Competition between diagonal and off-diagonal coupling gives rise to charge-transfer states in polymeric solar cells

• Main Authors: Yao, Yao, Zhou, Nengji, Prior, Javier, Zhao, Yang
• Other Authors: School of Materials Science & Engineering
• Format: Article
• Language: English
• Published: 2015
• Online Access: https://hdl.handle.net/10356/79252; http://hdl.handle.net/10220/38800
• Institution: Nanyang Technological University

It has long been a puzzle on what drives charge separation in artificial polymeric solar cells as a consensus has yet to emerge among rivaling theories based upon electronic localization and delocalization pictures. Here we propose an alternative using the two-bath spin-boson model with simultaneous diagonal and off-diagonal coupling: the critical phase, which is born out of the competition of the two coupling types, and is neither localized nor delocalized. The decoherence-free feature of the critical phase also helps explain sustained coherence of the charge-transfer state. Exploiting Hamiltonian symmetries in an enhanced algorithm of density-matrix renormalization group, we map out boundaries of the critical phase to a precision previously unattainable, and determine the bath spectral densities inducive to the existence of the charge-transfer state.