Rational design and characterization of high-efficiency planar A–π–D–π–A type electron donors in small molecule organic solar cells: A quantum chemical approach

• A series of A–π–D–π–A type donors with different donor core for OSC were designed.
• The relationship between donor properties and device performance is explored by DFT.
• An In-depth quantum chemical investigation on the affecting factors on Jsc.
• The efficiency of new donor 4 may surpass the reported donor DR3TBDT.

Taking the reported donor DR3TBDT as reference, a series of A–π–D–π–A type donor molecules involving different planar donor cores were designed and investigated by using density functional theory (DFT)/time-dependent DFT methods. Preliminary calculations on geometries, energy levels and spectrum properties show that four of the designed molecules (4, 5, 12 and 13) could become potential donor replacements of DR3TBDT due to their good planarity, larger light harvesting efficiencies and similar exciton migration capability. Additionally, several factors influencing on short-circuit current density (Jsc) were analyzed by in-depth quantum chemical investigations on the transition density matrix, charge transfer indexes, exciton binding energy and Gibbs free energy loss in charge dissociation process. Comparative analyses demonstrate that 4 with indaceno[1,2-b:5,6-b′]dithiophene donor core has more significant electron transfer character and favorable exciton dissociation capability for enhancing the Jsc, and would be potentially promising donor material in organic solar cells.

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