Hi, I've been reading PF threads for a long time but never really had a question to ask.. until recently.
I am doing some of my own studies on OPV devices (i'm still a high school student, so I have no prior research experience of in-depth knowledge on processes that take place at the atomic level during the operation of the device). i have been studying organic copolymers for use in OPV devices now, and just need to clarify a few questions hanging about my mind..
1) i understand that the longer the conjugation length in a polymer, the lower the energy of the photon it is able to absorb (the higher the wavelength of light it is able to absorb). however, i have gotten some experimental data that seems to prove otherwise.. i have copolymer units with anthracene, naphthalene and phenylene (lets call them A, N and P respectively). my data shows that the maximum absorption decreases from P->N->A. i don't get it - isn't the trend supposed to be the other way round (ie, maximum absorption increases from P->N->A)?
2) i always read about the absorption of photon energy, and that as long as the photon has enough energy to overcome the energy barrier between the HOMO and LUMO energies, the substance will be able to absorb the light. what does this mean? does it mean that photons with energy ABOVE the barrier will also be absorbed, just that the excess energy will be "wasted" (returned back to surroundings thru other processes like releasing heat)? or does it mean that only photons with the EXACT energy as the energy barrier can be absorbed?
all help is appreciated :)
I am doing some of my own studies on OPV devices (i'm still a high school student, so I have no prior research experience of in-depth knowledge on processes that take place at the atomic level during the operation of the device). i have been studying organic copolymers for use in OPV devices now, and just need to clarify a few questions hanging about my mind..
1) i understand that the longer the conjugation length in a polymer, the lower the energy of the photon it is able to absorb (the higher the wavelength of light it is able to absorb). however, i have gotten some experimental data that seems to prove otherwise.. i have copolymer units with anthracene, naphthalene and phenylene (lets call them A, N and P respectively). my data shows that the maximum absorption decreases from P->N->A. i don't get it - isn't the trend supposed to be the other way round (ie, maximum absorption increases from P->N->A)?
2) i always read about the absorption of photon energy, and that as long as the photon has enough energy to overcome the energy barrier between the HOMO and LUMO energies, the substance will be able to absorb the light. what does this mean? does it mean that photons with energy ABOVE the barrier will also be absorbed, just that the excess energy will be "wasted" (returned back to surroundings thru other processes like releasing heat)? or does it mean that only photons with the EXACT energy as the energy barrier can be absorbed?
all help is appreciated :)
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