Functional cell states

Despite the lack of theoretical models for interfacial recombination processes in excitonic solar cells, it is obvious empirically that those cells which function efficiently must have a very slow rate of recombination. In DSSCs, this can be explained simply by the slow electron self-exchange rate of the I /I2 redox couple and the absence of field-driven recombination. However, in the case of solid-state, high-surface-area OPV cells, such as the conducting polymer/C60-derivative cells [36,39], the slow rate of interfacial recombination is an important problem that is not yet understood. 

The enthalpy change associated with a cell reaction is a state function and hence is independent of whether the reaction is being carried out reversibly or not. If an exothermic reaction is carried out completely irreversibly, the total enthalpy change AH will appear as heat given out to the surroundings ... 

The galvanic cell performs an electric work when the electrochemical reaction of the cell occurs. As work is not a state function, the amount of work which a system does depends on the path it takes for given initial and final states. Under what conditions does the amount of work the cell performs become maximum ... 

Hess s law in going from a particular set of reactants to a particular set of products, the enthalpy change is the same whether the reaction takes place in one step or in a series of steps in summary, enthalpy is a state function. (9.5) Heterogeneous equilibrium an equilibrium involving reactants and/or products in more than one phase. (6.5) Hexagonal closest packed (hep) structure a structure composed of closest packed spheres with an ababab arrangement of layers the unit cell is hexagonal. (16.4)... 

For consistency, pseudopotentials should be based on the same functionals as used for the valence states. This point has been illustrated by Gale and coworkers in their study of aluminum trihydroxides [47]. Table 8.3 compares their results of cell optimizations using various mixtures of psuedopotential and valence state functionals with the experimental structure of gibbsite [48]. LDA pseudopotentials in an LDA optimization of the cell gives underestimated cell parameters, consistent with the usual expectation that LDA gives over-binding in chemical bonds. 

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