| Organic optoelectronic devices have attracted great attention from academia to industry due to their unique applications in full-color display,solid state lighting,solar cells,thin film transistors,sensors and energy storage fields.Recently,significant advances have been made in this cutting-edge field,such as active matrix organic light-emitting diodes?OLEDs?that have been commercialized for smartphones,televisions and portable devices.Simultaneously,the power conversion efficiency of solution-treated organic solar cells?OPVs?has exceeded 15%,which meet the fundamently commercial requirements.However,the reliability research on optoelectronic devices under extreme environments is highly urgent neeed to further investiage and improve.The optoelectronic measurement system for extreme condition,photoelectric properties of organic semiconductor materials and the opto-physics,electro-optical properties of electronic devices under extreme conditions are rarely reported.In this context,we develop fundamental and applicable research combining the basic theory of organic optoelectronic devices,photoelectric conversion mechanism and process.In this thesis,the literature review and theoretical analysis for the factors afflecting the reliability of optoelectronic devices are firstly demonstrated,and the improvement mechanism for the reliability of organic optoelectronic devices under oxidation,water vapor,chemical,temperature and photooxidation conditions are discussed in detail.It is found that each individual semiconducting layer inside the device tends to cause the degradation of the intrinsic semiconductor properties or decreasion of the device performance due to a variety of reasons.More importantly,the interaction of layer-layer and the environment caused their degradation lead to further degradation of the physical and chemical properties of the semiconductor film.In particular,the oxidizing environment condition results in degradation of electrical properties owing to oxidants,ozone,and condensation into water vapor;the water vapor environment lead to exciton dissociation of the active layer in the solar cell and short operation lifetime due to penetration or invasion of water molecules;the chemical substance is more permeable than the water molecule,and the robustness of the liquid phase organic solvent and the acidic/alkaline solution is more difficult to obtain than the aqueous atmosphere;For high temperature,the crystal structure of the semiconductor material is easily deformed by heat induced by high temperature,and many organic semiconductor materials encounter typical mechanical stress problems derived from thermal expansion;The photooxidation of oxygen molecules and the dimerization under illumination in photooxidation environment condition are likely to cause photoreaction of acene materials,and photooxidation can seriously decrease the electrical properties of some high crystallinity materials or the blending of certain organic materials.In addition,this thesis discusses in detail the improvement mechanism of the reliability for organic optoelectronic devices under oxidation,water vapor,chemical,high-temperature and photooxidation conditions.Then,the influence of extreme high-pressure conditions on the reliability of under different pressure intensity and time has been systematically studied for organic semiconductor functional layers and OLEDs devices.The surface morphology,photophysical and electrical characteristics of p-type,n-type and emissive semiconductors under different pressuring intensity and time are presented.By using the high-pressure of 0.75 MPa,the current density increases gradually for single hole/electronic devices with the pressure time of 5 min,10 min to 20 min.The main reason is attributed to the reduction of the intrinsic thickness for the organic film.As the pressing time increases,the electric field strength of the carrier movement is strengthened,thus the mobility is improved,and the electrical characteristics of the semiconductor layer are improved.In addition,by applying pressure on the entire organic light-emitting device and a specific functional layer inside the OLEDs device to investigate the effects of different extreme pressure and pressuring times on the optoelectronic properties of the OLEDs device.We have demonstrated that the extreme pressure enables imbalance of carrier injection,transportation and recombination in OLEDs devices,which decreases,even accelerate degradation of the devices.At the same time,the organic molecules from the emissive layer of the device under the extreme pressure condition is easily diffuse to the adjacent transport layer?particularly for the ultra-thin emissive layer structure?and causing other negative effects including molecular aggregation,inducing polarons,vacancies and defects.More improtantly,the electroluminescence properties of the OLEDs were significantly improved by employing the extreme pressure to the specific functional layer.An approximately 20.1%improvement in current efficiency,from 3.33 to 4.00cd A-1,was obtained compared to the OLEDs with non-pressure.Furthermore,this thesis investigated OLEDs reliability under the extreme low-temperature conditions.An ultra-low temperature OLEDs measurement system with low temperature range of-70?25°C was designed and developed to study the OLEDs reliability under extreme low temperature.The system functions as low temperature,vacuum and optoelectric measurement,mainly consist of the low temperature,cavity,sensing and test unit.On this basis,we investigated the optoelectric reliability of single-carrier and OLEDs devices at room temperature,freezing point 0°C and different low temperatures.The devices in the vacuum chamber at room temperature avoids the influence of water and oxygen from the ambient atmosphere,and hence improve their electrical characteristics.For the condition of 0?,the low temperature reduces the heat loss caused by the thermal movement of the internal carriers of the device,thereby further improving the electrical characteristics of the device.Interestingly,the current density of the device is gradually reduced as the temperature decreases from 0°C to-10°C,-20°C to-40°C.A detailed discussion from the thermal motion,drift motion and diffusion motion of carriers are conducted.Also,the low-temperature reliability of OLEDs with fluorescence and phosphorescence characteristics is presented,respectively.During the device operation,charge carrier trapping effect by luminescent dopant molecules is dominated mechanism.The low-temperature induced low carrier injection and transportation properties,and charge carrier imbalance accelerate the deterioration of device performance.Finally,research have focused on the reliability of organic solar cells under illumination conditions.We investigated the variation of electrical properties of electron-only devices under optical radiation conditions.On the basis of that,the typical P3HT:PCBM active layer-based solar cell devices were fabricated,and the electrical and photophysical properties of devices on the different illumination times,especially continuous illumination,were demonstrated.Moreover,the light-induced S-type J-V characteristic curves were also presented.Although the devices exhibit lower FF and Jsc under initial illumination,significantly improve over time under continuous illumination.The results indicate that the Li F modified Zn O functional layer can effectively reduce the trap state density from the electronic extraction layer/active layer interface,enhance the electron extraction efficiency,and shorten the light immersion time required for trap filling.Therefore,the Li F modified Zn O-based OPVs device quickly reach a stable state under the illumination of 30 s,and an approximately 21.19%improvement in power conversion efficiency was obtained compared to the pristine Zn O-based OPVs,indicating that the Li F modified Zn O-based OPVs device has enhanced structural stability under the action of light radiation,thus ultimately improve the device performance degradation caused by illumination changes. |
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