Effects Of Solution Treatment On The Morphological And Interfacial Control Of Polymer Solar Cells

Improving the preparation technology are essential to industrialization of polymer solar cells. The work is focused on the morphological and interfacial control of polymer solar cells by solution treatment. The main contents of dissertation include two parts.Sodium chloride (NaCl) methanol solution process is conducted on the conventional P3HT/PC61BM polymer bulk heterojunction solar cells. The device exhibits a power conversion efficiency up to 3.36%,18% higher than that of the device without the solution process. The measurements of the active layer by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) indicate a slight phase separation in the vertical direction and a sodium chloride distributed island-like interface between the active layer and the cathode. Ultraviolet photoelectron spectroscopy (UPS) also indicate that NaCl can lower work function of the cathode. The capacitance-voltage (C-V) and impedance spectroscopy measurements prove that the NaCl methanol process can reduce the electron injection barrier and improve the interfacial contact of polymer solar cells. Therefore, this one-step solution process not only optimizes the phase separation in the active layers but also forms a cathode buffer layer, which can enhance the generation, transport, and collection of photogenerated charge carriers in the device simultaneously.Inverted and traditional structure polymer solar cells both can be processed with PEIE solution. In this research PEIE dissolved in 2-Methoxyethanol and methanol is used to optimize the devices. The experiments show that PEIE dissolved in 2-Methoxyethanol and methanol can obtain good device performance of inverted polymer solar cells. The two solvents are both good dilution. PEIE methanol solution process is conducted on the conventional PTB7/PC71BM polymer bulk heterojunction solar cells. The device exhibits a high power conversion efficiency with methanol process,35% higher than that of the device without the solution process. However, the devices with PEIE methanol process don’t obtain good performance in comparison to the methanol process, but better than without the solution process. It can be seen that PEIE did not play the role of interfacial modification. External quantum efficiency (EQE) imply high carrier collection efficiency with methanol and PEIE methanol process, and the devices with methanol process are berrer. The capacitance-voltage (C-V) indicate that the devices with methanol process obtain higher built-in voltage, then get higher open circuit voltage.This thesis mainly explored the solution process on the device performance of polymer solar cell, and analyzed the specific function and mechanism. The solution process is a great preparation technology, especially the one-step spin coating method can achieve morphological and interfacial control simultaneously, have more practical significance.