The Development Of Diketopyrrolopyrrole Derivatives/CdS-Based Photovoltaic Materials And Devices

In this paper,we designed and synthesized several small organic molecules in which contain one-dimensional or two-dimensional structure.Diketopyrrolopyrrole?DPP?was used as the small molecule building unit,benzo[1,2-b:4,5-b'] dithiophene?BDT?with different side groups and pyrene was introduced as donor unit and terminal group respectively.The photovoltaic properties of small molecules were characterized by two kinds of device structures?ITO/PFN /Small Molecule:PC61BM/MoO3/Ag and ITO/CdS/Small Molecule:PC61BM/MoO3/Ag?.The main results are submitted as flow :Firstly,by Stille coupling,2,6-bis?trimethyltin?-4,8-bis[?2-ethylhexyl?oxy]benzo[1,2-b:4,5-b']dithiophene and 2,6-bis?trimethyltin?-4,8-bis?triisopropylsilylethynyl?benzo[1,2-b:4,5-b']dithiophene reacted with 3-?5-bromo-thiophen-2-yl?-2,5-bis-?2-hexyl-decyl?-6-?5-pyrene-2-yl-thiophen-2-yl?dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione,two kinds of organic small molecules with one-dimensional structure were synthesized,namely BDT-OEH-2DPPPY and BDT-TIPS-2DPPPY,their optical bandgap were 1.55 and 1.52 eV,EHOMO were-5.17 and-5.24 eV,and ELUMO were-3.62 and-3.72 eV,respectively.PFN was used as the battery device electronic transport layer,when the mass ratio of BDT-OEH-2DPPPY:PC61BM was 1:1,the highest power conversion efficiency?PCE?of the solar cell was 1.30%,and its open circuit voltage(V_OC)was 0.74 V,short circuit current density?JSC?was 4.21 mA/cm²,filling factor?FF?was 42%.When the mass ratio of BDT-TIPS-2DPPPY:PC61BM was 1:1,the highest PCE was 0.66%(V_OC=0.78 V,JSC=1.19 mA/cm²,FF=71.19%).Used CdS as the electron transport layer,BDT-OEH-2DPPPY:PC61BM=1:1?w/w?as the optical active layer,the PCE was 1.11%(V_OC=0.7 V,JSC=2.68 mA/cm²,FF=58%),BDT-TIPS-2DPPPY:PC61BM=1:1?w/w?optical active layer,the PCE was 0.5%(V_OC =0.78 V,JSC = 0.78 mA/cm²,FF=58%).Secondly,2,6-bis?trimethyltin?-4,8-bis?4,5-dioctyl-thiophen-2-yl?benzo[1,2-b:4,5-b']dithi-ophene and 2,6-bis?trimethyltin?-4,8-bis?5-octylthio-thiophen-2-yl?benzo[1,2-b:4,5-b']dithiophene were synthesized.By Stille coupling reaction between the above mentioned monomers and 3-?5-bromo-thiophen-2-yl?-2,5-bis-?2-hexyl-decyl?-6-?5-pyrene-2-yl-thiophen-2-yl?dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione,two organic small molecules with two-dimensio-nal structure were synthesized,namely BDT-T-2DPPPY and BDT-TS-2DPPPY,their optical bandgap were 1.54 and 1.52 eV,EHOMO were-5.23 and-5.18 eV,ELUMO were-3.69 and-3.66 eV,respectively.Used PFN as the electron transport layer,BDT-T-2DPPPY:PC61BM was1:2?w/w?as the optical active layer,the solar cell device efficiency was relatively high,which was 0.60%(the V_OC was 0.72 V,JSC was1.67 mA/cm²,FF was 50.30%).When the mass ratio of BDT-TS-2DPPPY:PC61BM was 1:2?+3% CN?,the solar cell device efficiency wasrelatively up to 0.38%(V_OC = 0.69 V,JSC = 0.82 mA/cm²,FF=67.5%).As the CdS used as the electron transport layer,the mass ratio of the optical active layer BDT-T-2DPPPY:PC61BM was 1:1,the PCE was 0.48%(V_OC = 0.68 V,JSC =1.67 mA/cm²,FF=42%),and the mass ratio of BDT-TS-2DPPPY:PC61BM was 1:1,PCE was 0.78%(V_OC =0.73 V,JSC =1.85 mA/cm²,FF=58%).Thirdly,by Stille coupling,2,7-bis?trimethyltin?5,10-bis?4,5-dinecylthiophen-2-yl?dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene reacted with 3-?5-bromo-thiophen-2-yl?-2,5-bis-?2-hexyl-decyl?-6-?5-pyrene-2-yl-thiophen-2-yl?dihydro-pyrrolo[3,4-c]pyrrole-1,4-di-one,and then got the small molecule DTBDT-T-2DPPPYwith a larger conjugate area and longer conjugate length,which optical band gap was 1.6 eV,EHOMO was-5.18 eV,ELUMO was-3.58 eV.The highest power conversion efficiency was 0.81%(V_OC =0.65 V,JSC =2.59 mA/cm²,FF= 47.43%)when PFN was used as the electron transport layer and the mass ratio of DTBDT-T-2DPPPY:PC61BM was 1:1,and used CdS as the electron transport layer,the optical active layer?DTBDT-T-2DPPPY:PC61BM=1:1,w/w?,PCE was 1.08%(V_OC=0.7 V,JSC =2.34 mA/cm²,FF =64%).