Photovoltaic device donor material

Photovoltaic Devices with OPV4—Ceo- The increased lifetime of the charge-separated state, which extends into the millisecond time domain, opens the possibility of using the OPVrt-Coo dyads as the active material in a photovoltaic device. As an important difference with previous bulk heterojunction cells, the covalent linkage between donor and acceptor in these molecular dyads restricts the dimensions of the phase separation between the oligomer and the fullerene that could freely occur in blends of the individual components. This can be considered as a primitive attempt to obtain more ordered and better-defined phase-separated D-A networks. 

It is certain that electrically conductive polymers have attracted much attention in the field of solid state science in recent years. They are expected to have convenient function in the production of useful electric or electronic devices such as the electrodes in rechargeable batteries, pn-junctions for use in integrated circuits (ICs) or in photovoltaic devices, and so on. In the normal sense, the organic polymers, even the 7r-conju-gated systems having mobile 7r electrons, are typical insulators of poor electrical conductivity and have been utilized as dielectric material. This is considered to be a result of the Peierls transition (Peierls, 1955), namely, a metallic-insulator transition, e.g., for polyacetylene, which is characteristic in the one-dimensional system. This situation is circumvented by the doping technique, in which the electron acceptors or donors... 

Gebeyehu, D., Maennig, B., Drechsel, J., Leo, K., and Pfeiffer, M. 2003. Bulk-heterojunction photovoltaic devices based on donor-acceptor organic small molecule blends. Solar Energy Materials and Solar Cells 79 (l) 81-92. 

As common in semiconductors, the material or the composite material, respectively, must provide both electron donor and electron acceptor properties. In photovoltaic devices, the absorption of light effects the separation of electric charges that are flowing to the electrodes and are building up a difference of electric potential. 

Electrochemical reaction usually consists of a blend of two materials an electron-donor TT-conjugated polymer (donor, D) and an electron-acceptor fullerene derivative (acceptor, A). Polymers with electrochemical properties have attracted considerable attention over past decades due to potential applications in various fields including low-cost, lightweight, and flexible electrode materials in photovoltaic devices, such as, solar cells and energy storage devices like supercapacitors (Ripolles-Sanchis et al., 2013 Gelinck et al, 2010 Snook etal, 2011). 

Working in collaboration with Reynolds, we have fabricated organic photovoltaic devices in which the active materials were assembled by using the LbL method [53]. In this work, the donor and hole transporting materials were the anionic CPEs PPE-SOs and PPE-EDOT-SO , whereas the acceptor and electron transport material was a cationic fullerene derivative, Cso-NHa (Scheme 14.13). The active layers were constructed atop an ITO substrate that was precoated with a PEDOT-PSS film (spin-coated). The PPE(—)/C6o—NHa bilayers were deposited through the LbL method, and the effect of active layer thickness on device performance was explored. Figure 14.20 shows a schematic... 

Due to the successful use of PCBM as acceptor material in solar cells, various attempts have been made to link Ceo covalently to an oligothiophene backbone in order to prepare D-A-based materials for photovoltaic devices by tuning their electronic properties [45, 46, 200, 201]. The attachment of fullerene units prevented large-scale phase separation in thin films and, despite the inclusion of bulky fullerene units, the soluble polymers retained their high order in thin films. However, the efficiency of such devices has been limited by competition between photoinduced electron transfer and energy transfer which occurs from the donor component to the fullerene. 

These problems may be overcome by the use of organic photovoltaic solar cells [117-120], which consist of a donor and an acceptor material, each possessing its individual HOMO and LUMO energy levels. For an efficient device configuration, the HOMO and LUMO energy levels of the donor material must be higher com-... 

Working principles of organic solar cells are well described in a recent review and some monographs. More or less all types of organic solar cells described above comprise two components in the photoactive layer. One component serves as electron donor, whereas the other works as electron acceptor. Absorption of photons by the active layer components results in the electron transfer from donor to acceptor. This process called photoinduced charge transfer is a fundamental principle of operation of all known organic photovoltaic devices as well as the natural photosynthetic systems. In many cases, donor material is capable of efficient p-type transport and therefore can be called as p-type organic semiconductor. At the same time, electron acceptor material is denoted as n-type semiconductor in many cases. 

---