The Negative Effect of High‐Temperature Annealing on Charge‐Carrier Lifetimes in Microcrystalline PCBM

Abstract

The fullerene derivative, phenyl-C 61 -butyric acid methyl ester (PCBM) has been the subject of intense recent study as the electron-acceptor component in heterojunction blends for all-organic photovoltaic devices (OPVs) [1][2][3][4][5][6][7][8][9][10] and as the electron-transport layer in organic field-effect transistors (FETs). [11][12][13][14][15][16] In most of the studies referenced, the effect of high-temperature annealing has been investigated and has usually been found to have a positive influence on device characteristics, including the external quantum efficiency of OPVs and the electron mobility in FETs. This has been attributed to reorganization and/or aggregation within the initially amorphous or nanocrystalline spin-cast films resulting in the formation of larger well-organized domains. The occurrence of PCBM aggregation to form microcrystallites on annealing of spin-cast films has been well-documented by atomic force and electron beam microscopy studies of polymer blends with high PCBM content [7][8][9]17,18] and pure PCBM films.

Time‐Dependent Morphology Evolution by Annealing Processes on Polymer:Fullerene Blend Solar Cells

“…4c), an observation also confirmed by considering the nearly unchanged SAED patterns of both images of Figure 7a and b. [17] Figure 8 shows the device performances of BHJ solar cells with P3HT:PCBM active layers fabricated by several time-dependent annealing treatments. In spite of this, the PCBM molecules that remained outside the P3HT crystalline domain may have aggregated with each other.…”

Pump‐Probe Spectroscopy in Organic Semiconductors: Monitoring Fundamental Processes of Relevance in Optoelectronics

“…Its application in systems which exhibit short range order enables to characterize early charge transport within nanometer-size domain regions, having a great potential for monitoring transport on a variety of nanoscopic media such as polymer chains, carbon nanotubes, or molecular aggregates. ), [ 106 ] although comparison in this case is not straight forward owing to different experimental conditions involved in these two techniques.…”

The Mobility and Decay Kinetics of Charge Carriers in Pulse-Ionized Microcrystalline PCBM Powder

“…Since trapping and/or chemical degradation of the material may be associated with the presence of oxygen, subsequent experiments have been carried out in which the sample could be rigorously evacuated. [40] The results will be presented in a subsequent publication.…”