Photoconductive response in organic charge transfer interfaces with high quantum efficiency

Abstract

Organic semiconductors have unique optical, mechanical and electronic properties that can be combined with customized chemical functionality. In the crystalline form, determinant features for electronic applications, such as molecular purity, the charge mobility or the exciton diffusion length, reveal a superior improved performance when compared with materials in a more disordered form. However, the use of organic single crystals in devices is still limited to a few applications, such as field-effect transistors. Here we report the first example of photoconductive behaviour of single-crystal charge-transfer interfaces. The system composed of rubrene and 7,7,8,8-tetracyanoquinodimethane presents a responsivity reaching 1 A W À 1 , corresponding to an external quantum efficiency of nearly 100%. This result opens the possibility of using organic single-crystal interfaces in photonic applications.

Effect of Molecular Stacking on Exciton Diffusion in Crystalline Organic Semiconductors

“…However, for all three PDI derivatives the interfaces yield a R □ three orders of magnitude below resistivity values of rubrene SC alone, on the order of 1-40 GΩ/□. This same trend is observed in other SC interfaces, such as TTF/TCNQ, TMTSF/TCNQ and rubrene/TCNQ, where all interfaces had considerably lower resistivity than any of its isolated materials 33,35,43 . Such effect likely comes from the charge-transfer between rubrene and PDIB, due to the formation of an induced dipole layer at the interface and differences in R □ in the three different interfaces can be related with small changes in the LUMO levels of the PDIBs.…”

“…This was achieved by using charge-transfer interfaces of single-crystals of rubrene and butyl-perylenediimides derivatives (PDIBs) whose structure is varied by chemical design. These crystalline heterojunctions combine high charge-separation and quantum yield efficiencies with the high mobility observed in SCs 33,34 . Assembly by the lamination technique ensures the chemical integrity of the interfaces 33, 35 and, in favorable cases, excitons formed at both donor and acceptor materials can be both harvested 36 .…”

Ultrasensitive organic phototransistors with multispectral response based on thin-film/single-crystal bilayer structures

“…12,15 The selected rubrene SCs with length(L)/width(W) ratio >1 and thickness t < 500 nm were carefully laminated on top of the PC 61 the negative effect of contact resistance on charge-extraction, since R T ¼ R ch þ R c ¼ R s ðL=WÞ þ R c , where R T and R s are the total and sheet resistances, respectively. The crystals completely adhere to the surface of the film, guaranteeing the formation of a nanoscale interface [Figs.…”

Freezing-in orientational disorder induces crossover from thermally-activated to temperature-independent transport in organic semiconductors

“…Examples include metal-insulator transitions, neutral-ionic transitions, Peierls transitions and transitions to a ferroelectric state [3][4][5][6][7][8][9][10][11][12][13] . Historically, these complexes were of interest due to the prediction of room temperature superconductivity or metallic conductivity 14 ; more recently, they have proven to be an excellent medium for the study of novel application-oriented properties such as photoconductivity, tunable semiconductivity, ferroelectricity, magnetoresistance and field emission 3,4,[15][16][17][18][19][20][21][22][23][24][25][26] . Such properties are highly coupled to the crystalline structure of these molecular solids.…”