Research On Organic Electronic Memory With A Bilayer Structure Of Biomolecules And Conjugated Polymers

Biomolecules have many advantages such as environmentally friendly, naturally occurring, unique electrical characteristics, which have been applied in organic electronic devices. In order to apply the biomolecules in the organic electronic memory devices, in this study, we have researched an organic electrical memory based on a bilayer of biomaterials and conjugated polymers. The used biomolecules include amino acid, peptides and proteins. Three methods of electrophoresis, spin coating and hydrothermal method have been used to prepare the biomaterials layer. Preparation, testing, characterization and the principle of the storage device were presented in this study.Biomolecules including Aspartic, Alanine and Arginine were self-assembly grown on the ITO surface by the electrophoresis method. The three types of devices structure were ITO/biomolecules/MEH-PPV/Al, which have showed hysteresis phenomenon and possessed bistable characteristics compared to the ITO/MEH-PPV/Al device. The device based on Aspartic has achieved the biggest difference of two current states for 110 n A. Besides, in order to study the performance of the device, we have changed the growth time. The results showed that the current difference of the device has increased with the increase of growth time. The ON/OFF ratio of the device can be reached to 6×102 when the growth time is 5 h.The states of biomolecules are different when using different method to grow biomolecules layer, so the storage feature will be changed. In order to improve the storage performance of devices, biomaterials include Gly-Gly, Alanine, Aspartic, and Glutamic which were self-assembly grown on the ITO surface by hydrothermal method. We have obtained three kinds of Flash-type organic nonvolatile electric memories based on Gly-Gly, Alanine and Aspartic. We have also received one WORM type organic nonvolatile electric memory based on Glutamic. The four devices based on above four biomaterials have obtained excellent storage performance. The highest ON/OFF ratio are 106, 106, 105, 105, respectively. The response time of current are not more than 20 ns and the retention time are very long. However, if it did not possess the biomaterials layer, there is no hysteresis phenomenon in the device. Therefore, the biomaterials play an important role in the memory device, which switched the device between ON and OFF states. Finally, we have investigated the effects of both different growth time of biomaterials and various thicknesses of polymer on the performance of the devices. The result showed that the former’s influence on the device is greater than the latter.Biomolecules including Gly-Gly, Proteins, Aspartic, and Glutamic were deposited on the ITO surface by spin coating. The four types of device structures are also ITO/biomolecules/MEH-PPV/Al. The device based on Gly-Gly is Flash-type organic nonvolatile electric memory, and the rest are WORM type organic nonvolatile electric memories. The response speed of the four types of those devices are less than 20 ns, showing a long retention time, and also the study found that the WORM type devices are longer than Flash-type devices. Finally, to further understand about the mechanism of the electrical conductivity transition, the I-V characteristics were analyzed by different models. We found that when the devices in the OFF state, it followed SCLC model and TE model, and it belongs to Ohmic conduction model in the ON state.