Study On Assembly And Performance Of Organic Solar Cell Devices Based On Small Molecule Acceptors

Organic solar cells are a new energy technology that directly converts solar energy into electrical energy.The devices have received comprehensive attention because of light weight,low cost,flexibility,and suitability for roll-to-roll printing.The active layer materials in the structure of organic solar cells play a decisive role in the photovoltaic performance of the devices.It has been a research hotspot to improve the photovoltaic efficiency of devices through the development of different active layer materials.Non-fullerene small molecule acceptor materials in active layer materials have developed rapidly in recent years due to their specific molecular weight,easy adjustment of carrier mobility and energy levels,and no batch-to-batch differences.In this dissertation,organic solar cells based on non-fullerene small molecule acceptors are chose as research objects,and the performance of devices based on three types of acceptor materials has been optimized.The specific research content and results are as follows:1.By changing the benzene ring in the IDT core of IDIC to the naphthalene ring,the fused ring small molecule acceptor material NDIC is designed.Compared with IDIC,NDIC has a wider optical band gap and a higher LUMO energy level.OSCs are fabrictated with PBDB-T as donors and IDIC/NDIC as accepters.The open-circuit voltage of PBDB-T:NDIC based devices significantly increases,in contrast to that of PBDB-T:IDIC based devices.The effects of solvent additives and thermal annealing on the active layer are further studied.Finally,PBDB-T:NDIC based devices achieve a high power conversion efficiency?PCE?of 9.43%.2.Novel perylenediimide?PDI?dimers PDI-T and FPDI-T are designed by different fused ring design strategies.The bridging compounds of PDI-T and FPDI-T are disubstituted and tetrasubstituted ethylene,respectively.Compared to PDI-T,FPDI-T has a more distorted structure and a red-shifted absorption.In addition,these two moleculars both have thiophene units.Thus,the photovoltaic performance of the two corresponding PDI dimers without thiophene units is also studied.The study finds that PDI-T and FPDI-T with thiophene units have relatively high photovoltaic performance.After adjusting donor-acceptor ratios and adding solution additives,PBDB-T:FPDI-T based devices have the most excellent photovoltaic performance with a PCE of 7.5%.3.Novel non-fused ring small molecule acceptors OC₂-IC and TP₂-IC are designed by being connected to side chains with different sizes.The side chains of the central units of OC₂-IC and TP₂-IC are methyl and tertiary butyl,respectively.Compared to OC₂-IC,TP₂-IC has wider light absorption range in the UV-vis light region.In addition,the central core of TP₂-IC has better planarity,which is benefical to molecule stacking and further improve charge transfer performance.After adjusting donor-acceptor ratios,the devices fabrictated with PBDB-T as the donor and TP₂-IC as the accepter obtain a PCE of 6.43%.