Son, Seon Kyoung Kim, Youn-Su Son, Hae Jung Ko, Min Jae Kim, Honggon Lee, Doh-Kwon Kim, Jin Young Choi, Dong Hoon Kim, Kyungkon Kim, BongSoo 2024-01-20T10:31:20Z 2024-01-20T10:31:20Z 2021-09-05 2014-02-06 1932-7447 https://pubs.kist.re.kr/handle/201004/127101 We synthesized four polymers (pT3DPP-HD, pT3DPP-OD, pT2TTDPP-HD, and pT2TTDPP-OD) and characterized their photovoltaic properties as a function of the backbone planarity, alkyl side chain length, and film morphology. The polymers were donor-acceptor type low-band-gap (1.2-1.3 eV) polymers employing terthiophene (T3) or thiophene-thieno[3,2-b]thiophene-thiophene (T2TT) as the donor and 2,5-bis(2-hexyldecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione (DPP-HD) or 2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4-(2H,5H)-dione (DPP-OD) as the acceptor. The T2TT moiety in the polymer backbone is more planar than the T3; the OD moiety as the alkyl side chain ensured a higher solubility than the HD moiety. Polymer solar cells (PSCs) were fabricated, and their properties were characterized. The photoactive layer consisted of one of the four polymers and one of the fullerene derivatives (PC70BM or PC60BM). For a given fullerene derivative, the PCEs prepared with each of the four polymers were ordered according to pT3DPP-OD, pT2TTDPP-HD, pT3DPP-HD, and pT2TTDPP-OD. Studies on the morphologies of the polymer:fullerene layers revealed that the pT3DPP-OD:PC70BM blend exhibited an optimal degree of phase separation between the polymer and the fullerene, while retaining a high degree of interconnectivity, thereby yielding the highest PCE measured in this series. By contrast, the pT2TTDPP-OD:fullerene yielded the lowest PCE because of too high crystalline fibrous polymer domains. In conclusion, we demonstrate that minute variations in the polymer chemical structure strongly affects both (i) the nanoscale miscibility between the polymers and fullerenes and (ii) the interconnectivity of the polymer chains, and these properties are tightly correlated with the solar cell performance. English American Chemical Society LOW-BANDGAP POLYMER ALKYL SIDE-CHAIN PHOTOVOLTAIC PROPERTIES CHARGE-TRANSPORT GAP POLYMERS DIKETOPYRROLOPYRROLE EFFICIENCY MOBILITY BENZODITHIOPHENE SEMICONDUCTORS Correlation between Polymer Structure and Polymer:Fullerene Blend Morphology and Its Implications for High Performance Polymer Solar Cells Article 10.1021/jp405744d 1 The Journal of Physical Chemistry C, v.118, no.5, pp.2237 - 2244 The Journal of Physical Chemistry C 118 5 2237 2244 scie scopus 000331153700001 2-s2.0-84893826449 Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Chemistry Science & Technology - Other Topics Materials Science Article LOW-BANDGAP POLYMER ALKYL SIDE-CHAIN PHOTOVOLTAIC PROPERTIES CHARGE-TRANSPORT GAP POLYMERS DIKETOPYRROLOPYRROLE EFFICIENCY MOBILITY BENZODITHIOPHENE SEMICONDUCTORS Polymer solar cells Low band gap polymers Power conversion efficiency Crystalline structure Film morphology