Elucidation of electrical conductivity of DNA polyion-complexes and the applications for optoelectronic devices

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DNA forms a double helix structure that contains four bases (adenine (A), cytosine (C), guanine (G), and thymine (T). It is basically an abundance of πelectrons. Because a regular sequence of the four bases in DNA can be assumed to be a conducting wire, we can create novel electronic device applications with advanced functions using DNA as an electrically active material.In this study, we evaluated fundamental conductivity of the DNA-CTMA thin film. The J-V characteristics of DNA-CTMA single and double layer devices combined with unipolar hole (TPD) and electron (POXD) transport layers clearly demonstrated electrical conductivity of DNA-CTMA. We observed that the current density of J=590mA/cm^2 with the DNA-CTMA single layer device, J=11mA/cm^2 with the DNA-CTMA double layer device combined with TPD and J=0.02mA/cm^2 with the DNA-CTMA double layer device combined with POXD at an applied voltage of 10V. These results clearly suggest that the DNA-CTMA layer basically has bipolar carrier transport characteristics.We further evaluated fundamental conductivity of the vacuum deposited thin films of the four bases. We observed that the current density of J=180mA/cm^2 with Adenine, J=0.35mA/cm^2 with Cytosine, J=10mA/cm^2 with Guanine and J=2.3mA/cm^2 with Thymine at an applied voltage of 10V. Further, we confirmed charge carrier transport characteristics of the four bases by using them in electrophosphorescence OLEDs. Theη_<ext>-J characteristics of OLEDs with four bases as HTL were investigated. Adenine, Cytosine and Guanine as HTL demonstrated maximumη_<ext>〜8.0±0.2% demonstrating that the vacuum deposited films of the four bases are useful as a HTL in OLED.Our results dearly demonstrated that DNA double helix intrinsically have semiconducting characteristics and the DNA-CTMA and the vacuum deposited base films have potential for semiconductor applications.