Dear Khursheed

Usually, from the better the window layer has wide band gap, in order to transmittance all electromagnetic spectrum in visible region, and if the window layer has less energy gap, then some of the electromagnetic spectrum will absorbed at this layer before it can pass from the window layer to reached to the absorber layer, this mean loss in arrived incident photons (which have energy greater than energy gap of absorber layer) to the absorber layer, which will cause low efficiency of your device. With best regards

Dear Bilal Taher,

Thank you very much.

I have one more question, Graphene/MnO2 have been used as counter electrode in dye sensitized solar cells, Can it be use in perovskite solar cells??

Dear Khursheed

I am very sorry, because i didnt work in this type of solar cell.

I hope somebody help you, with best regards

The band gap of 2.4 eV shows that it will absorb photons below 514 nm wavelengths. One can try to reduce this absorption by using a very thin layer. However another important parameter to take into consideration would be the energy level matching. Is MnO2 n-type of p-type? 

I would not consider MnO2 to be a good choice for interfacial layer. However it would be worthwhile to do initial testing if you can make a mesoporous layer out of it.

Dear Swaminathan Sir, What is the optimum optical band gap of materials which is used in HTM in Perovskite solar cells ?.. Optimum thickness also?

Dennish, It would be better if you start a new thread/question regarding this. To answer your question - it depends on what architecture that you work on. If you work on inverted architecture (ITO/HTM/Perovskite/ETL/Cathode) then PEDOT:PSS is the best HTM to start with. 30-50 nm would be optimal thickness. If you work on normal architecture (FTO/ETL/Perovskite/HTM/Anode) then doped Spiro-OMETAD is your best option. Thickness vary between 100 - 200 nm for HTM. 

Best,

Swami

In perovskite or organic solar cell architecture, the role of interfacial layer is to reduce or increase the work function of electrodes, to have better charge collection (injection for LEDs), in this scenario, use of Cs2CO3 on ITO have reduces its work function, whereas, MoO3 on ITO increases its WF. Moreover, thickness is also much importance as of their frontier energies. For using LiF few (0-1) nm on ITO reduces WF, at thickness more than 2 nm  have deteriorate the transport. For higher thickness of interfacial layer, we have to consider their frontier energy for transport, for example electron injection layer should have its LUMO in between ITO WF and organic LUMO. For positive bias, HOMO is considered. 

Yes, MnO2 has lower WF and it will enhance electron transport if you choose to use thickness less than 5 nm, (https://www.researchgate.net/publication/257628071_Highly_enhanced_electron_injection_in_organic_light-emitting_diodes_with_an_n-type_semiconducting_MnO2_layer)

or if higher thickness going to be used check whether MnO2 has conduction band edge is lie between ITO WF to perovskite' LUMO to observe better electron transport.

Article Highly enhanced electron injection in organic light-emitting...

Justin, just because a layer is used for electron injection does not imply that it can be used for electron extraction. That is why both these devices using different transport/injection layers.

Not all injection materials can be used for improved charge collection, but few materials can act as both, MoO3, NiO, PEDOT:PSS.  It also depends on device architecture. For MnO2, i don't have clue.

We have mehtrohm potentiostate/galvanostate that operate with Nova software. Can anyone tell me how to perform charge discharge experiment for supercapacitors and what parameters to be changed/set.

Thanks for all of you for your valuable answers on MnO2.

Guys with sme electrocatalysis or photocatalysis experties, can you please guide me about the following text...

Lower cation oxidation states generally have the effect of decreasing an oxide's work function. so can someone guide me whether Na ion insertion will decrease the work function of MnO2?