use the Tauc relation, which is given by this equation: αhν = A(hν - Eg )n , about the Jsc and Vco , if the area "I(V)" increase that means the efficiency increase too

we know that Efficiency = Vco*Jsc*FF/Pin;

Regards!

The appended papers may help you

https://www.researchgate.net/publication/283338024_Effect_of_Se_addition_on_optical_and_electrical_properties_of_chalcogenide_CdSSe_thin_films

https://www.researchgate.net/publication/281495242_Influence_of_composition_on_optical_and_dispersion_parameters_of_thermally_evaporated_non-crystalline_Cd50_S50-xSex_thin_films

Thank you very much Mr. Laidouci... Yes, exactly theoretical tools are available and they provide the reflectance spectra.. and by fitting the equation, you just mentioned, optical band gap is achieved (Tauc Plot)

and as I said, that I've done already. I've retrieved the value from Kubelka Munk function as well... but I'm getting different values from both the methods! and that's my issue!!!

So, basically my confusion is which method should be considered?? or if any other better method is available for the same??? Moreover what values I'm getting are corresponding to the peaks in Im(epsilon) curve.. I'm not sure if these are the same...

but i think it shouldn't be.. for if it were, then what would be the need of fitting!!?? no???

Regarding I-V curve, I agree with you.. but my question was " without going through any experiment" .. and these I-V characteristics are achieved experimentally if I'm not wrong!!

any theoretical approach??