Regulation blend film morphology molecular structural level, to enhance the performance of the photovoltaic device

Complementarity between the acceptor material to the absorption spectrum of molecular level matching, as well as good separation of nano-sized polymer morphology is the key to high efficiency solar cells. Regulation of the absorption spectrum of the photovoltaic material and molecular level can be achieved by molecular design intuitively simple strategy of many; but the morphology of the active layer is affected by many factors, the blend film morphology effective for molecular structural level achieved from regulation with a great challenge. Recently, Suzhou University Li Yongfang Academy teams Cuichao Hua Associate Professor , etc. through the polymer to the material conjugated side chain engineering, simply and effectively to achieve the optimal morphology of the blend films. They alkylthio BDT substituted thiophene units and phenyl-substituted alkylthio BDT unit NTDO copolymerized units respectively, were designed and synthesized to two polymer materials PBNT-S and PBNP-S (FIG. 1 ). PBNT-S and PBNP-S have very similar absorption spectra and molecular level, the BDT unit described two different conjugated side groups hardly influence the absorption spectrum and the energy level of the polymer. Since the BDT thienyl unit tend to distort and have a variety of conformations, and therefore a better symmetry based polymer substituted phenyl group having more than PBNP-S PBNT-S crystallinity. These two polymers are blended with the material to Y6 strong non-crystalline photovoltaic device prepared fullerene receptors, PBNT-S: significant over-crystalline Y6 blend films exhibit a phase separation structure of a large size, and PBNP- S: Y6 blend films is achieved in favor of the nano transfer excitons separated morphology. Thus, based on PBNT-S: energy conversion efficiency of only 11.10% Y6 device (fill factor of only 0.605), but based on PBNP-S: Y6 efficiency of the device is as high as 14.31% (fill factor of 0.694, as shown in Table 1). 从分子结构层面调控共混膜形貌,提升光伏器件性能

FIG. 1 (a) Chemicalstructure of PBNT-S, PBNP-S, and Y6. (B) Normalized UV-vis absorption spectraof PBNT-S and PBNP-S thin films (c) Energy level diagrams of PBNT-S andPBNP-S (d) TEM images of PBNT-S:.. Y6 and PBNP-S: Y6 blends
. table 1 Photovoltaic performance of the optimal PSCs based onPBNT-S: Y6 (1: 1.5, w / w) and pBNP-S: Y6 (1: 1.5, w / w) under the illumination of AM1.5 G at 100 mW cm -2.

the results show that, by proper engineering conjugated side chains enables precise regulation of the morphology of the blend films from the molecular structure level, to enhance photovoltaic device performance. Related research has to \”Conjugatedside-chains engineering of polymer donor enabling improved efficiency forpolymer solar cells\” was published in the \”Journal of Materials Chemistry A\” (2020, DOI: 10.1039 / D0TA01425G). The paper is included in the 2020 Journal of Materials Chemistry A Emerging Investigators Themed Issue. The first author of the paper for the Master Fan Hongyu , corresponding author for the Cuichao Hua associate professor . Papers link: https: //