Elsevier

Solid State Communications

Volume 163, June 2013, Pages 23-27
Solid State Communications

Hybrid photodiodes based on 6,13-bis(triisopropylsilylethynyl) pentacene:poly[2-methoxy-5-(2-ethyl) hexoxy-phenylenevinylene]/p-silicon

https://doi.org/10.1016/j.ssc.2013.03.015Get rights and content

Highlights

  • The present work aims to fabricating photodiodes of the configuration p-Si/TIPS:MEH-PPV/Al.

  • The electronic parameters for all investigated p-Si/TIPS:MEH-PPV/Al diodes were calculated.

  • The obtained results for p-Si/(TIPS)10:(MEH-PPV)4/Al showed highly optoelectric response.

Abstract

6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS) and poly[2-methoxy-5-(2-ethyl) hexoxy-phenylenevinylene] (MEH-PPV) blends with different ratios were deposited onto a p-type silicon (p-Si) single crystal wafer using spin coating technique. The dark current–voltage characteristics of the fabricated diodes were studied at room temperature. This study was carried out to predict the best blend composite to obtain a qualified diode for use in potential application. The obtained results suggest that the diode with 10:4 ratio between TIPS and MEH-PPV has the highest values for both the rectification factor (r=1.7×103) and the ratio between shunt resistance, Rsh, and series resistance, Rs, (Rsh/Rs=1.23×104) among the investigated diodes. Accordingly, the capacitance–voltage–frequency and conductance–voltage–frequency measurements were carried out for this diode in the frequency range between 10 kHz and 1 MHz at room temperature. Moreover, the I–V characteristics of such a diode were studied under different illumination intensities (P=20:100mW/cm2). The obtained results show a highly optoelectric response; i.e., the diode can be operated as a heterojunction photodiode.

Introduction

Pentacene, a fused-ring polycyclic aromatic hydrocarbon, is considered as one of the most promising π-conjugated organic materials for use in organic electronics. This can be attributed to its excellent semiconducting behavior, which is comparable to that of hydrogenated amorphous silicon (a-Si:H) [1], [2], [3], [4], [5]. However, pentacene has a relatively low electrical charge mobility due to the fact that it is commonly packed in the form edge-to-face in 2D layers which minimizes the π-overlap between adjacent molecules [6]. In order to overcome this shortcoming, Anthony et al. [7], [8], [9] suggested that the use of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS) is better than that of unsubstituted pentacene to achieve higher electrical mobility by increasing the stacking of π-conjugated molecules in face-to-face stack (π-stacking) which provides more efficient π-orbital overlap. Moreover, TIPS has good solution processability and lower interplanar spacing than unsubstituted pentacene. On the other hand, the recognizable and substantial interest of research workers in poly[2-methoxy-5-(2-ethyl)hexoxy-phenylenevinylene] (MEH-PPV) is attributed to the likelihood of various optoelectronic applications such as organic light emitting diodes (OLED), sensors and organic solar cells [10], [11]. Due to the importance of both TIPS and MEH-PPV in the field of organic semiconductors, the present work aimed to fabricate new diodes based on the blending of TIPS and MEH-PPV with different ratios and deposition on p-Si. Also, the electrical and photoelectrical characterizations for the fabricated TIPS:MEH-PPV/p-Si diodes were studied in order to determine the best diode that would be suitable in potential applications.

Section snippets

Experimental

High purity 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS) and poly[2-methoxy-5-(2-ethyl) hexoxy-phenylenevinylene] (MEH-PPV) were purchased from Sigma-Aldrich and used without further purification. TIPS and MEH-PPV organic materials were dissolved in chlorobenzene and chloroform, respectively. The blends of TIPS and MEH-PPV were prepared for various molar ratios, i.e., TIPS:MEH-PPV; 10:1, 10:2, 10:3 and 10:4. The prepared blends were deposited onto p-type Si substrates via spin coating at

Dark current–voltage characteristics for p-si/TIPS:MEHPPV/Al diodes

Fig. 1 shows forward and reverse bias I–V characteristics for the investigated diodes at room temperature. As seen in Fig. 1, the diodes exhibit quite a large rectification ratio. The calculated rectification ratio (r) values at ±2 V for all the studied diodes are given in Table 1. As seen in Table 1, the value of r increases with the increasing concentration of MEH-PPV and reached 1.7×103 for 0.4 mL of MEH-PPV. Here, it is significant to note that the large values of r can be attributed to

Conclusions

In the present study, TIPS:MEH-PPV/p-Si diodes were fabricated using spin coating technique with different molar ratios of organic layers ( from 10:1 to 10:4). The device parameters (r, ϕB, n, Rs and Rsh) of all the diodes were calculated from dark I–V measurements. The obtained results showed that the diode of the highest concentration of MEH-PPV, with a deposited organic layer blend ratio of 10:4, exhibits the best performance in all the prepared diodes. The electrical characterization of

Acknowledgments

One of the authors (Sh.A. Mansour) is grateful to the Scientific and Technological Research Council of Turkey (Tubitak)—BIDEB for providing him a fellowship to work in Turkey via Research Fellowship Programme for Foreign Citizens.

