Study On Performance Improvement Of Organic Solar Cells By TiO₂ Nanoparticles

Nowadays,there is an increasing demand for energy.However,the environmental pollution(acid rain,smog,greenhouse effect,etc.)caused by the use of traditional fossil energy(natural gas,coal,and oil)has become more and more serious.Solar energy,water energy,wind energy and other new energy are gradually developed and utilized on a large scale.Based on the advantages of renewable and clean energy,the research of energy conversion devices grows vigorously.Organic solar cells(OSCs)have attracted much attention due to the low cost,good flexibility and large area of roll to roll processing.Improving exciton separation and reducing electron-hole recombination is key for OSCs to achieve high performance because of the limited exciton diffusion length in the active layers.Thus,the following research works are carried out in this paper:Inspired by light management and TiO₂ electron transport layer to improve the performance of OSCs,a simple strategy of bridging for electrons by adding TiO₂nanoparticles(NPs)into the active layer is proposed to enhance the performance of OSCs.The anatase TiO₂ NPs prepared by hydrothermal method were added to the active layer,and then the device was characterized and analyzed.It was found that?48.8%increase in power conversion efficiency(PCE),i.e.,from 2.11%to 3.14%can be achieved after adding an appropriate amount(1.0 wt%)of TiO₂ NPs.Further investigation confirms that the PCE improvement is mainly attributed to the enhanced exciton separation and reduced electron-hole recombination benefiting from the electron bridge effect played by the added TiO₂ NPs.In order to further optimize the performance of OSCs,this paper synthesized silver doped anatase TiO₂ NPs by sol-gel method and high temperature calcination.Adding silver-doped TiO₂ NPs into the active layer of OSCs further improves exciton dissociation,accelerates carriers transport and reduces electron-hole recombination.According to the current-voltage(J-V)test results of OSCs,the best performance have been achieved due to the addition of 1.0 wt%silver-doped TiO₂NPs(the molar ratio of silver to TiO₂ is 1:100)for OSCs,resulting in 61.7%improvement in PCE,from 2.01%to 3.25%for the OSCs compared with the reference device.The optimized device displays an open-circuit voltage(V_oc)of 0.54V,short-circuit current densities(J_sc)of 14.23 m A/cm²,fill factor(FF)of 42.23%,series resistance(R_s)of 14.24?·cm² and shunt resistance(R_sh)of 131.85?·cm².