Effect Of Solvent Vapor Annealing On Polythiophene And Fullerene Solar Cell

Organic solar cell(OSC) is a promising photovoltaic technology for clean and renewable energy source due to its superior properties such as mechanic flexibility, light weight, visible transparency and large-area manufacturing compatibility, and OSC is one of the main research directions in the field of green energy. However, the power conversion efficiency(PCE) of OSC has not yet reached commercial standard. In order to improve the PCE, we investigated the influence of solvents vapor annealing(SVA) on the performance of OSC based on polythiophene and fullerene. Effect of hydrochloric acid SVA on the morphology of spray coated silver electrode has also been studied. This paper paved the way for all solution processed large scale OSC. The works can be divided into three parts:1. The operation parameters for the solar active layer were optimized. We fabricated the active layer by spin coating technology, and studied the influence of spin coating time and speed on the active layer. As the spin coating time increased, the PCE of the device was shown to be increased at first and then decreased. Effect of spin coating speed on the PCE of devies was similar to the spin coating time. The results exhibited that the optimized operation parameters for spin coating were 60 s and 1000 rpm, leading to the highest PCE of 6.55%.2. Effect of SVA treated OSC with the structure of ITO/ZnO/PTB7:PC71BM/MoO3/Ag was systematically investigated by applying different polar solvents, including methanol, ethanol, dimethylsulfoxide, acetone and isopropanol. By analyzing the variation of OSC performance and the morphology of active layer, the results showed that both the solubility parameters and viscosity of solvent played an important role in controlling the morphology of PTB7:PC71BM blend. Especially, the OSC treated by methanol with high solubility parameters and low viscosity exhibited a remarkable enhancement of PCE from 6.55% to 8.13%. The mechanism of polar solvents for SVA treatment was elucidated through characterizing both the morphology of active layers by atomic force microscope and the charge carrier mobility by theoretic simulation using space charge limited current.3. Hydrochloric acid SVA was incorporated to modify the spray coated silver electrode, and the effect of hydrochloric acid on the performance of silver electrode was studied. The results showed that hydrochloric acid SVA could improve the conductivity of spray coated silver electrode and eliminate the boundary diffraction effect during spray coating process, resulting in a significant decrease of electrode boundary width from 4.91 μm to 1.14 μm. To elucidate the mechanism of SVA, the morphology of silver electrode was characterized by means of metallographic microscope, scanning tunneling microscope and energy dispersive X-ray spectroscopy.