Rational molecular design enables efficient organic solar cells and organic light emitting devices

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2022-12-26

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Alemdar Yılmaz, Eda

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Organic conjugated polymers and organic small molecules have great potential to meet one of the world's most critical challenges, clean energy production, in the following decades. Owing to their semiconducting properties, organic conjugated molecules are promising candidates for clean energy applications such as organic solar cells (OSCs) and organic light-emitting diodes (OLEDs) due to their low cost, lightweight, and flexibility. This study covers the rational molecular design for efficient OLEDs and OSCs. The first chapter covers the effect of mono-fluorine substitution of benzothiadiazole and replacing the alkoxy group with alkylthienyl on the performance of bulk-heterojunction (BHJ) OSCs. Among three benzodithiophene (BDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) bearing random polymers, the best-performing device (P-FBDT) exhibits a power conversion efficiency (PCE) of 9.21% with a fill factor (FF) of 60%, and 15.4 mA/cm2 short circuit current density (Jsc). The second chapter includes the observation of thermally activated delayed fluorescence (TADF) in conjugated systems. The effect of spin orbit coupling was demonstrated with the incorporation of a Selenium atom into the donor unit. In this study, three different OLEDs were produced using three different emitters (SeDF-G, SeDF-B, and SeDF-YG) with green, blue, and yellowish-green colors, respectively. The maximum external quantum efficiency (EQE) is 30.8%, and the maximum lumen is 17000 cd/m2 with SeDF-G based TADF OLEDs. In the third part, ternary OSCs were produced by using two polymer donors (P1 and PTB7-Th) whose absorption spectra were complementary in UV-VIS in the photoactive layer. Increasing JSC with increased absorption caused an increase in device efficiency.

Subject Keywords

Organic light emitting diodes, Solar cells, Ternary solar cells, Thermally activated delayed fluorescence

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https://hdl.handle.net/11511/101962

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

E. Alemdar Yılmaz, “Rational molecular design enables efficient organic solar cells and organic light emitting devices,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.