Switching of Electron and Ion Conductions by Reversible H₂O Sorption in n-Type Organic Semiconductors

Abstract

Polar H 2 O molecules generally act as trapping sites and suppress the electron mobility of n-type organic semiconductors, making chemical design of H 2 O-tolerant and responsive n-type semiconductors an important step toward multifunctional electron−ion coupling devices. The introduction of effective electrostatic interactions between potassium ions (K + ) and carboxylate (−COO − ) anions into the electron-transporting naphthalenediimide πframework enables the design of high-performance H 2 O-tolerant n-type semiconductors with a reversible H 2 O adsorption−desorption ability, where the electron mobility and K + ionic conductivity were coupled with the reversible H 2 O sorption behavior. The reversible H 2 O adsorption into the crystals enhanced the electron mobility from 0.04 to 0.28 cm 2 V −1 s −1 , whereas the K + ionic conductivity decreased from 3.4 × 10 −5 to 4.7 × 10 −7 S cm −1 . Because this reversible electron−ion conducting switch is responsive to H 2 O sorption behavior, it is a strong candidate for H 2 O gating carrier transport systems.

Crystal Lattice Design of H2O-Tolerant n-Type Semiconducting Dianionic Naphthalenediimide Derivatives

“…, respectively, at 298 K. 56 The PXRD patterns of both hydrated and dehydrated thin films suggested the formation of highly crystalline states during the H 2 O adsorption−desorption cycle of the 3•(H 2 O) n thin films. 56 From the TAS spectra, the Σμ values of the 3• (H 2 O) 0 , 3•(H 2 O) 2.5 , and 3•(H 2 O) 4.0 thin films were 0.048 ± 0.006, 0.28 ± 0.01, and 0.13 ± 0.01 cm 2 V −1 s −1 , respectively.…”

“…Interestingly, hydrated crystals of (K + ) 2 (PCNDI 2− )•(H 2 O) 2.5 exhibited a high electron mobility of 0.28 cm 2 V −1 s −1 in the presence of H 2 O molecules, whereas the electron mobility decreased to 0.04 cm 2 V −1 s −1 for the dehydrated state of (K + ) 2 (PCNDI 2− )•(H 2 O) 0 . 56 An interesting H 2 O response was observed in the design of the electrostatic crystal lattice of the n-type semiconducting materials. Strongly binding electrostatic intermolecular interactions can generate a rigid crystal lattice, wherein even n-type semiconducting materials exhibit H 2 O-tolerant semiconducting behavior.…”

“…Single-crystal X-ray structural analysis of fully hydrated 3• (H 2 O) 4.0 at 100 K has been conducted in a previous study. 56 Alternate 2D layers of the π cores of NDI and the (K + ) 2 ••• (H 2 O) 4 network were elongated along the a axis, which were connected to each other by the electrostatic K + ••• − OOC− interactions. The two terminal −COO − groups of PCNDI 2− were coordinated to the K + cation with d K−O = 2.716(6) and 2.738( 6) Å (Table S2).…”

Electrostatic versus van der Waals Interactions in an n-Type Semiconducting Dianionic Naphthalenediimide Derivative with CnH2n+1NH3+ (n = 1–16)

“…Crystals of (Na + ) 2 ( BSNDI 2– ) showed an electron mobility of 0.22 V cm –2 s –1 at 298 K and extremely high thermal stability up to 850 K . Instead of rigid benzene sulfonate units, two flexible propionate (−C 2 H 5 COO – ) groups were introduced into a NDI π-core to form dianionic bis­(propionate)-naphthalenediimide (PCNDI 2– ). , Single-crystal X-ray structural analyses were performed for the hydrated (M + ) 2 ( PCNDI 2– )•(H 2 O) n with M + = Na + , K + , Rb + , and Cs + and revealed not just H 2 O-tolerant but H 2 O-responsive n-type semiconducting behavior coupled with the reversible H 2 O adsorption–desorption behavior and electron mobility switching. The softness and hardness of the cation–anion crystal lattices were systematically modulated by replacing the alkali metal ions, and the electron transport property was dominated by the crystal lattice. , In the case of BSNDI 2– salts, inorganic M + cations, such as Na + , K + , and NH 4 + , were conventionally replaced with organic cations such as CH 3 NH 3 + , C 2 H 5 NH 3 + , (C 2 H 5 ) 2 NH 2 + , and (C 2 H 5 ) 3 NH + .…”

“…Crystals of (Na + ) 2 (BSNDI 2− ) showed an electron mobility of 0.22 V cm −2 s −1 at 298 K and extremely high thermal stability up to 850 K. 68 Instead of rigid benzene sulfonate units, two flexible propionate (−C 2 H 5 COO − ) groups were introduced into a NDI π-core to form dianionic bis(propionate)-naphthalenediimide (PCNDI 2− ). 69,70 Singlecrystal X-ray structural analyses were performed for the hydrated (M + ) 2 (PCNDI + , and (C 2 H 5 ) 3 NH + . This significantly changed the molecular assembly structures and showed a dimensional crossover from 2D, 1D, to 0D electronic structures.…”