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

Alemdar Yılmaz, Eda
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.


Yaşa, Mustafa; Toppare, Levent Kamil; Arslan Udum, Yasemin; Department of Polymer Science and Technology (2022-1-27)
There are several studies on organic solar cells based on conjugated polymers in literature, and various new materials are being designed. The Donor-Acceptor approach has been the most common approach for designing and synthesizing conjugated polymers. In this study, thienopyrroledione bearing conjugated polymers were synthesized via Stille and Suzuki polycondensation reactions. In the first part of this thesis, the polymers obtained via Stille polycondensation were employed to fabricate organic solar cells...
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Toppare, Levent Kamil; Yaşa, Mustafa; Göker, Seza; Udum, Yasemin; Günbaş, Emrullah Görkem; Çırpan, Ali (null; 2018-07-06)
Inverted organic solar cells have advantages over conventional organic solar cells. Most important advantage is the improved stability of inverted solar cells. In this study, benzodithiophene, quinoxaline and selenophene bearing conjugated polymer was used as donor material in inverted solar cell applications. Device performances were investigated with the device configuration of ITO/ ZnO/ polymer:PC71BM/ MoO3/ Ag. In order to improve device performance, polymer PCBM ratio, active layer thickness, annealing...
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Cu2ZnSn(S,Se)4 (CZTSSe) compound is one of the most promising absorber materials for thin film solar cell technology due to the abundance and non-toxicity of its constituents. Besides, CZTSSe has an ideal direct band gap value in the range of 1-1.5 eV and high absorption coefficient (> 104 cm-1) in the visible region, which satisfies the conversion of the maximum amount of energy of the solar spectrum. For this, CZTSSe absorber layer with only a few microns of thickness is sufficient to absorb all the photo...
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.