Simple charge transport model for efficient search of high-mobility organic semiconductor crystals

Abstract

High charge mobility in active layers of organic electronic devices is often necessary for their efficient operation. As a result, search for high-mobility materials among the plethora of synthesizable organic semiconductors is of paramount importance for organic electronics. However, a model for rapid but reliable prediction of charge mobility in various organic semiconductors is still lacking. To solve this issue, we propose a simple analytical model that considers the most essential factors governing the charge transport in these materials: intermolecular electronic coupling, charge delocalization, electron-phonon interaction, and static and dynamic disorder. The suggested model efficiently predicts charge mobility for organic semiconductors of various chemical structures and sizes, and significantly outperforms another approach usually used for screening of organic semiconductors, -Marcus model, -which overlooks highmobility materials possessing small conjugated cores. We thus anticipate that the suggested model is an efficient tool for the search of the high-mobility organic semiconductors, and its possible integration with crystal structure prediction can boost the development of organic electronics.

Tuning of Molecular Electrostatic Potential Enables Efficient Charge Transport in Crystalline Azaacenes: A Computational Study

“…As a result, charge transport proceeds via an inefficient hopping mechanism; the hopping rate increases with J and decreases with λ [5][6][7]. Nevertheless, if J is sufficiently large, significant intermolecular charge delocalization, resulting in efficient bandlike charge transport, can take place [5,8,9]. Thus, increasing J and decreasing λ is important for the improvement of charge mobility in OSs.…”

“…It was noticed that the largest J is generally observed for face-to-face arrangements typical of the π-stacking packing motif [ 13 , 19 ]. For instance, in the OSs with record μ , e.g., crystalline rubrene (hole transport) [ 20 ] and F 2 -TCNQ (electron transport) [ 21 ], the largest J is observed for the face-to-face orientation of adjacent molecules and amounts to ~70–110 meV, which is significantly larger than the energy of thermal fluctuations (25 meV at room temperature) [ 8 ]. For this reason, crystalline OSs with π-stacking have attracted particular attention in recent decades.…”

Organic nanoelectronics inside us: charge transport and localization in RNA could orchestrate ribosome operation

“…All the λ values are large and exceed 300 meV (cf. λ ~ 100 meV for organic semiconductors with efficient charge transport, e.g., rubrene and DNTT [42,43]); the λch values are comparable to those of λdis. Importantly, the λ value for guanine-the most probable site for hole localization-is more than 20 times larger than the energy of thermal fluctuations (25 meV at room temperature).…”

“…For a number of neighboring nucleobase pairs, the calculated transfer integrals exceed 100 meV. These values are quite large, which is beneficial for charge transport: in many organic semiconductors with high charge mobility, all J values are below 100 meV [42,43]. Inset of Fig.…”

“…Also, we intentionally used a rather simple charge transport model based on the Marcus theory, although charge transport in nucleic acids can be more complex and still remains a subject of debates [40]. Possible charge delocalization between the sites that could decrease the effective reorganization energies [51][52][53]43] was neglected. Moreover, the very site energies (ionization potentials of nucleotides) can be dependent on charge delocalization [54] and hence on J. Ionic conductivity, which can be coupled to the electronic charge transport discussed herein [55], is also accounted for simply at the level of counterions added to tRNA.…”