Abstract
AbstractNanoscale chemical analysis of functional polymer systems by electron microscopy, to gain access into degradation processes during the materials life cycle, is still a formidable challenge due to their beam sensitivity. Here a systematic study on the different stages of degradation in a P3HT‐PCBM organic photovoltaic (OPV) model system is presented. To this end pristine samples, samples with (reversibly) physisorbed oxygen and water and samples with (irreversibly) chemisorbed oxygen and water are imaged utilizing the full capabilities of cryogenic STEM‐EELS. It is found that oxygen and water are largely physisorbed in this system leading to significant effects on the band structure, especially for PCBM. Quantification proves that degradation concomitantly decreases the amount of CC bonds and increases the amount of COC bonds in the sample. Finally, it is shown that with a pulsed electron beam utilizing a microwave cavity, beam damage can be significantly reduced which likely extends the possibilities for such studies in future.
Highlights
To make the transition from fossil fuels to renewable energy, new materials for energy generation, conversion, and storage are necessary
As we have previously shown, cryogenic STEM-EELS is preferred over energy filtered TEM and STEM-EDX to quantitatively analyze oxygen and water uptake across P3HTPCBM interfaces of columnar model systems.[19]
To assess changes in chemical bonding, the shape of the oxygen K-edge and carbon K-edge are analyzed, before HR-EELS results are shown assessing the effects of oxygen and water physisorption and chemisorption on the band structure of P3HT and PCBM
Summary
To make the transition from fossil fuels to renewable energy, new materials for energy generation, conversion, and storage are necessary. To assess changes in chemical bonding, the shape of the oxygen K-edge and carbon K-edge are analyzed, before HR-EELS results are shown assessing the effects of oxygen and water physisorption and chemisorption on the band structure of P3HT and PCBM. The oxygen concentration in the degraded and glovebox sample seem similar, especially in the PCBM-rich region (at negative positions).
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