Correction of the calculation method of CT state energy in ITIC and Y6 acceptor systems

Abstract

The charge transfer (CT) state at the donor (D)/acceptor (A) interface in organic solar cell (OSC) is the core of exciton dissociation and geminate recombination processes, which are affected by geometries and electron transition. Recently, the CT mechanism developed by fullerenes has produced some unsuitable phenomena in the application of high performance NFA materials, due to the transformation of the highly (three dimensional) symmetric structure to a linear structure. In order to improve the calculation accuracy and custom-matched calculation models for NFA, two benzo[1,2-b:4,5-b′]difuran (BDF) polymers (P-FT)/3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (m-ITIC) and P-FT/2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl) bis (methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (Y6) were selected as the research objects, the four levels with gradient variation were constructed, including identification methods (CDD or NTO), range-separated hybrid (RSH) functionals, polarizable continuum models (PCM) and related ω parameter. The results show that RSH functional is the dominant factor affecting CT state. The ωB97XD functional should be selected without distinguishing CT state types. However, when considering the types and high-energy of CT states, it should be noted that there is a strong system dependence. In addition, if a solvent model needs to be added, solvent optimization should be performed on the ω parameter. This work aims to define uniform ECT calculation models and standards to improve accuracy and provide suitable target selection for relevant research.