Morphology Control Strategies for Efficient Charge Transport versus Injection in Solution-Processed Organic Electronic Devices

<b>ABSTRACT BODY: </b><br/>Organic electronic devices have attracted much attention owing to their advantages such as solution processable, low cost, superior absorption coefficient, flexibility, and so on. By developing of the non-fullerene acceptors (NFAs), organic photovoltaics (OPVs) achieved high power conversion efficiency (PCE) over 19% and organic photodetectors (OPDs) beyond the detectivity of 10¹⁴ Jones. These desirable results are thanks to the various morphology control strategies of organic semiconductor materials, and novel thin film formation process using their. In this study, we suggest the morphology control strategies in terms of materials engineering and thin film lamination process. Representative methods of controlling the morphology of photoactive materials include additive engineering (morphology regulator), and ternary strategies such as introducing the guest components, those enable efficient charge dynamics by controlling molecular orientation. The morphology of the photoactive material which composed of polymer donor PM6 and non-fused ring electron acceptors (NFREAs) TPDC-4F controlled by additive engineering which induce efficient vertical phase distributions of the donor and acceptor components through volatilization process of the high boiling point of additive. Accordingly, we successfully fabricated efficient OPDs (Detecitivty of 1.27 × 10¹³ Jones) with suppressed dark current (3.55 × 10⁻⁹ A cm⁻²) [1]. Moreover, the ternary strategy introducing the high LUMO level guest acceptor (EH-IDTBR) with PM6:BTP-4F-12 binary blend, can block the injected charge from external efficiently and robust transfer the photo-genetrated charge carrier, is promising method for morpholgy regulation. The devices with ternary strategy based on optimal ratio of EH-IDTBR showed advanced OPV (PCE of 16.20%), and OPD (Detectivity of 1.33 × 10¹³ Jones) performances [2]. In addition, morphology also can be adjusted by thin film lamination process. To achieve a desirable thin film surface morphology with a well-distributed donor (PM6) and acceptor (BTP-4F-12) phase in the vertical structure, we developed a vacuum-free (VF) lamination process, in which the blend films with various thicknesses using the adhesion-optimized PUA mediators are transferred onto the target substrates without the vacuum process. Consequently, the VF-laminated devices achieved improved OPV (PCE of 15.97%) and OPD (D* of 3.61×10¹³ Jones) performances. Additionally, the device prepared using the VF-lamination exhibited improved internal resistance, as well as photoresponse property, as observed by optical, electrical, and morphological analyses [3, 4].<br/><br/>[1] M. S. Kim, W. Jang, B. G. Kim, D. H. Wang, Adv. Optical. Mater, 2023, 11, 2202525<br/>[2] M. S. Kim, W. Jang, B. G. Kim, D. H. Wang, J. Mater. Chem. C, 2023,11, 8776-8783.<br/>[3] M. S. Kim, W. Jang, T-Q. Nguyen, D. H. Wang, Adv. Funct. Mater, 2021, 31, 2103705.<br/>[4] M. S. Kim. J. Lim, W. Jang, D. H. Wang, Carbon Energy (Accepted).