A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells

Abstract

To simultaneously achieve low photon energy loss ( E) and broad spectral response, the molecular design of the wide band gap (WBG) donor polymer with a deep HOMO level is of critical importance in fullerene-free polymer solar cells (PSCs). Herein, we developed a new benzodithiophene unit, i.e., DTBDT-EF, and conducted systematic investigations on a WBG DTBDT-EF-based donor polymer, namely, PDTB-EF-T. Due to the synergistic electron-withdrawing effect of the fluorine atom and ester group, PDTB-EF-T exhibits a higher oxidation potential, i.e., a deeper HOMO level (ca. -5.5 eV) than most well-known donor polymers. Hence, a high open-circuit voltage of 0.90 V was obtained when paired with a fluorinated small molecule acceptor (IT-4F), corresponding to a low E of 0.62 eV. Furthermore, side-chain engineering demonstrated that subtle side-chain modulation of the ester greatly influences the aggregation effects and molecular packing of polymer PDTB-EF-T. With the benefits of the stronger interchain π-π interaction, the improved ordering structure, and thus the highest hole mobility, the most symmetric charge transport and reduced recombination are achieved for the linear decyl-substituted PDTB-EF-T (P2)-based PSCs, leading to the highest short-circuit current density and fill factor (FF). Due to the high Flory-Huggins interaction parameter (χ), surface-directed phase separation occurs in the P2:IT-4F blend, which is supported by X-ray photoemission spectroscopy results and cross-sectional transmission electron microscope images. By taking advantage of the vertical phase distribution of the P2:IT-4F blend, a high power conversion efficiency (PCE) of 14.2% with an outstanding FF of 0.76 was recorded for inverted devices. These results demonstrate the great potential of the DTBDT-EF unit for future organic photovoltaic applications.

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

“…[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.…”

The Critical Impact of Material and Process Compatibility on the Active Layer Morphology and Performance of Organic Ternary Solar Cells

“…Inverted TSCs comprising DPP-LBGP, J40, and the fullerene molecule, [6,6]-Phenyl C 71 butyric acid methyl ester (PC 71 BM) were fabricated and characterized. We have optimized the ternary device results by applying various processing parameters such as processing temperatures, donor: acceptor ratios ( Figure S1 and Tables S2 and S3, Supporting Information), and solvent/additive combinations ( Figure S2 and Table S4, Supporting Information).…”

“…In recent years, organic solar cells (OSCs) have shown enormous progress primarily due to an emergence of new materials featuring proper optoelectronic properties, [1][2][3][4][5][6][7][8][9][10][11][12][13] and the Successful TSC designs incorporate combinations of two conjugated polymers and a fullerene electron acceptor molecule [18][19][20][21][22] or a polymer electron donor and two small molecules. [23][24][25][26][27][28][29][30][31] Those TSCs have to overcome material incompatibility and processing problems, which create a major bottleneck in obtaining the desirable ternary blend nanomorphologies.…”

Evaporation‐Free Nonfullerene Flexible Organic Solar Cell Modules Manufactured by An All‐Solution Process

“…[1][2][3][4][5][6] It is possible to design high-performance devices by designing photoactive materials that constitute a bulk heterojunction (BHJ), [7][8][9] device engineering, [10][11][12][13] and a combination of these. [1][2][3][4][5][6] It is possible to design high-performance devices by designing photoactive materials that constitute a bulk heterojunction (BHJ), [7][8][9] device engineering, [10][11][12][13] and a combination of these.…”