Charge-transfer state dynamics in all-polymer solar cells: formation, dissociation and decoherence

Abstract

All-polymer solar cells gained substantial achievements in recent years, offering numerous unsettled subjects for mechanical researchers. Based on the Su-Schrieffer-Heeger model, we then simulate the ultrafast dynamics of charge-transfer (CT) state considering a molecular electrostatic potential drop at the interface between two polymer chains, which are respectively regarded as donor and acceptor in all-polymer solar cells. The formation of a stable CT state is found to be sensitive to the distance between two oppositely charged polarons and the relevant critical electrostatic potential is thus quantified. In order to get insight into the dependence of dissociation of CT state on the width of interfacial layer, two quantities are calculated: One is the Coulomb capture radius between two polarons and the other is the quantum trace distance which serves as the fingerprint of the quantum coherence between them. The dissociation of CT state is found to take place within an ultrafast timescale for an optimum interfacial width. The classical spatial distance and the quantum trace distance manifest converging trend suggesting a decoherence scenario for the charge separation in all-polymer solar cells.

Unified dynamic approach for simulating quantum tunneling and thermionic emission at metal/organic interface

“…As well known, interfaces are essential for organic semiconductors in any way. In our previous work, we have discussed an optimum width of donor/acceptor (D/A) interface for the dissociation of the charge-transfer (CT) state [45]. In the practical fabrication of devices, the insertion of a buffer layer between the metallic electrode and the organic layer can effectively facilitate the injection of charge [56][57][58][59] and Hou's group has obtained an optimal buffer layer width of several nanometers based on the model calculations and the experimental investigations [56].…”

“…We notice that, the total increase of entropy is roughly by 3%, not significant compared with our expectation as we expected that following more charges are injected the entropy would largely increases making the quantumness quickly lost. In our previous work, we have also present a coherent scenario of the dissociation of the CT state at the D/A interfaces in the organic photovoltaics [45].…”

Surface hopping simulations on charge separation in an organic donor–acceptor system

“…Previous theoretical work had to adopt very simple models where the electronic structure calculations generally remained below the Hartree-Fock approximation. [13][14][15][16][17] This is because conducting high-level quantum dynamical simulations on charge separation processes is a very challenge task because of the aggregate system size that should be able to accommodate fully separated electrons and holes. In such simple models, some key factors for charge separation such as electron-electron interactions and excitedstate electronic structures have to be neglected or greatly simplified.…”

Charge transfer via deep hole in the J51/N2200 blend

“…Charge transfer (CT) process is one of the key fundamental steps in many molecular optoelectronic materials, ranging from organic solar cells (OSCs) [1][2][3][4][5][6][7][8][9][10] to DNA-based nanoelectronics [11][12][13][14] .…”