Solar cells organic

The aim of this chapter is to give a state-of-the-art report on the plastic solar cells based on conjugated polymers. Results from other organic solar cells like pristine fullerene cells [7, 8], dye-sensitized liquid electrolyte [9], or solid state polymer electrolyte cells [10], pure dye cells [11, 12], or small molecule cells [13], mostly based on heterojunctions between phthaocyanines and perylenes [14], will not be discussed. Extensive literature exists on the fabrication of solar cells based on small molecular dyes with donor-acceptor systems (see for example [2, 3] and references therein). 

Figure 3.31. Organic solar cell with the molecular glass Spiro-MeOTAD as the solid-state electrolyte. The photosensitive ruthenium dye is attached as a monolayer to Ti02 nanoparticles, thus forming a large active area for photoinduced electron transfer.

X. Wang, L. Zhi, N. Tsao, Z. Tomovic, J. Li, K. Mullen, Transparent carbon films as electrodes in organic solar cells, Angewandte Chemie (International Ed. in English), 47 (2008) 2990-2992. 

Fig. 17.5 Scheme of basic processes occurring in DSSCs (a) and organic solar cells (c). (b) Band bending for an n-type semiconductor and a p-type semiconductor in equilibrium with an electrolyte. 

Li, G. Liu, L., Carbon nanotubes for organic solar cells. Nanotechnology Magazine, IEEE 2011, 5,18-24. 

Through exothermic dissociation of a neutral excited state in molecule by electron transfer to an adjacent molecule. This process leads to the generation of geminately bound electron-hole pairs as precursors of free positive and negative charges in an organic solar cell. 

Bredas JL, Norton JE, Comil J, Coropceanu V (2009) Molecular understanding of organic solar cells the challenges. Acc Chem Res 42 1691... 

Wu J, Becerril HA, Bao Z et al (2008) Organic solar cells with solution-processed graphene transparent electrodes. Appl Phys Lett 92 263302/1-263302/3... 

Keywords Charge-transfer state Organic electronics Organic solar cells Photovoltaics Solar energy... 

Fig. 3 Contemporary organic solar cell devices are based on donor/acceptor heterojunction device architectures, (a) Energy level diagram, (b) Planar heterojunction conligmation. (c) Bulk heterojunction configuration...

Fig. 4 Schematic illustration of the processes leading to photocurrent generation in organic solar cells, (a) Photon absorption in Step 1 leads to excitons that may diffuse in Step 2 to the donor/ acceptor (D/A) interface. Quenching of the exciton at the D/A interface in Step 3 leads to formation of the charge-transfer (CT) state. Note that processes analogous to Steps 1-3 may also occur in the acceptor material, (b) Charge separation in Step 4 leads to free polarons that are transported through the organic layers and collected at the electrodes in Steps 5 and 6, respectively, (c) The equilibria involved in Steps 1-4- strongly influence device efficiency...

Fig. 8 Schematic illustration of donor/acceptor energies relevant for charge-transfer in organic solar cells. Straight lines represent ground state binding energies, while wavy lines represent excited state binding energies...

The preceding sections described molecular interactions important in organic solar cells. This section discusses the impact of those interactions on the overall device behavior. Simulated electrical behavior for a typical solar cell is illustrated in Fig. 10. Under forward bias voltages 0 < V < Vqo typical photovoltaic device under illumination supplies power (P = / x V) to the external circuit (cf. lower panel of Fig. 10, dashed trace in first quadrant). The formalism used here implies that, under reverse bias, the organic material is reduced at the anode and oxidized at the cathode, while, under forward bias, the organic material is oxidized at the anode and reduced at the cathode. The short circuit current, J c, is approximately equal to... 

In organic solar cells, the chemical potential must be considered in addition to the electrical potential. For example, the magnitude and polarity of the photovoltage produced by the first modem donor/acceptor OPV device [9] was noted to... 

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...

Fig. 16 Parameters for defining the charge-transfer state energy cx in organic solar cells. Charge-transfer state energy for MDMO-PPV PCBM blend device determined by Fourier transform photocurrent spectroscopy and electroluminescence measurements. Reprinted figure with permission from [188]. Copyright 2010 by the American Physical Society...

Heremans P, Cheyns D, Rand BP (2009) Strategies for increasing the efficiency of heterojunction organic solar cells material selection and device architecture. Acc Chem Res 42 1740... 

Wynands D, Levichkova M, Riede M, Pfeiffer M, Baeuerle P, Rentenberger R, Dernier P, Leo K (2010) Correlation between morphology and performance of low bandgap oligothiophene C6o mixed heterojunctions in organic solar cells. J Appl Phys 107 6... 

Hoppe H, Sariciftci NS (2004) Organic solar cells an overview. J Mater Res 19 1924... 

Steim R, Kogler FR, Brahec CJ (2010) Interface materials for organic solar cells. J Mater Chem 20 2499... 

Clarke TM, Durrant JR (2010) Charge photogeneration in organic solar cells. Chem Rev... 

Rand BP, Schols S, Cheyns D, Gommans H, Girotto C, Genoe J, Heremans P, Poortmans J (2009) Organic solar cells with sensitized phosphorescent absorbing layers. Org Electron 10 1015... 

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