Time-dependent geminate recombination in the presence of disorder in the energy of the hopping sites

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Abstract
Applying the Monte Carlo technique, we have simulated the time decay of a reservoir of geminate electron—hole pairs for one- and three-dimensional lattices where the site energies are subject to a Gaussian distribution of width σ. As a result of disorder the recombination spectra shift towards longer times, broaden, and lose their power-law decay pattern. The average recombination time [τr] scales with exp (σ/T)2. This behaviour reflects dispersive motion of the carriers within their mutual Coulombic well. A relationship is proposed that allows one to predict [τr] once the dispersive parameter α for the transport process is known, independent of the type of distribution of hopping sites. Comparison is made with experimental data for a-Si: H and a-As2S3.