Why additives are used in organic solar cells? Do they really participate in enhancing the performance? Don't they go off during drying or annealing? How their existence can be ensured after these process?
Hi Sivaraman,
if by additives you mean compounds such as di-iodo-octane (DIO) or chloronaphthalene (CN), which are added to the solution of your donor and acceptor, then the answer is that these additives - roughly speaking - enhance the morphology of the active layer/bulk heterojunction. Or at any rate they give you more control over the morphology by fine tuning the amount of additive. They work by altering the time it takes for your solvent to dry and therefore influence the way your BHJ-morphology will end up. A good starting point to learn more about additives would be the following review paper: Article Additives for morphology control in high-efficiency organic ...
Thus, the performance enhancement usually is linked to the improved morphology, and the additives indeed should evaporate during the deposition.
If, however, you are talking about ternary or even quaternary blends, then these mixtures of several donor(s) and/or acceptor(s) do remain as part of the BHJ in the active layer. Here the improvement can be due to better charge generation (i.e. more photons can be absorbed over a wider range of the spectrum) and/or better charge separation (advantageous energy levels for exciton splitting and/or charge transport). Morphology also plays a huge rule again. If you want to read up on this topic, this review paper might be a good start: https://pubs.rsc.org/en/content/articlelanding/2015/ee/c5ee02641e/unauth#!divAbstract
I hope I could help.
Hi Sivaraman,
if by additives you mean compounds such as di-iodo-octane (DIO) or chloronaphthalene (CN), which are added to the solution of your donor and acceptor, then the answer is that these additives - roughly speaking - enhance the morphology of the active layer/bulk heterojunction. Or at any rate they give you more control over the morphology by fine tuning the amount of additive. They work by altering the time it takes for your solvent to dry and therefore influence the way your BHJ-morphology will end up. A good starting point to learn more about additives would be the following review paper: Article Additives for morphology control in high-efficiency organic ...
Thus, the performance enhancement usually is linked to the improved morphology, and the additives indeed should evaporate during the deposition.
If, however, you are talking about ternary or even quaternary blends, then these mixtures of several donor(s) and/or acceptor(s) do remain as part of the BHJ in the active layer. Here the improvement can be due to better charge generation (i.e. more photons can be absorbed over a wider range of the spectrum) and/or better charge separation (advantageous energy levels for exciton splitting and/or charge transport). Morphology also plays a huge rule again. If you want to read up on this topic, this review paper might be a good start: https://pubs.rsc.org/en/content/articlelanding/2015/ee/c5ee02641e/unauth#!divAbstract
I hope I could help.
Hi Sivaraman,
You can see this paper
DOI: 10.1002/aenm.201401426
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