Organic solar cell charge transport

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...

N. Adhikari, et al. Device and morphological engineering of organic solar cells for enhanced charge transport and photovoltaic performance. Journal of Photonics for Energy, 2015. 5(1) p. 057207-057207. 

The RRE approach has successfolly been applied to extract stacking distances in a perylene tetracarboxydiimide derivative, Cgj-PDI [86]. The supramolecular arrangement of these PDI derivatives allows for ID electronic charge transport, an attractive property for the fabrication of nanoscale devices such as organic solar cells. 

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. 

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