I prepared some ITO/ZnO/CdS/CZTS and ITO/ZnO/ZnS/CZTS samples but when I made IV measurements, these samples exhibited diode behavior (I =0 until arriving to around V=0,5 V where I increases quickly). The problem is that there was no difference between dark and light IV curves, so what are the possible reasons for this? thank you in advance
Dear Zeineb the I-V in dark was similar to the one under light mean that no carrier generated and no photovoltaïque effect furthermore may be there is small current (micro) you can't see it so you have to improve some experimental condition of the absorber and buffer layer.
best regards and good luck
Thank you dear Fatima. I know this. But I mean what would cause the absence of photovoltaic effect? Is it the existence of a lot of defects in the absorber layer so decreasing its thickness will lead to a decrease in the defects and perhaps increase the short circuit current. Or oppositely, I should increase the absorber layer thickness to get larger generation? Can it be due to the high roughness of ZnO layer, which causes a high roughness of the upper layers too, thus leads to higher recombination?
I found a sentence: "Significant power losses caused by the presence of a shunt resistance, RSH, are typically due to manufacturing defects, rather than poor solar cell design" what they mean by solar cell design? do they mean that thickness is not the main problem but the absorber itself for example?
Hello, Zineb
The following is the "Equivalent circuit including series and shunt resistances" of solar cells, maybe there exist certain circuit break or disconnection inside of your cells.
Honestly speaking, I met similar situations and found that's because the contact was not good, but mine was not CZTS thin-film soar cell but a QDSSC. Beyond that, in your case, that may well be the passivation of the light active layer CZTS by other layers or the transition region caused by mutual diffusion.
In addition, what 's your contact electrode of the CZTS side? The contact electrode is also important, and I guess the conduction type of your CZTS is P-type so that the curves exhibited diode behavior.
Another question I confused a little about your cell structure is: what's the role of the CdS or ZnO layer? I'm not very familiar with this type cells and I'll appreciate it if you can explain that properly.
Best wishes
I think the "solar cell design" means structure or construction of the cell, absorber and its properties determined by the manufacturing process are the main issue according your refered sentences.
Dear Zineb Benzait, another reason that this could happen is the high leakage current that your diode exhibit. Also, if your illuminated area is too small your photocurrent will be also small and maybe as it was recommended you should check your experimental setup (like the scale in the SMU). If you can provide some IVs it will be helpful.
@Zhiqiang Yu my contact electrode of the CZTS side is Ag. the conduction type of your CZTS is P-type as you estimated. CdS is a buffer layer whereas ZnO is the window layer. Here a video that can give you idea about SIGS and CZTS solar cells: https://www.youtube.com/watch?v=sX_HB4-a0Tg
@Stelios Kazazis the samples area is about 1 cm2. an example of IV curves is attached.
For experimental details, ZnO layers (around 500 nm) were first deposited into ITO glasses by pneumatic spray pyrolysis technique at 450 degree, followed by CdS or ZnS buffer layer (around 100 nm), then by CZTS (around 800 nm) that was deposited at 150 degree by spraying a CZTS ink (prepared previously by hot injection method). after finishing, the samples were heat treated at 250 degree for 40 min. then Ag contact points were made by silver thermal evaporation (around 200 nm). As you see there are a lot of parameters that can be changed but I have very few time. I started working in this project before almost two months and it remains only one month to finish it. So what do you advise me to do? Which parameters should I change first, or which layer should I improve? I think it is the absorber layer right? because it is the main part of the solar cells. Noting that ZnO layers are very well crystalline but they exhibit high roughness which may generat rough upper layers.
Noting also that these are inverted cells, for this reason CZTS layers were annealed at relatively low temperature (which is related to another question here https://www.researchgate.net/post/What_is_the_effect_of_CZTS_CdS_heterojunction_annealing_at_high_temperature )
Thank you in advance for your help, and best regards
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