Polymer:fullerene blends

Fig. 15 Charge-transfer state electroluminescence (EL) for several polymer fullerene blends used in donor/acceptor organic solar cells. Adapted with permission from [184]. Copyright 2009 American Chemical Society...

Lee J, Vandewal K, Yost SR, Bahlke ME, Goris L, Baldo MA, Manca JV, Van Voorhis T (2010) Charge transfer state versus hot exciton dissociation in polymer-fullerene blended solar cells. J Am Chem Soc 132 11878... 

Hallermann M, Haneder S, Da Como E (2008) Charge-transfer states in conjugated polymer/ fullerene blends below-gap weakly bound excitons for polymer photovoltaics. Appl Phys Lett 93 053307... 

Zhou Y, Tvingstedt K, Zhang EL, Du CX, Ni WX, Andersson MR, Inganas O (2009) Observation of a charge transfer state in low-bandgap polymer/fullerene blend systems by photoluminescence and electroluminescence studies. Adv Funct Mater 19 3293... 

Application of Pump—Probe Spectroscopy in the ms Range to Conjugated Polymer/Fullerene Blends... 

Consequently, the excited state absorption pattern of the polymer/fullerene blend mirrors the absorption of the photoinduced charge carriers, as outlined in the introduction. 

A bulk heteroj unction is by definition a blend of p-type and n-type semiconductors (donor/acceptor). As a prototype bulk heteroj unction, we shall discuss the properties of polymer/fullerene blends. Apart from the poly-... 

Several organics, e.g. pristine poly(3-octylthiophene), polyfluorene, bifunctional spiro compounds and polyphenyleneethynylene derivative, have been used for fabricating photOFETs. Responsivity as high as 0.5-1 A/W has been achieved in some of these transistors. We have already discussed the bulk heterojunction concept in Chapter 5. The bulk heterojunctions are fabricated using acceptor materials with high electron affinity (such as C<5o or soluble derivatives of C6o) mixed with conjugated polymers as electron donors. PhotOFETs based on conjugated polymer/fullerene blends are expected to show... 

N. Marjanovic, et al., Photoresponse of organic field-effect transistors based on conjugated polymer/fullerene blends, Organic Electronics 1 (2006) 188-194. 

Campoy-QnUes M., Ferenczi T., Agostinelli T., Etchegoin P., Kim Y., Anthopoulous T., Stavrinon P. N., Bradley D. D. C. and Nelson J. (2007), Self-organisation and lateral and vertical diffnsion in polymer fullerene blends from fabrication protocols to molecnlar dynamics , in preparation. 

Goris L., Poruba A., Hod akova L., Vanecek M., Haenen K., Nesladek M., Wagner P., Vanderzande D., de Scheppe, L. and Manca J. V. (2006), Observation of the subgap optical absorption in polymer-fullerene blend solar cells , Appl. Phys. Lett. 88, 052113. 

Exciton diffusion and dissociation in conjugated polymer/fullerene blends and heterostructures. Phys. Rev. B, 59, pp. 15346-15351. 

Fig. 13 Effect of insertion of LiF layers of different thickness between the polymer-fullerene blend and the aluminum electrode. The current-voltage characteristics indicate a more effective charge carrier injection (a), and as can be seen also from b and c, the fill factor as well as the open circuit voltage profit from LiF. (Reprinted with permission from [91], 2002, American Institute of Physics)...

Use of high-resolution scanning electron microscopy (SEM) allowed the uncovering of a further substructure in these polymer-fullerene blends, besides some larger fullerene clusters (see Fig. 24) MDMO-PPV nanospheres representing a coiled polymer conformation were detected together with some solvent-dependent amount of PCBM fullerenes [55,60-62,137]. 

In conclusion, not only the observed larger scale of phase separation but also the difference in the material s phase percolation and thus charge transport properties influence the photovoltaic performance. As such, it becomes evident that the charge carrier mobility measured in these devices must be a function of the blend morphology [139-143]. Furthermore, the electron and hole carrier mobilities depend strongly on the polymer-fullerene blending ratio. Interestingly, the hole mobility of the donor polymer is increased considerably in blends with fullerenes (see Fig. 27) [142,144-147]. 

Charge recombination in conjugated polymer/fullerene blended films studied by transient absorption spectroscopy. J Phys Chem B 107 1567... 

Nelson J (2003) Diffusion-limited recombination in polymer-fullerene blends and its influence on photocurrent collection. Phys Rev B 67 155209... 

Haugeneder A, Neges M, Kallinger C, Spirkl W, Lemmer U, Feldmann J, Scherf U, Harth E, Giigel A, Mullen K (1999) Exciton diffusion and dissociation in conjugated polymer/fullerene blends and heterostructures. Phys Rev B 59 15346... 

Riedel I, Dyakonov V (2004) Influence of electronic transport properties of polymer-fullerene blends on the performance of bulk heterojimction photovoltaic devices. Phys Status Solidi A 201 1332... 

Next, we studied the magneto-transport properties on the conjugated polymer/ fulleiene BHSC. In a BHSC, a polymer - fullerene blend is used, where fullerenes having higher electron affinity attract electrons in it and holes are left on the polymer chains. Thus, electron and hole pathways are separated givinga lower probability of e-h pairs to be formed. 

Photo-induced changes in the complex index of refraction in conjugated polymer/fullerene blends have been reported [148]. 

Park, L.Y., Mrmro, A.M., Ginger, D.S. Controlling film morphology in conjugated polymer fullerene blends with surface patterning. J. Am. Chem. Soc. 130, 15916-15926 (2008)... 

N. Marjanovic, T. B. Singh, G. Dennler, S. Giines, H. Neugebauer, N. S. Sariciftci, R. Schwodiauer, S. Bauer, Photoresponse of Organic Field-Effect Transistors Based on Conjugated Polymer/Fullerene Blends. Org. Electron. 2006,7, 188-194. 

A. Haugeneder, M. Neges, C. Kalhnger, W. Spirkl, U. Lemmer, J. Feldmann, U. Scherf, E. Harth, A. Giigel, K. Mullen, Exciton Diffusion and Dissociation in Conjugated Polymer/Fullerene Blends and Heterostructures. Physical Review B 1999,59,15346-15351. 

V.S. Gevaerts, et al. Solution processed polymer tandem solar cell using efficient small and wide bandgap polymer fullerene blends. Advanced Materials, 2012 p. 1-5. 

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