Carbon Nanodots as Electron Transport Materials in Organic Light Emitting Diodes and Solar Cells

• Published in: Nanomaterials (Basel, Switzerland) Switzerland), 2022-12, Vol.13 (1), p.169
• Main Authors: Georgiopoulou, Zoi, Verykios, Apostolis, Ladomenou, Kalliopi, Maskanaki, Katerina, Chatzigiannakis, Georgios, Armadorou, Konstantina-Kalliopi, Palilis, Leonidas C, Chroneos, Alexander, Evangelou, Evangelos K, Gardelis, Spiros, Yusoff, Abd Rashid Bin Mohd, Coutsolelos, Athanassios G, Aidinis, Konstantinos, Vasilopoulou, Maria, Soultati, Anastasia
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Aluminum; Atomic force microscopy; Carbon; Carbon dots; carbon nanodots; Cathodes; Charge injection; Copolymers; Electric properties; Electrical measurement; Electrodes; Electron transport; electron transport materials; Energy conversion efficiency; Fluorescence; Fourier transform infrared spectroscopy; Fourier transforms; Glass substrates; Injection; Interlayers; Market entry; Mechanical properties; Nanoparticles; Nitrogen; Optoelectronics; Organic light emitting diodes; organic solar cells; Perovskites; Photovoltaic cells; Quantum dots; Solar cells; Spectrum analysis; Structure; surface functionalization; Thiadiazoles; Voltammetry; Zinc oxides
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano13010169

Charge injection and transport interlayers play a crucial role in many classes of optoelectronics, including organic and perovskite ones. Here, we demonstrate the beneficial role of carbon nanodots, both pristine and nitrogen-functionalized, as electron transport materials in organic light emitting diodes (OLEDs) and organic solar cells (OSCs). Pristine (referred to as C-dots) and nitrogen-functionalized (referred to as NC-dots) carbon dots are systematically studied regarding their properties by using cyclic voltammetry, Fourier-transform infrared (FTIR) and UV-Vis absorption spectroscopy in order to reveal their energetic alignment and possible interaction with the organic semiconductor's emissive layer. Atomic force microscopy unravels the ultra-thin nature of the interlayers. They are next applied as interlayers between an Al metal cathode and a conventional green-yellow copolymer-in particular, (poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)], F8BT)-used as an emissive layer in fluorescent OLEDs. Electrical measurements indicate that both the C-dot- and NC-dot-based OLED devices present significant improvements in their current and luminescent characteristics, mainly due to a decrease in electron injection barrier. Both C-dots and NC-dots are also used as cathode interfacial layers in OSCs with an inverted architecture. An increase of nearly 10% in power conversion efficiency (PCE) for the devices using the C-dots and NC-dots compared to the reference one is achieved. The application of low-cost solution-processed materials in OLEDs and OSCs may contribute to their wide implementation in large-area applications.