Magnetic Field Effects of Charge Transfer Excitons in Organic Semiconductor Devices

The topic of this review is the effect of magnetic field on photo-current (PC) in organic semiconductor devices. Magnetic field modifies the fraction of the singlet/triplet population in the charge transfer excitons (CTE) whose lifetime is spin configuration dependent yielding magneto-PC (MPC). We review MPC in the framework of the polaron pair model and emphasize the effect of CTE lifetime on MPC. In addition to a detailed calculation of the MPC response we find a range of physical parameters in which the response follows a simple ' fit function '. For example, a sum of wide and narrow Lorentzian functions, MPC(B)=c(w)B(2)/(B-2+b(w)(2))+c(n)B(2)/(B-2+b(n)(2)), in the case of hyperfine interaction; or a Voigt profile V=L*G, where the sign * stands for the convolution operation between a Lorentzian (L) and a Gaussian (G) functions, in the case of thermal spin polarization. We provide expressions for the fit parameters in terms of physical parameters.