Heterojunctions, Diodes

Poly(acetylene) probably comprises one of the most studied CPs for PV, heterojunction, rectification/Schottky barrier and related applications [959-961, 963-969, 971-976, 978]. One of the reasons for this is of course P(Ac) s lower bandgap, ca. 1.5 eV, which more closely matches the solar spectrum than, say, P(Py) (ca. 2.2 eV). 

Hoshino et al. [980] noted that the quality of p-n-heterojunctions formed by depositing CPs such as poly(3-Me-thiophene) and poly(pyrrole) on -Si wafers could be greatly improved by cathodic treatment , i.e. electrochemical reduction, of the CP. Fig. 23-6 shows junction profiles and typical dark I-V characteristics of such heterojunctions before and after such cathodic treatment. 

Other CPs studied in PV cells include the poly(p-pyridyl vinylene)/poly(3-alkyl-thiophene) combination studied by Tada et al. [981], which was found to be superior to a poly(3-alkyl-thiophene)-only single-layer PV cell. 

The characteristics of Schottky barriers between P(Ac) and various low work function metals under white light illumination are summarized in Table 23-1 [961-971]. Conversion efficiencies are however low maximum efficiencies are only ca. 0.3 % to 1.1 %. Table 23-3 summarizes junction parameters for Schottky barriers and heterojunctions based on interfacing P(Ac) to inorganic semiconductors [961, 972-976, 982]. These inorganic semiconductor/P(Ac) cells were found to have higher conversion efficiencies, ca. 6.2%, as compared to Au/GaAs cells, ca. 4.6%. 

Characteristics of Schottky barriers between P(Ac) and various low work function metals under white light illumination at 300°K. After References [961-976, 982]. 

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NS Sariciftci, D Braun, C Zhang, VI Srdanov, AJ Heeger, and F Wudl, Semiconducting polymer-buckminsterfullerene heterojunctions diodes, photodiodes and photovoltaic cells, Appl. Phys. Lett., 62 585-587, 1993. 

Potje-Kamloth, K. (2001) Conducting polymer based Schottky and heterojunctions diodes and their sensor application. In Nalwa, H.S. (Ed.) Handbook of Surfaces and Interfaces of Materials, Vol. 5. Academic Press, p. 445—494. 

A two colour infrared detector is described in US-A-5300777 which for each detector element comprises a heterojunction diode and a metal-insulator-semiconductor device. 

Fig. 5.7. Typical I/V characteristics of a bulk heterojunction diode. The schematic band diagrams for the three different diode regimes axe depicted in the figure according to the applied voltage...

The hole mobility /u-h in OCiCio-PPV is 5 x 10-11 m2/V s. The electron mobility /xe in PCBM is 2 x 10-7 m2/V s. However, the transport of separate charge carriers in an interpenetrating network may be different than the transport in the individual compounds. In Ref. [65] the transport and injection of charge carriers in OCiCio-PPV PCBM bulk-heterojunction diodes are investigated. 

Treboux G, Lapstun P, Silverbrook K (1999) An intrinsic carbon nanotube heterojunction diode. J. Phys. Chem. B 103 1871-1875... 

Levy, B., W. Liu and S.E. Gilbert (1997). Directed photocurrents in nanostructured Ti02/Sn02 heterojunction diodes. Journal of Physical Chemistry B, 101(10), 1810-1816. 

Also organic compound like metal phthalocya-nines [xxvi] and electronic conducting polymers [xxvii] are used as gas-sensitive layers in resistive sensors, POSFETs (polymer oxide silicon field-effect transistors), heterojunction diodes (e.g., polyrrole on... 

There is great interest in ta-C as for electronic devices. Already a heterojunction diode has been fabricated from ta-C [47]. 

Sariciftci NS, Braun D, Zhang C, Srdanov VI, Heeger AJ, Stucky G, Wudl F (1993) Semiconducting polymer-buckminsterfullerene heterojunctions diodes, photodiodes, and photovoltaic cells. Appl Phys Lett 62 585... 

General Motors Research Laboratories (GMR). Molecular beam epitaxial (MBE) growth of Pbi xEuxSeyTei y lattice-matched to PbTe substrates has been used to fabricate double heterojunction diode lasers, including quantum well, large optical cavity (LOG) devices, the first such TDL structures reported for a lead-salt compound. These Mesa stripe... 

Shen Y, Wan M (1998) Heterojunction diodes of soluble conducting polypyrrole with porous silicon. Synth Metals 98 147-152... 

Potje-Kamloth K (2001) Conducting polymer-based Schottky barrier tmd heterojunction diodes and their sensor application. In Nalwa HS (ed) Handbook of surfaces tmd interfaces of materials, vol 5. Academic, San Diego, CA, pp 445-494... 

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