Conjugated polymer:fullerene bulk heterojunction solar cells

A significant increase in the forward current and in the FF is observed for conjugated polymer/fullerene bulk heterojunction solar cells upon insertion of a thin layer of LiF between the organic layer and the Al electrode (negative electrode of the solar cell), as shown in Fig. 5.37a and b. 

The observed experimental result that Voc decreases linearly for bulk heterojunction solar cells allows us to conclude that, at least in the high temperature range (T > 200 K), these solar cells may be described by a diode model with Ip exp(E/kT). Here E is a parameter analogous to Eg for conventional semiconductors. For conjugated polymer/fullerene bulk heterojunction solar cells, E should correspond to the energy difference between the HOMO level of the donor and the LUMO level of the acceptor components of the active layer [as also suggested by the extrapolated value of V oc(0 K)]. 

Mozer, A.J., G. Dennler, N.S. Sariciftci, M. Westerling, A. Pivrikas, R. Osterbacka, and G. Juska. 2005. Time-dependent mobility and recombination of the photoinduced charge carriers in conjugated polymer/fullerene bulk heterojunction solar cells. Phys Rev B 72 035217. 

Hoppe H, Glatzel T, Niggemann M, Hinsch A, Lux-Steiner MC, Sariciftci NS (2005) Kelvin probe force microscopy study on conjugated polymer/fullerene bulk heterojunction organic solar cells. Nano Lett 5 269... 

Hoppe H, Arnold N, Meissner D, Sariciftci NS (2004) Modeling of optical absorption in conjugated polymer/fullerene bulk-heterojunction plastic solar cells. Thin Solid Eilms 451-452 589... 

Fullerene/polymer organic bulk heterojunction solar cells have very simple architecture (Figure 47a). To make such devices, fullerene derivative and a conjugated polymer are dissolved together in an appropriate solvent. The resulting solution is deposited on a conducting substrate... 

Hoppe H, Niggemann M, Winder C, Kraut J, Hiesgen R, Hinsch A, Meissner D, Sariciftci NS (2004) Nanoscale morphology of conjugated polymer/fullerene based bulk-heterojunction solar cells. Adv Fund Mater 14 1005... 

H. Hoppe, M. Niggemann, C. Winder, J. Kraut, R. Hiesgen, A. Hinsch, D. Meissner, N. S. Sariciftci, Nanoscale Morphology of Conjugated Polymer/ Fullerene-Based Bulk-Heterojunction Solar Cells. Adv. Funct. Mater. 2004, 14, 1005-1011. 

Usually, the photoactive layer of bulk heterojunction solar cells is a physical blend [1-3] of a rr-conjugated polymer [12] and a fullerene derivative [13-17]. This bulk heterojunction structure inspired the design and preparation of donor... 

Hoppe, H., N. Arnold, N.S. Sariciftci, and D. Meissner. 2003. Modeling the optical absorption within conjugated polymer/fullerene-based bulk-heterojunction organic solar cells. Sol Ener Mater Sol Cells 80 105. 

It is the purpose of this chapter to introduce photoinduced charge transfer phenomena in bulk heterojunction composites, i.e., blends of conjugated polymers and fullerenes. Phenomena found in other organic solar cells such as pristine fullerene cells [11,12], dye sensitised liquid electrolyte [13] or solid state polymer electrolyte cells [14], pure dye cells [15,16] or small molecule cells [17], mostly based on heterojunctions between phthalocyanines and perylenes [18] or other bilayer systems will not be discussed here, but in the corresponding chapters of this book. 

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