Study On The Preparation Of Large-area Organic Solar Cells By Green Printing And Its Accurate Lifetime Measurement

Organic solar cells(OSCs)have drawn widespread attention from researchers owing to their unique advantages,such as light weight,low cost,flexibility and printability.The commercialization of OSCs can be divided into two parallel processes:one is the transition from small-area devices to large-area module production(the improvement of module efficiency);the other is the transition from large-area production to commercial application(the improvement of module stability).Compared with the strongly toxic halogenated solvents,the OSCs prepared with green solvents(non-halogenated solvents)are relatively friendly to human body and the environment,and appropriate for large-area industrial fabrication.However,the high boiling point and poor solubility of green solvents make it difficult to explore and tune the morphology of large-area active layer films.In this thesis,based on the commercial application of OSCs,we investigate the relationship between shear impulse,active layer morphology and device performance by shear impulse strategy and fabricate the large-area homogenized active layer films.At the same time,we modify the thermodynamic parameters by the light intensity superposition method to predict the OSCs lifetime more accurately.First,the shear impulse strategy is applied to the preparation of large-area photovoltaic modules to realize the transformation from small-area devices to eco-friendly large-area organic photovoltaic modules.By controlling the spin-coating time and blade-coating speed to improve the shear impulse of the solution during the printing process,we systematically study the effects of the shear impulse of the solution on the film morphology and devices performance under the spin coating process and squeegee coating process,and establish the relationship between the shear impulse,active layer morphology and devices performance.For the OSCs based on the PM6(Poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))]):Y6(2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2,″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile)system,the power conversion efficiency(PCE)reached 15.1%at the blade-coating speed of 55mm/s due to the fine-tuning of the active layer films morphology.The enhancement of the shear impulse effectively inhibits the aggregation of donors and acceptors in green solvents,which facilitates exciton separation and charge translocation of devices.Meanwhile,by calculating the shear impulse under different preparation processes and investigating the corresponding active layer films morphology,we summarized the critical conditions for the formation of homogenized films.Furthermore,in order to verify the universality of the shear impulse strategy,we prepared PM6:BTP-e C9-based organic photovoltaic devices.The PCE reached 15.50%and 13.26%for the large-area(1 cm~2)rigid and flexible devices,respectively,and 11.29%for the large-area module(25 cm~2).Secondly,by using the method of luminous flux superposition and borrowing the external conditions specified by ISOS(International Conference on the Stability of Organic as well as Calcium Titanite Solar Cells).On the consideration of the motion and relaxation processes of molecular chains,we investigated the aging process of the different active layer system films under different light intensities and temperatures,and established the relationship between the amount of light radiation,films properties and devices performance.In the active layer films of the BTR-Cl:Y6(all small molecules)system,the lack of polymer molecular chain entanglement makes the small molecules more prone to movement at high light intensities,leading to their poor stability at high light intensities.Moreover,in the active layer of the OSCs based on PM6:Y6 system and PM6:PY-IT system,the movement and relaxation of polymer molecular chains is longer,resulting in faster degradation of films under the same luminous flux condition with low light intensity irradiation.In addition,we fit the PCE of the devices and propose thermodynamic correction factors for different systems(all-polymer system,polymer-small-molecule system and all-small-molecule system)with different light intensities to predict the lifetime of OSCs more accurately and concisely.