Kinetic model for photoluminescence quenching by selective excitation of D/A blends: implications for charge separation in fullerene and non-fullerene organic solar cells

Abstract

<p>Our findings demonstrate the importance of kinetic factors in determining the overall charge separation efficiency in D/A systems.</p>

A Comparison of Charge Carrier Dynamics in Organic and Perovskite Solar Cells

“…[84][85][86][87] Organic donor:acceptor blends show strongly quenched emission relative to neat materials, attributed to exciton dissociation and subsequent nonradiative charge recombination at the donor/acceptor interface; this PL quenching is widely used as an assay of efficient exciton separation in organic blends. [88][89][90][91] By contrast, in neat perovskite films, PL emission comes from the radiative recombination of free charge carriers, with the main competing pathway being charge localization into nonradiative trap states. [41,92] Such nonradiative charge trapping is most dominant at low light fluxes, but becomes at least partially suppressed at high light intensities (e.g., 1 sun), attributed to trap filling.…”

Kinetic Modeling of the Electric Field Dependent Exciton Quenching at the Donor–Acceptor Interface

“…Those findings motivated us to extend the previous model in ref to include the influence of the electric field on the kinetics of charge separation at the D/A interface. We also refined the model by considering the effects of energetic, positional, and electronic coupling disorders on those processes.…”

“…Note from eq that if the donor is not efficient to dissociate the excitons, then [ S 1,A ′] ≈ [ S 1,A ] and Q A ≈ 0. The solution of the model’s differential equations in steady-state approximation gives the quenching efficiency for the acceptor and the donor excitations (further details can be found in ref ): and where the k ’s in eqs and are the rates that characterizes all possible electronic transitions after the formation of the singlet state either in the acceptor (eq ) or in the donor (eq ). In Table , we detail all those rates in eqs and with the corresponding electronic transitions and the frontier molecular orbitals involved (HOMO, highest occupied molecular orbital, and LUMO, lowest unoccupied molecular orbitals).…”

“…When Δ G < 0, the process is thermodynamically favorable. All the driving forces involved in the hole and electron transitions for the zero electric field are presented in Table . The reorganization energies in this table are assumed independent of the F , as demonstrated in ref .…”

“…Other kinetic models were proposed to describe the dynamics of the exciton dissociation at the D/A heterojunction. In ref , a model for the charge separation processes in those systems was proposed. In this theory, the formation of a singlet exciton (S 1 ) in one of the BHJ phases was considered as a primary event.…”