Improving the all-polymer solar cell performance by adding a narrow bandgap polymer as the second donor

Fluorination effects on bithiophene unit in benzodithiophene-4,8-dione based D-A type alternating copolymers for highly efficient polymer solar cells

In this study, two D-A polymers consisting of benzodithiophene-4,8-dione and tetrathiophene with or without fluorination were synthesized to reveal the photovoltaic properties of fluorination effect on the polymer backbone. Polymer PDFTB with two fluorine atoms substituted on the backbone exhibits an enhanced π-π stacking effect, deeper HOMO energy level and better backbone planarity than PDTB without fluorine atom substitution. Devices based on PDFTB:ITIC show a power conversion efficiency of 4.39%, which is 15% higher than that of PDTB-based devices due to the higher hole mobility, optimized surface morphology and homogeneous phase separation of the active layer. These results suggest that the fluorination strategy is a facile way to design polymeric donors for solvent-processed polymer solar cells.

Linker Unit Modulation of Polymer Acceptors Enables Highly Efficient Air-Processed All-Polymer Solar Cells

A group of regioregular polymer acceptors is synthesized by polymerizing Y6 moieties with different linker units including thiophene, vinylene, 2,2'-bithiophene, and thieno[3,2-b]thiophene, and their optoelectrical properties and photovoltaic performances are studied systematically. It is found that the linker units have significant impacts on the backbone planarity, conjugation, and hence optoelectrical properties of polymer acceptors. The vinylene-based PYF-V-o polymer shows a smaller dihedral angle between the end groups and vinylene units and a more rigid polymer backbone, thus affording bathochromic absorption and better electron-transporting capacity. As a result, the PM6:PYF-V-o based all-polymer solar cells (all-PSCs) are able to achieve the highest power conversion efficiency of 16.4% with an unprecedented small voltage loss of 0.49 V. Moreover, the PM6:PYF-V-o blend exhibits good resistance to environmental stressors and the air-processed PM6:PYF-V-o cells can still maintain a high efficiency of 16.1%, which is the best air-processed all-PSC efficiency reported to date. This study provides the structural-property guidance that can be used to facilitate the development of polymer acceptors for all-PSCs.

A high-voltage non-aqueous hybrid supercapacitor based on the N2200 polymer supported over multiwalled carbon nanotubes

P(NDI2OD-T2), also known as Polyera ActivInk N2200, is a widely accepted non-fullerene acceptor polymer that is used prominently in the energy harvesting application due to its ease of synthesis, high electron mobility, and other desirable semiconducting properties. With its recent foray into energy storage applications, there is tremendous potential for developing composites of N2200 with carbon nanotubes (CNTs) to improve its electrical properties and extend its applicability. Here we report a facile synthesis of an N2200 composite with multiwalled carbon nanotubes (MWCNTs) following an in situ approach to include MWCNTs into the polymer matrix, improving its electrochemical performance in an organic electrolyte (1 M LiClO₄/propylene carbonate). The composite material with an optimum MWCNT content exhibits prominent redox behavior delivering a specific capacity of 80 mA h g^-1_(polymer) in a standard three-electrode cell. Moreover, the N2200/MWCNT composite material showing a battery-type electrochemical signature could perform as an efficient negative electrode in a high-voltage (2.4 V) hybrid supercapacitor device comprising capacitive activated carbon as the positive electrode.