Two Linear Small Molecules Based On Oligothiophenes For Solution-Processed Organic Solar Cells

Small molecule organic solar cells?SMOSCs?have aroused considerable interest in the last decade due to their many attractive features,such as portable,flexible,easy-fabrication and large-scale manufacture potential.However,the technology of organic photovoltaic materials is not yet mature,and its power conversion efficiency need to be improved compared with inorganic solar cells.In this paper,two pairs of donor materials D9 TD and D8 TTD with were designed and synthesized based on the route of donor/acceptor energy level matching and the adjustment of donor material structure.In order to investigate their photophysical and electrochemical properties,the Density functional Theory?DFT?calculations,thermal analysis UV-Vis absorbance and cyclic voltammetry were carried out.At the same time,we fabricate the photovoltaic devices based on these new materials as donor and IC₇₀BA as acceptor,and the devices were characterized and analyzed.With the performance of the synthesized materials,we research that:The changes in the number and position of alkyl chains of oligothiophene small molecule donor materials have little effect on the thermal stability,electrochemical and optical properties of the material,and this change mainly affects the solubility of the material.Among them,D8TTD's solubility is poor because it has few alkyl chains.As a result,the contact area between the donor and acceptor is too small to form an effective photocurrent,and the power conversion efficiency of the device based D8 TTD is blow0.5%.D9TD's solubility is good because it has enough alkyl chains,so we blend it with IC₇₀BA,a high-level LUMO acceptor material,to fabricate a photovoltaic device.After annealing,device's open-circuit voltage reaches 0.97 V,and the optimized power conversion efficiency?PCE?of 9.25%for D9TD:IC₇₀BA system was achieved.