Introducing a Nonvolatile N‐Type Dopant Drastically Improves Electron Transport in Polymer and Small‐Molecule Organic Transistors

• Published in: Advanced functional materials Vol. 29; no. 34
• Main Authors: Panidi, Julianna, Kainth, Jaspreet, Paterson, Alexandra F., Wang, Simeng, Tsetseris, Leonidas, Emwas, Abdul‐Hamid, McLachlan, Martyn A., Heeney, Martin, Anthopoulos, Thomas D.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.08.2019
• Subjects: Charge transport; Contact resistance; Deactivation; Density functional theory; Dopants; Doping; Electron mobility; Electron paramagnetic resonance; Electron transfer; Electron transport; Impact resistance; Malononitrile; Materials science; molecular doping; Naphthalene; n‐type dopant; Organic semiconductors; organic transistor; Photovoltaic cells; Polymers; Semiconductor devices; Semiconductors; Solar cells; Temperature dependence; Threshold voltage; Transistors
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201902784

Molecular doping is a powerful yet challenging technique for enhancing charge transport in organic semiconductors (OSCs). While there is a wealth of research on p‐type dopants, work on their n‐type counterparts is comparatively limited. Here, reported is the previously unexplored n‐dopant (12a,18a)‐5,6,12,12a,13,18,18a,19‐octahydro‐5,6‐dimethyl‐ 13,18[1′,2′]‐benzenobisbenzimidazo [1,2‐b:2′,1′‐d]benzo[i][2.5]benzodiazo‐cine potassium triflate adduct (DMBI‐BDZC) and its application in organic thin‐film transistors (OTFTs). Two different high electron mobility OSCs, namely, the polymer poly[[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐ bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2′‐bithiophene)] and a small‐molecule naphthalene diimides fused with 2‐(1,3‐dithiol‐2‐ylidene)malononitrile groups (NDI‐DTYM2) are used to study the effectiveness of DMBI‐BDZC as a n‐dopant. N‐doping of both semiconductors results in OTFTs with improved electron mobility (up to 1.1 cm2 V−1 s−1), reduced threshold voltage and lower contact resistance. The impact of DMBI‐BDZC incorporation is particularly evident in the temperature dependence of the electron transport, where a significant reduction in the activation energy due to trap deactivation is observed. Electron paramagnetic resonance measurements support the n‐doping activity of DMBI‐BDZC in both semiconductors. This finding is corroborated by density functional theory calculations, which highlights ground‐state electron transfer as the main doping mechanism. The work highlights DMBI‐BDZC as a promising n‐type molecular dopant for OSCs and its application in OTFTs, solar cells, photodetectors, and thermoelectrics. A nonvolatile n‐type molecular dopant (12a,18a)‐5,6,12,12a,13, 18,18a,19‐octahydro‐5,6‐dimethyl‐13,18‐ [1′,2′]‐benzenobisbenzimidazo [1,2‐b:2′,1′‐d]benzo[i][2.5]benzodiazocine potassium triflate adduct is introduced, and its ability to improve the operating characteristics of high electron mobility organic transistors based on a polymer and a small molecule is demonstrated. The doping process is shown to reduce the contact resistance and activation energy while simultaneously increasing the electron mobility in both transistors.