Organic Homojunction Diodes with a High Built-in Potential: Interpretation of the Current-Voltage Characteristics by a Generalized Einstein Relation

Abstract

We realize p- and n-type doping of the organic semiconductor zinc-phthalocyanine using a novel strong organic donor. This allows us to demonstrate the first stable and reproducible organic p-n homojunctions. The diodes show very high built-in potentials, attractive, e.g., for organic solar cells. However, the diode characteristics cannot be described by the standard Shockley theory of the p-n junction since the ideality factor strongly increases with decreasing temperature. We show that this behavior can be explained by deviations from the Einstein relation for disordered materials.

Organic Zener Diodes: Tunneling across the Gap in Organic Semiconductor Materials

“…The breakthrough properties of such devices have only been rarely investigated, see, for example, ref 15. The advantage of the pin-diode concept 16 is that the geometry and the potentials within the semiconductor layers can be controlled very precisely, thus allowing the study of the tunneling effects, which sensitively depend on minute variations of these parameters, in a very controlled manner. Thus, the tunneling current is independently tunable by two parameters: the thickness of the intrinsic interlayer (IIL) and the doping concentration of the electron and hole transport layers (ETL/ HTL).…”

pn-control and pn-homojunction formation of metal-free phthalocyanine by doping

“…13 For our next study, we chose metal-free phthalocyanine (H 2 Pc) which is regarded as being p-type, with no reports of it being n-type. A few exceptions are n-type metal phthalocyanine doped with complexes having central metals like ruthenium, 10,14 although there have been intensive studies on doping 15,16 such as F 4 -TCNQ acting as typical p-type dopants. 17 In this study, we used molybdenum oxide (MoO 3 ) 12,13,18,19 and cesium carbonate (Cs 2 CO 3 ) 20,21 as acceptor and donor dopants, respectively.…”

Bandgap Science for Organic Solar Cells

“…These results strongly suggest that, in principle, almost all single organic semiconductors can be controlled to both n-type and p-type by doping alone, similar to the case of inorganic semiconductors. For the cases of C 60 , H 2 Pc, ZnPc, pentacene, and CBP, pn-homojunctions were formed [34,36,38,44,46]. …”

“…[32,33] were found. In terms of donors that are relatively stable in air, Harada et al found a Ru-complex and applied it to fabricate pn-homojunctions in zinc phthalocyanine [34,35] and pentacene [36]. Recently, compounds of alkaline metals, such as Cs 2 CO 3 [37,38], and Co-complexes [39] acting as donor dopants have been identified.…”