Construction And Properties Of Ternary Organic Solar Cells Based On Small Molecule Acceptors

Organic solar cells?OSCs?have attracted broad attention to researchers around the world for their unique advantages such as low cost,light weight,and the ability to prepare semitransparent flexible devices.However,there are still low energy conversion efficiencies?PCE?,which is difficult to prepare the thick-film and large-area devices,meanwhile,the thermal stability are very poor,which has become an important factor restricting the industrialization process of OSCs.In order to improve the PCE of OSCs and obtain organic photovoltaic materials and devices for commercial applications,in this dissertation,the small molecular non-fullerene acceptor?NFA?material as the third component was introduced into the binary system of polymer donor:fullerene acceptor?PBDB-T:PC71BM,D:FA?to prepared a ternary OSC and optimize the active layer morphology.The photovoltaic properties,thick film and large area devices,and thermal stability of the ternary OSCs were studied systematically.The main contents are as follows:1.A small molecule DTCFOIC based on seven-ring aromatic arene was designed,synthesized and used as an acceptor material blended with middle bandgap polymer donor PBDB-T to construct a binary OSC,resulting in 6.92%of PCE.On this basis,DTCFOIC was introduced as the third component into the binary system of PBDB-T:PC71BM?D:FA?to form the corresponding D:FA:NFA type ternary OSC?PBDB-T:PC71BM:DTCFOIC?.Through the systematic regulation of the material composition and additive?DIO?content in the ternary system,a higher PCE of 9.4%compared with the binary OSCs was acheived.The reason is that the addition of DTCFOIC and DIO broadens the absorption range,improves charge transfers,dissociation and collection,inhibits charge recombination,and optimizes the film morphology of the active layer.By further optimizing the active layer thickness?190 nm?and area?0.1 cm²?of the active layer,the PCE of the device is further improved up to 10.41%.Furthermore,when the area of device is further increased to 1 cm²,the PCE can still maintain over 9%.At the same time,we also studied the light and thermal stability of the ternary OSCs and found that the ternary OSCs has good photo-thermal stability and storage stability.2.A novel narrow bandgap small molecular NFA material IDT-OT based on pentacyclic aromatic arene was designed,synthesized and introduced as the third component into the binary system of PBDB-T:PC₇₁BM?D:FA?to construct the corresponding D:FA:NFA type ternary OSC(PBDB-T:PC₇₁BM:IDT-OT).Through optimization of the blend ratios of the three components and additive?DIO?content in the ternary system,the highest PCE of9.09%was obtained.In addition,the thermal stability of the ternary system was studied in detail.At 100 ^oC,after 10 min of thermal annealing,device performance of the ternary OSC can remain at 90%of the highest efficiency.Moreover,when the annealing temperature is raised to 160°C,the efficiency of the ternary system?PCE=7.69%?still remains above 80%of the highest efficiency,which indicates that the ternary system has good thermal stability.This finding implies that the introduction of small molecular NFA materials to construct a ternary OSCs is a very effective strategy for obtaining efficient and stable OSCs.