Over 14% Efficiency in Polymer Solar Cells Enabled by a Chlorinated Polymer Donor

Abstract

Fluorine-contained polymers, which have been widely used in highly efficient polymer solar cells (PSCs), are rather costly due to their complicated synthesis and low yields in the preparation of components. Here, the feasibility of replacing the critical fluorine substituents in high-performance photovoltaic polymer donors with chlorine is demonstrated, and two polymeric donors, PBDB-T-2F and PBDB-T-2Cl, are synthesized and compared in parallel. The synthesis of PBDB-T-2Cl is much simpler than that of PBDB-T-2F. The two polymers have very similar optoelectronic and morphological properties, except the chlorinated polymer possess lower molecular energy levels than the fluorinated one. As a result, the PBDB-T-2Cl-based PSCs exhibit higher open circuit voltage (V ) than the PBDB-T-2F-based devices, leading to an outstanding power conversion efficiency of over 14%. This work establishes a more economical design paradigm of replacing fluorine with chlorine for preparing highly efficient polymer donors.

Phthalimide‐Based High Mobility Polymer Semiconductors for Efficient Nonfullerene Solar Cells with Power Conversion Efficiencies over 13%

“…On the basis of the OTFT output characteristics and the threshold voltages (V T ), the difluorinated phthalimide-based polymer ffPhI-ffBT shows a larger contact resistance due to its lower-positioned HOMO energy Adv. [28,[64][65][66] Inverted PSCs with a structure of ITO/ZnO/active layer/ MoO 3 /Ag were also constructed to further evaluate the photovoltaic performance of both polymers. 2019, 6, 1801743 level, which results in a higher hole injection barrier with the Au source/drain electrodes.…”

“…[19,20,[28][29][30][31][32][33][34][35][36][37][38][39][40] To the best of our knowledge, all these high-performance donor polymers are alternating donor-acceptor (D-A) type copolymers, which are exclusively based on benzo[1,2-b:4,5-b′]dithiophene (BDT) donor unit [41] copolymerized with a few acceptor counits, such as 5,6-difluoro-2-alkyl-2H-benzo[d] [1,2,3]triazole (FTAZ), [42] benzo[1,2-c:4,5-c′]-dithiophene-4,8-dione (BDD) [43] etc. [19,20,[28][29][30][31][32][33][34][35][36][37][38][39][40] To the best of our knowledge, all these high-performance donor polymers are alternating donor-acceptor (D-A) type copolymers, which are exclusively based on benzo[1,2-b:4,5-b′]dithiophene (BDT) donor unit [41] copolymerized with a few acceptor counits, such as 5,6-difluoro-2-alkyl-2H-benzo[d] [1,2,3]triazole (FTAZ), [42] benzo[1,2-c:4,5-c′]-dithiophene-4,8-dione (BDD) [43] etc.…”

Reduced Nonradiative Energy Loss Caused by Aggregation of Nonfullerene Acceptor in Organic Solar Cells

“…[20][21][22][23][24] 3) The third loss is due to nonradiative recombination (ΔE 3 ). [29][30][31][32][33][34][35] As is known, for an OSC under open-circuit condition, an electron-hole pair at the CT state transits to the ground state by either radiative recombination or nonradiative recombination, so the electroluminescence (EL) emission can be used as a tool to monitor the nonradiative recombination. For instance, it has been demonstrated that when the ionic potential (IP) and electronic affinity (EA) of a donor are nearly aligned with those of an acceptor, the energetic offset from E g to E CT can be very small, resulting in a negligible ΔE 2 .…”

The Dawn of Single Material Organic Solar Cells

“…[67] Marcos Ramos et al synthesized a C 60 -derivatized copolymer (1) (Scheme 2), by reaction of a di-iodobenzene bearing an attached C 60 with oligo-phenylenevinylenes (nPVs) possessing a terminal alkyne. 54 P3HT and PC 61 BM showed that in spite of a higher initial PCE of 3.0%, the BHJ cell undergoes a much faster degradation under prolonged thermal treatment than the SMOSC. In 2007, Li and co-workers reported a "double-cable" polymer obtained by postpolymerization fixation of C 60 onto a polymer prepared by polymerization of a bithiophenic precursor (2).…”

“…[30,31] In the past decade, the chemistry of molecular donors has rapidly expanded and hundreds of new molecules have been synthesized and evaluated. [54][55][56] The control of the extension, structure, and properties of the D/A interfacial zone is the key to the performances of BHJ cells. [40] In recent years, several classes of donors of symmetrical structure, as exemplified in Scheme 1, have led to BHJs with PCE comparable to those of the best polymer cells.…”