Systematic Investigation of Core and Endcap Selection on the Development of Functional π-Conjugated Materials

Abstract

We investigate the optoelectronic properties of four new πconjugated materials, which feature either a 3,4-ethylenedioxythiophene (EDOT) or an EDOT-flanked benzothiadiazole aryl core with two N-annulated perylene diimide (NPDI) or theobromine endcaps. Endcap selection was an important factor for the preferred molecular geometry, where the use of NPDI endcaps induced a dragonfly-type conformation and the use of theobromine endcaps promoted a corkscrew-like conformation. Electrochemically, the choice of aryl πconjugated core was found to have a strong influence on the molecule's highest occupied molecular orbital (HOMO) energy level, while the choice of endcap had a more profound effect on the lowest unoccupied molecular orbital (LUMO) energy level. Although the optical absorption profiles were generally dominated by endcap contributions, using the larger EDOT-flanked benzothiadiazole aryl core was found to decrease the optical energy band gap. Proof-of-concept organic photovoltaic (OPV) devices, using a PM6:Y6 bulk heterojunction (BHJ) photoactive layer, were fabricated using the four new π-conjugated materials as the cathode interlayer (CIL). The molecules featuring the EDOT aryl core (A and B) enabled OPV device power conversion efficiencies (PCEs) by around 12%, comparable to control devices using PDINN as the CIL, while those featuring the EDOT-flanked benzothiadiazole aryl core (C and D) obtained PCEs of 10.5%. The observed differences in OPV device performance were attributed to superior solubility and subsequent CIL film formation in the case of A and B, compared to C and D, which, in turn, led to improved contact between the Ag top electrode and the BHJ photoactive layer.

Mechanochemical synthesis of biphenyl-derived organic fluorescent materials via solvent-free and ligand-free oxidative homocoupling reactions

“…[1][2][3][4] The development of efficient and facile synthetic methods for dimerized functional conjugated materials is vital to their applications. 5 Conventional solution approaches have been widely reported for synthesizing biphenyl-based conjugated materials. 6,7 Recently, solid-state mechanochemical synthesis using ball milling has attracted increasing attention as an alternative and efficient synthetic approach.…”

Ternary organic solar cells with a selenophene-containing donor guest achieve a high efficiency of 18.41%

“…[13][14][15][16][17][18][19][20][21][22] Combining the unique advantages of light weight, large-area fabrication, and flexibility, BHJ-OSCs show great commercialization prospects. [23][24][25][26][27][28][29] To date, the traditional binary BHJ-OSCs consisting of a polymer donor and a nonfullerene acceptor (NFA) in the active layer have demonstrated great success; however, the shortcomings, such as inferior light capturing, higher energy loss (E loss ), lower open-circuit voltage (V oc ), and fill factor (FF), should not be neglected. [30][31][32][33] Therefore, great efforts have been devoted in finding that introducing a third component into a binary host system is an effective strategy to resolve the critical problems mentioned above.…”

“…13–22 Combining the unique advantages of light weight, large-area fabrication, and flexibility, BHJ-OSCs show great commercialization prospects. 23–29…”

Polyconjugated Materials for Printed (Opto)Electronics: Introducing Sustainability

“…First and foremost, the flexibility of organic chemistry allows the design of a vast array of materials sharing the same cheap and available components (C, H, N, S, O, P) and possessing optoelectronic properties tailored to suit a specific application. Organic field effect transistors (OFETs), 1 electro-optic modulators, [10][11][12] organic solar cells (OSCs), 3,7,13,14 organic lightemitting devices (OLEDs), 15,16 sensors of many different kinds, [17][18][19][20] rechargeable batteries and supercapacitors, 21 organic light-emitting transistors (OLETs), 22,23 light-emitting electrochemical cells (LEECs), 24 and thermoelectric generators (TEGs) 20,25,26 are just a few examples of the vast array of technologies benefiting from the unique properties of organic semiconductors. Aside from optoelectronic features, organic materials are also advantageous in terms of compatibility with low-cost solution-processing techniques (including printing) and mechanical flexibility.…”