Valence and Conduction Band States of PCBM as Probed by Photoelectron Spectroscopy at Resonant Excitation

Abstract

We have studied (6,6)-phenyl C 61 butyric acid methyl ester by near-edge X-ray absorption fine structure and resonant synchrotron radiation X-ray photoelectron spectroscopy. We determine the binding/hybridization character of the participating valence and conduction band states involving π* or σ* empty conduction band states. The analysis of the resonant Auger processes delivers a powerful tool to distinguish σ* and π* states in organic sp 2 hybridized systems. For the σ* states, we find the conventional KLL Auger process creating a C2p 4 final state. However, for the π* features right at the resonance, we identify a novel Auger decay mechanism. We attribute this process to the decay of an excitonic intermediate state with a long lifetime which causes a three-hole (C2p 3 ) final state.

Correlating Three‐dimensional Morphology With Function in PBDB‐T:IT‐M Non‐Fullerene Organic Solar Cells

“…All spectra were recorded using a charge neutralizer to limit differential charging. The main carbon peak is charge referenced to 284.5 eV . The method of XPS for depth profiles and calculating component is shown in supporting information.…”

Use of gas cluster ion source depth profiling to study the oxidation of fullerene thin films by XPS

“…For fresh, asproduced, PC 61 BM surfaces a sharp main peak centred at 284 eV is observed, along with several smaller peaks (Figure 2a and Table 1). These have previously been observed in synchrotron studies as being from the oxygenated carbon species in the ester group on the PC 61 BM side-chain, with the broad π→π* loss peak that is characteristic of sp 2 hybridised systems [49]. A slight excess of O=C-O is noted over the expected 1.4%.…”

“…GL(70) -GL(80) will more adequately models the edge of the pristine PC 61 BM between ~283-282 eV. We also initially constrained the relative positions of peaks in the O(1s) and C(1s) envelopes as observed elsewhere [49], noting that our main C(1s) peak is observed at 284.0 eV and not 285.3 eV. Similarly, the FWHM of the photoelectron peaks, not including the broad high energy π-π* shake up feature, were initially constrained so that all were equal.…”

Impact of processing on the chemical and electronic properties of phenyl-C61-butyric acid methyl ester

“…19) but has also been assigned to the side chain. 20,21 To evaluate the differences of the C 60 and PCBM C1s spectra further, the emission lines are also represented normalized to their maximum intensity in Fig. 2b.…”