Exploring what prompts ITIC to become a superior acceptor in organic solar cell by combining molecular dynamics simulation with quantum chemistry calculation

Abstract

The interface characteristic is a crucial factor determining the power conversion efficiency of organic solar cells (OSCs). In this work, our aim is to conduct a comparative study on the interface characteristics between the very famous non-fullerene acceptor, ITIC, and a fullerene acceptor, PC71BM by combining molecular dynamics simulations with density functional theory. Based on some typical interface models of the acceptor ITIC or PC71BM and the donor PBDB-T selected from MD simulation, besides the evaluation of charge separation/recombination rates, the relative positions of Frenkel exciton (FE) states and the charge transfer states along with their oscillator strengths are also employed to estimate the charge separation abilities. The results show that, when compared with those for the PBDB-T/PC71BM interface, the CT states are more easily formed for the PBDB-T/ITIC interface by either the electron transfer from the FE state or direct excitation, indicating the better charge separation ability of the former. Moreover, the estimation of the charge separation efficiency manifests that although these two types of interfaces have similar charge recombination rates, the PBDB-T/ITIC interface possesses the larger charge separation rates than those of the PBDB-T/PC71BM interface. Therefore, the better match between PBDB-T and ITIC together with a larger charge separation efficiency at the interface are considered to be the reasons for the prominent performance of ITIC in OSCs.

In situ Measuring Film-Depth-Dependent Light Absorption Spectra for Organic Photovoltaics

“…The absorption spectrum of blend film is from 500 to 800 nm. As a classic system, lots of work were devoted to performance optimization and mechanism research of PBDB-T/ITIC devices Zhao W. C. et al, 2016;Pan et al, 2017;An et al, 2018;Bi et al, 2018;Liang et al, 2018). Here, we mainly study the film-depth-dependent optical and electrical properties by the in situ instrument.…”

Nanostructure of organic semiconductor thin films: Molecular dynamics modeling with solvent evaporation

“…These methods can provide quantitative, statistical information on structural parameters: The former of molecular order such as π -stacking distances and lamellar stacking distances in both neat films and blend films, and the latter of mesoscale order such as domain sizes in blend films. To interpret data from these measurements, molecular dynamics (MD) simulations can prove helpful by providing * jewa@dtu.dk a more qualitative insight into the short-range structural parameters, and, in combination with quantum chemical calculations, elucidating different aspects of the structure-property relationships [17,18].…”

Spin‐Dependent Electron–Hole Recombination and Dissociation in Nonfullerene Acceptor ITIC‐Based Organic Photovoltaic Systems

“…Among many NFAs, 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′] dithiophene (ITIC), a group member of indacenodithiophene‐based small molecular acceptors (IDT‐based SMA), is one of the most representatives exhibiting desirable PCE in conjunction with some electron D such as poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]‐dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and poly[(2,6‐(4,8‐Bis(3‐((2‐ethylhexyl)oxy)‐phenyl)‐benzo[1,2‐b:4,5‐b′]‐dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBPD‐Th) . The schematic drawings of their molecular structures are given in Figure S1, Supporting Information.…”

“…The ITIC molecule comprises linearly fused acceptor–donor–acceptor (A–D–A) aromatic backbones with two side and two end chains . Its prominent performance has been proposed due to the easy formation and better charge separation ability of CT states with PBDB‐T based on molecular dynamic simulations (MDS) . In spite of its electronic structure, chemical property, and charge transport behavior, spin‐dependent energy states associated with the photo‐induced electron–hole recombination and dissociation at intra‐ and intermolecular states remain an open question.…”