| Solar cell is a semiconductor optoelectronic device which is able to utilize solar energy effectively.It directly converts light energy into electrical energy through the photoelectric effect or photochemical effect.It contains the characteristics of cleanliness,low manufacturing cost and high efficiency.Rutile contains the characteristics of high refractive index,non-toxicity and high stability comparing with other structures of titanium dioxide.It is also an important part of solar cells.However,with the rising upsurge of nanotechnology research,devices are gradually developing towards directions of integration and miniaturization,while heat dissipation has also become a research hotspot for researchers.Therefore,researching the thermal conductivity of rutile titanium dioxide nanofilms and its influencing factors has been of great research significance in improving the performance of solar cells.Currently,experiments show that measuring the thermal conductivity of micro-nano thin films is difficult and inaccurate.Molecular dynamics simulation method is much simple to implement comparing with traditional experimental method,and can also effectively reduce the cost.This thesis aims to study thermal conductivity of rutile titanium dioxide nanofilms under circumstances of conventional conditions and oxygen vacancies through non-equilibrium molecular dynamics method in COMPASS force field.Simulations show following results:（1）The effects of film thickness and temperature on the thermal conductivity of titanium dioxide thin films were investigated.In the film thickness range of 4.74～9.47 nm,the thermal conductivity of titanium dioxide films at room temperature is 1.647～2.814 Wm-1K-1,and with the increase of film thickness,the thermal conductivity also increases.For the titanium dioxide film with a thickness of 7.10 nm,when the temperature increased from 300 K to 700 K,the thermal conductivity decreased from 2.222 Wm-1K-1 to 1.847 Wm-1K-1,and the decreasing trend was significant.（2）The effects of vacancy concentration and film thickness on the thermal conductivity of titanium dioxide thin films under oxygen-containing vacancies were investigated.At room temperature,when the oxygen vacancy concentration increased from0.065%to 0.152%,the thermal conductivity decreased from 2.161 Wm-1K-1 to 1.687 Wm-1K-1.When the film thickness increased from 5.82 nm to 8.29 nm,the thermal conductivity increased from 1.14 Wm-1K-1 to 2.285 Wm-1K-1.In this thesis,thermal conductivity of rutile titanium dioxide nanofilms is calculated and analyzed through computational simulation,which provides a theoretical basis in studying thermal conductivity which is difficult to measure.Practical reference value has been given in thermal design of solar cells and other devices. |
