Organic solar cells polymer bilayer devices

As shown in Figure 5.9, randomly mixed polymer-inorganic BHJ and ordered heterojunction (OHJ) are two common structures to prepare hybrid solar cells [44]. Similar to polymer-fullerene BHJ solar cells, polymer-inorganic hybrid BHJ solar cells (Figure 5.9a) can overcome the limitations of bilayer devices having small donor-acceptor interfacial area with inefficient exciton dissociation. NCRs can be surface modified to render them soluble in organic solvents (such as chloroform, toluene and chlorobenzene) to facilitate solution processability. Various surface... 

The chapter is organized as follows the second section will discuss the photophysics of conjugated polymer/fullerene composites as a standard model for a charge-generating layer in plastic solar cells. Pristine polymer devices will be discussed in the third section while bilayer and interpenetrating network devices are presented in Sections 4 and 5. Section 6 contains some remarks on large area plastic solar cells and Section 7 conclusions. 

An alternative inexpensive organic polymer-based photovoltaic solar cell has been invented. In this device, p-type and n-type semiconductors are sequentially stacked on top of each other. In such devices, absorption of a photon by a ji-conjugated polymer results in the formation of an excited state, where coulom-bicaUy bound electron-hole pair (exciton) is created. This exciton diffuses to a region of interface of n-type semiconductor where exciton dissociation takes place and transport of charge to the respective electrodes occurs. For example, the photo-induced electron transfer from a donor layer (p-type) to acceptor layer (n-type) takes place in a polymer/fullerene-based organic bilayer solar cell, MDMO-PPV PCBM, with power conversion efiiciency of 2.5 % (Fig. 11.8) [13]. 

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