Yarı İletken Polimerlerin Bant Aralıklarının ve Osilatör Güçlerinin Kuantum Mekaniksel Yöntemlerle Araştırılması
![](/xmlui/themes/Mirage2//images/mime2.png)
Göster/ Aç
Tarih
2020-02-19Yazar
Ramazanli, Ahmad
Ambargo Süresi
Acik erisimÜst veri
Tüm öğe kaydını gösterÖzet
In recent years, polymers have started to replace metals in many applications with
the discovery of their conductivity. Easy preparation, low costs, corrosion resistance
and light weight of polymers make them advantageous over metals. It was first
discovered in the 1950s that the polymers themselves could be conductive without
being directly coupled to any metal, and since then, studies focused to improve the
conductivity of the polymers. Applications of conductive polymers include organic
solar cells, electronic circuits, organic light emitting diodes, actuators, chemical and
bio-sensors. Conductivity in polymers is explained with the help of band gap theory.
If there is an energy difference of 9 eV or more between the valence band and the
conductivity band, this polymer is insulating. If this energy difference ranges from
0.1 to 4 eV, it is a sign that the polymer is a semiconductor. In conductive polymers,
the valence band and the conductivity band are overlapped. Conductivity properties
of polymers can be studied both experimentally and theoretically. Although reliable
results are obtained in experimental techniques, the synthesis and separation
processes carried out in the laboratory take long time. However, with the help of
iv
computers and advanced softwares, a lot of information about polymers can be
easily obtained by theoretical studies. Quantum mechanical methods which are an
important branch of theoretical studies may be classified as Semi-Empirical, Ab
Initio and Density Functional Theory (DFT). In this study, band gaps and oscillator
strengths were calculated for polyacetylene (trans and cis structured),
polythiophene, poly(p-phenylene) and poly(p-phenylene vinylene) by using
configuration interaction singles (CIS) method with density fitting technique (DF).
These values of the polymers considered were obtained by TD-DFT (timedependent
density functional theory) technique and both methods were compared
with each other and with the experimental data in the literature. The results show
that while the TD-DFT technique is very close to the experimental data, the values
calculated by CIS method are slightly higher than both TD-DFT values and
experimental results.