Hierarchical modeling of electron and hole transport in nanoparticle thin films: From ab initio to Monte Carlo

Nanoparticle solar cells show the promise of enhancing the efficiency of solar cells over the Shockley-Queisser limit due to the quantum-confinement-enhanced charge multiplication process. A fundamental challenge of nanoparticle solar cells, however, is that the same quantum confinement that enhances charge multiplication also tends to localize the carriers and thus hinders charge transport. To create a roadmap for overcoming this challenge, we developed a multi-scale transport modeling scheme that starts with ab initio modeling of individual nanoparticles, continues with extracting a few summary parameters that best characterize the physics of these nanoparticles, such as charging energies and size dependent energy levels, and finally feeds this information into a kinetic Monte Carlo hopping transport framework to simulate electron and hole transport across realistically modeled nanoparticle films and devices. We demonstrate the power of this hierarchical modeling by exploring the carrier mobilities of PbSe nanoparticle films as a function of composition, disorder and temperature, where comparison of our results with experiments is possible.