Preparation And Performance Of Cathode Interfacial Layers Based On Perylene Diimide

Organic solar cells（OSCs）have attracted extensive attention from academia and business due to their superiorities of light weight,physical flexibility,solution processing,and ease of fabrication.The energy conversion efficiencies（PCEs）of OSCs have been gradually improved in recent years,which not only depends on the design and synthesis of novel donor and acceptor materials,but also is closely related to device optimization.Among them,interface engineering plays an important and irreplaceable role,especially cathode interface layers（CILs）.CILs can reduce the work function of metal cathode,improve the charge selectivity of electrode,adjust the morphology of active layer,enhance device stability,improve device performance and so on.Furthermore,in order to meet the requirements of future industrial production,cathode interface materials（CIMs）also need to have the advantages of low cost,easy synthesis,low temperature solution processing,and good thickness insensitivity.In this paper,two kinds of conjugated small molecule CIMs were synthesized through simple one-step reaction,and their influence on fullerene and non-fullerene systems was investigated in detail.The corresponding contents are as follows:Two conjugated small-molecule CIMs,PDINOH and PDINOH-4Cl,were prepared by one-step reaction of 3,4,9,10-tetracarboxylic anhydride and 1,6,7,12-tetrachloro-3,4,9,10-tetracarboxylic anhydride with N-（3-aminopropyl）ethanolamine,respectively.We applied these two kinds of CIMs to PTB7-Th:PC₇₁BM system,respectively,and prepared inverted devices.It is found that when the film thickness of PDINOH CIL was 10 nm,the device obtained the optimal efficiency of 10.60%when the film thickness of PDINOH-4Cl CIL was 12 nm,the device achieved the optimal efficiency of 7.47%.Moreover,when the thicknesses of PDINOH and PDINOH-4Cl were 34 nm and 38 nm,the device performances maintained 92.45%and 88.22%of the optimal PCEs,respectively.These results showed that PDINOH and PDINOH-4Cl CILs are conducive to improving device performances and have excellent thickness insensitive performance.However,the modification effects of PDINOH-4Cl CIL did not reach the desired effect,which might be the strong electronegativity of Cl atoms,limiting to electrons transmission and dissociation.This study provides an important reference for the subsequent design and synthesis of small molecule CIMs and the needs of future industrial production.The PDINOH conjugated small molecule CIL material was applied to PM6:Y6non-fullerene system and other systems to further explore its influences on device performances.The results indicated that the PDINOH-modified conventional device achieved 17.08%PCE in PM6:Y6 non-fullerene system.Furthermore,the device spin-coated a layer of MeOH between the active layer and PDINOH CIL showed an excellent PCE of 17.60%and high FF of 78.32%.And it also showed exceptional stability in a glove box filled with nitrogen and under the absence of encapsulation situation,the PCE still retained around 80%of its foremost value after 150 days.Even if the film thickness of PDINOH（MeOH）CIL is 34 nm,the PCE of device still reached16.60%.In addition,PDINOH is CIM owing outstanding universal properties,which is applied to the active layers of PTB7-Th:PC₇₁BM or PTB7:PC₇₁BM fullerene OSCs systems,PM6:IT-4F,PTB7-Th:ITIC or PM6:Y6 non-fullerene OSCs systems and PTB7-Th:N2200 all-polymer OSCs system were beneficial to improve their photovoltaic performances.These results indicated that PDINOH is an outstanding CIM that can effectively improve device photovoltaic performances,stability,and thickness insensitivity.And this study provides a choice for small-molecule CIMs required for industrial production in the future.