The Synthesis Of Cross-linkable Polymer Donor/Acceptor And The Stability And Photo-electrical Properties Applied For All-Polymer Solar Cell

In recent years,polymer solar cells?PSCs?have attracted wide attention,and their power conversion efficiency has exceeded 13%.However,one problem that needs to be solved is that it lacks long-term stability.Cross-linking has been proposed as an effective method to improve the stability of PSCs.All-PSCs have unique morphological stability.If cross-linking is introduced into All-PSCs,the stability will be further improved.It is expected to promote the practical application of PSCs.In this paper,we prepared two types of?D-A,?x-?D-A₂?1-x ternary random polymers consisting of one electron-donating unit?D?and two electron-deficient units?A₁,A₂?.A naphthalene diimide?NDI?unit and a thienopyrroledione?TPD?unit containing a crosslinkable group are introduced as the third component A₁ in the polymer,and the content of cross-linkable group is adjusted by the amount of A₁ For the impurities,a series of crosslinkable polymer acceptors and donor materials were synthesized.Cross-linking performance tests screen out polymers with cross-linking effect and optimal thermal annealing times.Finally,the screened donor and acceptor materials are fabricateded into all-polymer solar cellsby device optimization and device stability was test.To explore the effect on the synthesis,optoelectronic properties and stabilities of these cross-linkable?D-A₁?_x-?D-A₂?_1-x random terpolymer acceptor and donor,the following work is:1.Synthesizing NDI acceptor units containing crosslinkable groups as the third component,and obtaining a series of terpolymers X-NDI with different content of crosslinkable group by stille coupling.The acceptor materials were named 2-NDI,3-NDI,5-NDI,and Se-NDI?collectively referred to as X-NDI?,which thiophene was as D unit,NDI unit containing crosslinkable group was as A₁ unit,NDI containing crosslinkable group was as A₂ unit;secondly,crosslinkable acceptor Se-NDI was synthesized by replaceing D unit with selenylphene.The molecular weight,cross-linkable and electrochemical propertis,stability were measured.The results showed that,polymers except Se-NDI with low molecular weight had relatively high molecular weights,which was helpful for fabricating devices;when the content of cross-linkable group was ?3%,the polymers had the good cross-linkable properties,and the degree of cross-linking increased with the increasing of the content;the energy levels of all these polymers match the level of the donor material 8-TPD.2.The TPD donor unit containing the crosslinkable group as the third component was synthesized,and a series of random terpolymers with different crosslinkable groups as donor materials were obtained by the stille coupling reaction.The donor materials were named 3-TPD,5-TPD,8-TPD,and 10-TPD?collectively referred to as X-TPD?,which benzodithiophene?BDT?derivative was as D unit,TPD containing crosslinkable group was as A₁ unit,and HT-TPD-HT containing no crosslinkable group was as A₂ unit;then the donor material B-TPD was synthesized by replacing A₂ unit with TPD unit without crosslinkable group.The molecular weight,cross-linkable and electrochemical propertis,stability were measured.The results showed that the five polymers had relatively high molecular weights which was helpful for fabricating devices..When the content of cross-linkable group was ?3%,the polymers had the good cross-linkable properties,and the degree of cross-linking increased with the increasing of the content;these polymers match the energy level of the acceptor material 5-NDI.3.All-PScs were fabricated by blending acceptor material X-NDI and donor material X-TPD to screen out the best combination:5-NDI/8-TPD,and then perform the device performance on this combination.After device ptimization,such as changing thermal annealing temperature and time,solvent and additive,a energy conversion efficiency?PCE?of 3.37%was obtained.The thermal stability of the device based cross-linkable polymer 5-NDI/8-TPD was then tested compared to the devices based PTPD/TNDI without cross-linkable groups.The results showed that active layer after cross-linking has a significantly better stability than the active layer without the cross-linking.Finally,the effects of content of cross-linkble group on the device's performance and stability were investigated using external quantum efficiency?EQE?,electron/hole mobility,X-ray diffraction?XRD?,and atomic force microscopy?AFM?.