Kranthiraja, Kakaraparthi Gunasekar, Kumarasamy Cho, Woosum Song, Myungkwan Park, Young Geun Lee, Jin Yong Shin, Yurim Kang, In-Nam Kim, Ajeong Kim, Hyunjung Kim, BongSoo Jin, Sung-Ho 2024-01-20T08:33:30Z 2024-01-20T08:33:30Z 2021-09-02 2014-10-28 0024-9297 https://pubs.kist.re.kr/handle/201004/126219 Two donoracceptor (DA) medium band gap polymers, P1 and P2, alkoxyphenylthiophene (APTh) linked benzodithiophene (BDT) as an electron-rich unit and 1,3-di(2'-bromothien-5'-yl)-5-(2-ethylhexyl)thieno[3,4-c]pyrrole-4,6-dione (TPD) (A1) or [5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole] (BT) (A2) as an electron-deficient unit, have successfully been synthesized via microwave-assisted Stille polymerization and utilized for bulk heterojunction (BHJ) polymer solar cells (PSCs). P1 shows a well-distinguished absorption shoulder between 590 and 620 nm attributed to the pi-pi stacking of a polymer backbone; such kind of absorption shoulder is not observed in P2, indicating that the P1 has more planar structure than that of P2. This is due to the fact that the sulfur atom of thiophene spacer and the oxygen atom of carbonyl groups in TPD have more pronounced intramolecular noncovalent interactions (INCI) in P1 than that of the sulfur atom of thiophene spacer and the oxygen atom of alkoxy groups of BT in P2. The bulk heterojunction polymer solar cells (BHJ PSCs) were fabricated with the configuration of ITO/PEDOT:PSS/polymer (P1 or P2):PC71BM/LiF/Al. The P1 device shows better photovoltaic performance with open-circuit voltage (V-oc) of 0.91 V and the power conversion efficiency (PCE) of 4.19% than the P2 device (V-oc: 0.71 V; PCE: 1.88%) in neat blend films under the illumination of AM 1.5G (100 mW/cm(2)). Upon treating the active layers containing P1 and P2 with methanol, the PCE of the P1 device is increased from 4.19 to 7.14%. In contrast, the PCE of the P2 device is decreased from 1.88 to 1.82%. Space charge limited current mobility, atomic force microscopy, transmission electron microscopy, time-of-flight secondary ion mass spectrometry, and impedance spectroscopy studies strongly support the enhanced PCE for the P1 device is attributed to the increased mobility, nanoscale morphology, and reduced resistance upon methanol treatment; these favorable properties for the P1 polymer are highly correlated with the planarity of the backbone. English AMER CHEMICAL SOC POWER CONVERSION EFFICIENCY HETEROJUNCTION SOLAR-CELLS OPEN-CIRCUIT VOLTAGE BULK-HETEROJUNCTION CONJUGATED POLYMERS MOLECULAR DESIGN BUILDING-BLOCK PERFORMANCE COPOLYMERS ENHANCEMENT Alkoxyphenylthiophene Linked Benzodithiophene Based Medium Band Gap Polymers for Organic Photovoltaics: Efficiency Improvement upon Methanol Treatment Depends on the Planarity of Backbone Article 10.1021/ma5010875 1 MACROMOLECULES, v.47, no.20, pp.7060 - 7069 MACROMOLECULES 47 20 7060 7069 scie scopus 000343949500008 2-s2.0-84908263363 Polymer Science Polymer Science Article POWER CONVERSION EFFICIENCY HETEROJUNCTION SOLAR-CELLS OPEN-CIRCUIT VOLTAGE BULK-HETEROJUNCTION CONJUGATED POLYMERS MOLECULAR DESIGN BUILDING-BLOCK PERFORMANCE COPOLYMERS ENHANCEMENT organic photovoltaic cells medium band gap polymer power conversion efficiency methanol treatment photoactive layer blend morphology