Phase P3HT: PCBM

Structural instability due to phase segregation in donor-acceptor blends over time is a function of materials and temperature. At moderate temperatures of 50-80 C, the problem is more severe in MDMO-PPV PCBM than P3HT PCBM blend films. This... 

J. Zhao, A. Swinnen, Van G. Assche, J. Mcuicci, D. Vcuiderzande, B. V. Mele, Phase Diagram of P3HT/PCBM Blends cuid Its Implication for the Stability of Morphology. J. Phys. Chem. B 2009,113,1587-1591. 

B.A. Collins, J.R. Tumbleston, and H. Ade, Miscibility, crystallinity, and phase development in P3HT/PCBM solar cells Toward an enlightened understanding of device morphology and stability. The Journal of Physical Chemistry Letters, 2011. 2(24) p. 3135-3145. 

The P3HT/PCBM bulk heterojunction device remained stable for 1000 h with less than 20% change in the device parameters tested at elevated temperatures, which indicates that both the chemical stability of the materials and the stability of the phase-separated network are promising for long-term operation [63]. Using encapsulation techniques, the stability of the devices can be improved to beyond 3000 h [64]. 

Figure 2.12 Volume representation obtained by electron tomography of P3HT nanorods (bright phase) in a P3HT/PCBM bulk heterojunction demonstrating the presence of a genuine 3D co-continuous network and concentration gradients within the thickness of...

Nieuwendaal et al. showed that because of spin diffusion, NMR sensitivity to intermolecular correlations at the nanometer length scale, and its unambiguous chemical contrast, can be used to measure the phase behavior and domain sizes of BHJs of the P3HT/PCBM system [52]. When increasing the efficiency of OPVs, thermal treatment is generally thought of as a vital step in fabrication process however, the formation of needle-like PCBM crystallites which normally cause a lower effidency is one unfortunate consequence of thermal treatment. 

Fig. 9 Two component nonequilibrium phase diagram for P3HT PCBM measured using differential scanning calorimetry. Reprinted (adapted) with permission from [121]. Copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim...

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