Atomistic Approach To Simulate Processes Relevant for the Efficiencies of Organic Solar Cells as a Function of Molecular Properties. II. Kinetic Aspects

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• 作者：Charlotte Brückner ; Frank WürthnerKlaus Meerholz ; Bernd Engels
• 刊名：Journal of Physical Chemistry C
• 出版年：2017
• 出版时间：January 12, 2017
• 年：2017
• 卷：121
• 期：1
• 页码：26-51
• 全文大小：2028K
• ISSN：1932-7455

文摘

The individual steps of the light-to-energy conversion process in the vicinity of the interfaces of organic solar cells are investigated with kinetic Monte Carlo simulations employing Marcus hopping rates obtained from quantum-chemical calculations. A chemically diverse set of p-type semiconducting molecules in heterojunction with fullerene C₆₀ is used. Starting with exciton diffusion, exciton dissociation, charge generation, and charge separation are modeled on an atomistic level. Numerous aspects were already analyzed, but comprehensive simulations including all three processes in amorphous model interface systems and a comparison of various different molecular p-type semiconductors seem to be missing. Our investigation identifies several important kinetic effects that could limit device efficiencies, such as the strong reduction of charge transport rates in the vicinity of the interface due to Coulomb interactions between the charges, the importance of adjusting the relative rates of exciton transfer and dissociation, and the impact of morphology. Charge drift velocities and hole mobilities obtained from the simulations compare well with experimental values indicating that the main effects are covered by the simulations. A correlation between experimental short-circuit currents and simulated charge drift velocities suggests that slow charge-transfer processes could represent a major efficiency-limiting parameter in organic solar cells.