C60: A host lattice for the intercalation of oxygen?

Abstract

Abstract. The investigation of structural and electronic properties of the novel family of fullerenes depends on the existence of pure reference materials. Sublimation of the van-der Waals solids is a suitable purification method. Little attention has been paid to the question about the air stability of such sublimed samples in form of crystals or thin films. A combination of thermat desorption spectroscopy, thermal analysis and diffuse reflectance FT-IR spectroscopy is used to show the extent to which oxygen from dry air is intercalated into fullerenes and which detrimental reactivity occurs from attempts to thermally remove (,,anneal") air-exposed samples. The conclusion is that any fullerene sample exposed to air will be transformed in part into a polymeric non-fullerene carbon upon thermal treatment to above 400 K irrespective of its initial purity.

Suppression of Time‐Dependent Donor/Acceptor Interface Degradation by Redistributing Donor Charge Density

“…bonding). [ 12,[34][35][36] This observation is in good agreement with our XPS results which show boride bond formation between SubPc and C 60 upon aging. However, it is interesting to note that the MoO 3 /SubPc/C 60 device in Figure 4 c show limited (2%) and negligible (0%) drop in main signal peaks of both C 60 and SubPc respectively.…”

Impact of intentional photo-oxidation of a donor polymer and PC70BM on solar cell performance

“…The mechanism for the loss of conjugation due to the breaking of CQC bonds in the PC 70 BM cage is similar to what has been previously established for PC 60 BM, both theoretically by Brumboiu et al 48,54 and experimentally by Anselmo et al 25 The breaking of CQC bonds may also lead to the opening of the C 70 cage. 17 In contrast to the TQ1:PC 60 BM blend (Hansson et al 27 ), the presence of TQ1 decelerates the photo-oxidation of the PC 70 BM component in the TQ1:PC 70 BM blend. Given the slightly lower rate of photo-oxidation for PC 70 BM as compared to PC 60 BM, 26 this then implies that the TQ1:PC 70 BM blend must be more stable against photo-oxidation than the TQ1:PC 60 BM blend.…”

“…Wohlers et al 16 showed that thermal heating of C 60 and C 70 in an oxygen atmosphere induces the formation of a sequence of oxidation products, even in the dark. This sequence of oxidation products of fullerenes, proposed by Wohlers et al, 17,18 starts with the formation of epoxides and carbonyls, followed by the formation of dicarbonyl and anhydride groups on the fullerene cage, accompanied by cage opening. The growth of carbonyl products in fullerene derivative PC 60 BM thin films, as observed by FT-IR, was reported by Chambon et al 19 Eklund et al 20 showed the oxidation of the fullerene cage in the presence of UV and visible light.…”

“…6c) shows that the surfaces and near surface regions of the PC 70 BM films are affected much more rapidly than the bulk by exposure of the films. This indicates that the PC 70 BM molecules in the film surface lose their conjugated character early in the exposure process (within the first 30 minutes) due to the breaking of the CQC bonds of the cage, 17,49 which allows the formation of photo-oxidation products. This early carbonyl formation after 15 min exposure is not directly observable in the FT-IR absorption spectrum (Fig.…”

Study of oxygen-C 60 compound formation by NEXAFS and RIXS

“…4 orders of magnitude) increase in the resistivity of C 60 upon oxygen exposure (intercalation), followed by a slight decrease after a heating cycle in vacuum to 630 K to desorb the oxygen. However, when annealing a C 60 sample, the de-intercalation of the contained oxygen competes with further reaction of oxygen with the fullerite, which ultimately leads to the opening and breaking of the C 60 cages [2,20]. The processes are similar when the sample is exposed to UV-light [3,21,22] instead of heating.…”