首页|Optimizing the π-Bridge of Non-fullerene Acceptors to Suppress Dark Current in NIR Organic Photodetectors
Optimizing the π-Bridge of Non-fullerene Acceptors to Suppress Dark Current in NIR Organic Photodetectors
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Recently,the rapid development of non-fullerene acceptors(NFAs)has laid the foundation for performance improvements in near-infrared(NIR)organic photodetectors(OPDs).However,reducing the bandgap of NFAs to achieve strong absorption in the shorter-wave region usually leads to increased dark current density(Jd)and decreased responsivity(R),severely limiting the detectivity(D*)of NIR-OPDs.To date,it remains challenging to manipulate the Jd of NIR-OPDs through rational structure engineering of NFAs.Herein,three NIR-NFAs,namely bis(2-decyltetradecyl)4,4'-(2',7'-di-tert-butylspiro[cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene]-2,6-diyl)bis(6-(((Z)-1-(dicyanomethylene)-5,6-difluoro-3-oxo-1,3-dihydro-2H-inden-2-ylidene)methyl)thieno[3,4-b]thiophene-2-carboxylate)(TSIC-4F),bis(2-decyltetradecyl)6,6'-(2',7'-di-tert-butylspiro[cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene]-2,6-diyl)bis(4-(((Z)-1-(dicyanomethylene)-5,6-difluoro-3-oxo-1,3-d ihydro-2H-inden-2-ylidene)methyl)thieno[3,4-b]thiophene-2-carboxylate)(STIC-4F),and 2,2'-((2Z,2'Z)-(((2',7'-di-tert-butylspiro[cyclopenta[2,1-b:3,4-b']dithiophene-4,9'-fluorene]-2,6-diyl)bis(2,3-bis(5-(2-butyloctyl)thiophen-2-yl)thieno[3,4-b]pyrazine-7,5-diyl))bis(metha-neylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-lH-indene-2,1-diylidene))dimalononitrile(TPIC-4F),were designed using the thieno[3,4-b]thiophene(TT)and thieno[3,4-b]pyrazine(TPy)derivatives as the it-bridge.Owing to the intramolecular S-S and S-N interactions,STIC-4F and TPIC-4F exhibited smaller backbone distortions than下SIC-4F.A significantly red-shifted absorption with a peak at 1015 nm was observed in TPIC-4F film,larger than that(ca.960 nm)for TSIC-4F and STIC-4F films.Moreover,OPDs operating in a photovoltaic mode were successfully fabricated,and TPIC-4F-based OPDs achieved the lowest Jd of 3.18×10-8 A/cm2 at-0.1 V.Impressively,although TPIC-4F-based OPDs exhibited the lowest R,higher shot-noise-limited specific detectivity(Dsh*)in 1000-1200 nm could be achieved due to its lowest Jd.This study underscored the effectiveness of optimizing the 7T-bridge structure of NFAs to suppress Jd,ultimately attaining higher Dsh* in the NIR region.
State Key Laboratory of Luminescent Materials and Devices,Institute of Polymer Optoelectronic Materials and Devices,School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,P.R.China
National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaBasic and Applied Basic Research Foundation of Guangdong Province,ChinaBasic and Applied Basic Research Foundation of Guangdong Province,ChinaGuangzhou Science and Technology Plan Project,China
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