Optimization Of The Zinc Oxide Electron Transport Layer In Polymer Solar Cells Based On PTB7:PC₇₁BM

Polymer solar cells based on conjugated polymer donors and fullerene acceptors are one of the reliable solutions to energy shortages because of their low cost,simple preparation method,and compatible flexible substrates.For inverted polymer solar cells（i-PSCs）,the third generation of semiconductor material zinc oxide is the most commonly used electron transport layer（ETL）material,ZnO has the advantages of high electron mobility,good optical transparency,and solution preparation.Further more,ZnO and fullerene receptors show good energy level matching.So it is meaningful to research the controllable preparation of zinc oxide.In addition,ZnO thin films prepared by solution method contains large surface defects,which will become electron traps,resulting in the decrease of interface electron collection efficiency and affecting the photovoltaic performance of the device.Based on this research background,this paper decribes a regulatory way to fabricate ZnO ETL in PTB7:PC₇₁BM based i-PSCs in an air environment,which is as follows:（1）In the sol gel system,by regulating the type of ligand,it was found that compared with ethanolamine,ZnO sol with n-propylamine and triethylamine as ligands has better performance under low temperature annealing.Annealed at 130℃and 150℃,power conversion efficiency（PCE）of the devices reach 6.98%and 6.87%.In the colloid ZnO nanoparticle system,when ZnO nanoparticles dispersed in n-butanol:methanol:chloroform=31:2.2:2.2（V/V）mixed solvent are used to fabricate electron transport layer（ETL）,the maximum PCE of the device can reach 7.91%,and the PCE can also reach 7.11%without annealing treatment of ZnO ETL.（2）Two polymetallic oxylates,1:9 and 1:12 keggin absent phosphotungstic acid（PW9 and PW11）,were synthesized and mixed with zinc oxide nanoparticle solution.When the doping concentration was 0.1 mg/m L,the PCE of the device based on ITO/ZnO-PW11-0.1/PTB7:PC₇₁BM/Mo O₃/Al could reach 8.66%,which was 18%higher than that of the control device.（3）The metal chelates of In（acac）₃ and Ga（acac）₃ were introduced into ZnO sol to prepare In-ZnO and Ga-ZnO ETL.It was found that the performance of the device based on these ETL was lower than that of the control device.Metal chelates were dissolved in isopropanol and directly spin-coated to form into In₂O₃ and Ga₂O₃ films and compounded with ZnO.The PCE of the device based on In₂O₃-ZnO composite ETL can reach 7.07%.This article has a total of 43 figures,25 tables,and 95 references.