References (32)

  • A.O. Sevim et al.

    Org. Electron.

    (2009)
  • A. Ltaief et al.

    Synth. Met

    (2004)
  • S. Aydogan et al.

    Polymer (Guildf)

    (2005)
  • M.F. Kotkata et al.

    Thin solid films

    (2010)
  • Sh.A. Mansour et al.

    Solid State Sci.

    (2012)
  • F. Yakuphanoglu

    Sens. Reactors A

    (2008)
  • G.S. Chung et al.

    J. Alloys Compd

    (2010)
  • M. Cakar et al.

    Synth. Met

    (2004)
  • A. Tataroglu et al.

    Vacuum

    (2008)
  • P. Chattopadhyay et al.

    Solid-State Elec.

    (1992)
  • A. Tataroglu et al.

    Microelectronics Eng.

    (2008)
  • A. Salleo et al.

    Appl. Phys. Lett.

    (2002)
  • S.E. Fritz et al.

    J. Am. Chem. Soc.

    (2004)
  • H. Yang et al.

    J. Am.Chem. Soc.

    (2005)
  • R. Ruiz et al.

    Adv. Mater.

    (2005)
  • D.H. Kim et al.

    Adv. Mater.

    (2007)
  • Cited by (12)

    • Design, fabrication and optical characterizations of pyrimidine fused quinolone carboxylate moiety for photodiode applications

      2020, Optik
      Citation Excerpt :

      Recently, organic semiconductors of small molecules, especially π-conjugated structures, have conventional increasing consideration and extensively studied owing to promising characteristics like low-cost, reproducibility, lightweight, transparency, mechanical flexibility, as well as the compatibility for providing with a widespread method, such as thermal evaporation, spray pyrolysis, spin coating, inkjet printing methods [21,22]. Talented applications of organic semiconductor films comprise optoelectronics like organic light-emitting devices, organic lasers, organic light-emitting devices, photovoltaic cells organic field-effect, chemical sensors, and other related applications [23]. These varieties of applications can be attributed to the unique and attractive electrical and optical characteristics of organic structures.

    • Electrical, dielectric characterizations and optoelectronic applications of epitaxially grown Co/n-CuO/p-Si heterojunctions

      2019, Superlattices and Microstructures
      Citation Excerpt :

      Accordingly, at the region of lower frequencies, the total capacitance increases due to the high influence of the interface state because the dipoles can follow the signal of ac field and then the additional capacitance resultant from the interface states is added to total capacitance. While, at high frequencies range, the interface states are nearly small due to the unattainability for the dipoles to rearrange itself and then have a little response to the ac field and consequently, the impact of the interface to the capacitance, compared to the total capacitance is nearly small [30]. Similar behavior was recorded for the G-V (Fig. 5(b)) characteristics due to the same influence of the interface under the influence of frequency at various applied bias.

    • A novel type heterojunction photodiodes formed junctions of Au/LiZnSnO and LiZnSnO/p-Si in series

      2015, Journal of Alloys and Compounds
      Citation Excerpt :

      The obtained n value of the diodes is higher than unity. The high value of n is attributed to the presence of inhomogeneities of the barrier height, the particular distribution of the interface states, series resistance, the image force effect, generation–recombination currents within the space-charge region, wide distribution of low Schottky barrier height patches at metal/semiconductor interface, and tunneling [20–30]. Fig. 7 shows semi-logarithmic I–V characteristics of the photodiodes at 100 mW/cm2 illumination intensity.

    • Rectifying properties of TIPS-pentacene:rhodamine blend organic semiconductor-on-p-silicon diodes

      2014, Synthetic Metals
      Citation Excerpt :

      The growing demand of electronic devices adapted from organic semiconductors made is necessary to understand the existence of organic film formed at metal/p-Si interface by the help of the electrical characteristics analysis [4–26]. Organic compounds with different physical and chemical properties formed at metal/inorganic semiconductor interface were thought to change the electrical parameters of the structure by many researchers [4–26]. Metal/Si, metal/GaAs and metal/InP diodes have been fabricated by forming a range of organic interlayers at metal/Si [4–26].

    View all citing articles on Scopus
    View full text