Preparation And Properties Of Organic Photovoltaic Materials Containing Benzobis(Thienopyran) Or Triphenylamine Derivatives

Nowadays,organic solar cells are one of the hot spots in the energy field.In this paper,a photovoltaic material containing benzobis?thienopyran?[PDT]or triphenylamine derivatives was designed and synthesized.The structural characterization of the intermediates and target products was carried out by NMR or time-of-flight mass spectrometry.The photophysical,electrochemical and photovoltaic properties of these materials were analyzed.The specific research content is as follows.?1?In order to find the acceptor unit that matches the donor unit PDT,we copolymerized PDT with three different receptor units to obtain the polymers PPDT-DFTAZ,PPDT-DSDTDFBT,and PPDT-EHDPP,respectively.Polymer solar cells were prepared by combining the polymers and fullerene acceptor material PC₇₁BM,and their photophysical properties,electrochemical properties and photovoltaic properties were explored and compared.PPDT-DFTAZ had a relatively narrow UV-vis absorption at 450⁶50 nm,but it had a higher molar absorption coefficient,leading to a higher J_sc(5.34 mA cm^-2);PPDT-DSDTDFBT and PPDT-EHDPP had a broad absorption spectrum,but their molar absorption coefficient was relatively low.In addition,PPDT-DSDTDFBT as a donor material had a obvious phase separation from PC₇₁BM.And the?_h/?_e of PPDT-EHDPP with PC₇₁BM blends was 0.030 leading to an imbalance in charge transport.All the factors limited the PCE of PPDT-DSDTDFBT and PPDT-EHDPP.Finally,PPDT-DFTAZ achieved the best PCE?2.06%?.The results indicated that we must consider factors such as energy level,carrier mobility,and film morphology in addition to spectral absorption when designing polymer donor materials.?2?Triphenylamine and its derivatives have a large steric hindrance and prevent the dye molecules from being excessively aggregated.At the same time,triphenylamine derivatives also have good hole mobility and are commonly used in the field of DSSCs.The benzothiadiazole?BT?acceptor unit is a stronger electron-withdrawing element,which can effectively adjust the LUMO level and the energy band gap and broaden its absorption spectrum.In addition,the introduction of an alkynyl group in the acceptor portion can increase the planarity of the molecule and adjust the aggregation state of the molecule.In this paper,the effects of fluorine-containing and fluorine-free BT on the photovoltaic properties of dyes were investigated when dendritic triphenylamine was used as the donor unit.At the same time,the influences of 3D triphenylamine and dendritic triphenylamine on the photovoltaic properties of dyes were further explored with fluorine-containing BT as the acceptor unit.The results showed that when the dendritic triphenylamine was used as the donor unit,the fluorine-free BT dye ZD1obtained a good PCE value(J_sc=10.58 mA cm^-2,V_oc=0.69 V,FF=73%,PCE=5.27%).And ZD1 obtained a better short-circuit current than ZD2(J_sc=8.24 mA cm^-2),which resulted from the slightly red-shifted UV-vis absorption spectrum of ZD1.In addition,when the fluorine-containing BT was used as the acceptor unit,the 3D triphenylamine dye ZD3 obtained a good PCE value(J_sc=11.18 mA cm^-2,V_oc=0.70 V,FF=70%,PCE=5.50%).And ZD3 obtained a better short-circuit current than ZD1 or ZD2,which resulted from the red-shifted UV-vis absorption spectrum of ZD3.We also added CDCA to optimize photovoltaic performance.After adding 1 mM CDCA,the PCE of the dyes ZD1,ZD2 and ZD3 increased to 5.46%,4.98%and 6.26%,respectively,which corresponded to the J_scc and IPCE values of the three dyes.