Nonfullerene Polymer Solar Cells Based on a Main-Chain Twisted Low-Bandgap Acceptor with Power Conversion Efficiency of 13.2%

Abstract

A new acceptor–donor–acceptor-structured nonfullerene acceptor, 2,2′-((2Z,2′Z)-(((4,4,9,9-tetrakis­(4-hexylphenyl)-4,9-dihydro-s-indaceno­[1,2-b:5,6-b′]­dithiophene-2,7-diyl)­bis­(4-((2-ethylhexyl)­oxy)­thiophene-4,3-diyl))­bis­(methanylylidene))­bis­(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))­dimalononitrile (i-IEICO-4F), is designed and synthesized via main-chain substituting position modification of 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)­dimalononitrile. Unlike its planar analogue IEICO-4F with strong absorption in the near-infrared region, i-IEICO-4F exhibits a twisted main-chain configuration, resulting in 164 nm blue shifts and leading to complementary absorption with the wide-bandgap polymer (J52). A high solution molar extinction coefficient of 2.41 × 105 M–1 cm–1, and sufficiently high energy of charge-transfer excitons of 1.15 eV in a J52:i-IEICO-4F blend were observed, in comparison with those of 2.26 × 105 M–1 cm–1 and 1.08 eV for IEICO-4F. A power conversion efficiency of 13.18% with an open-circuit voltage (0.849 V), a short-circuit current density of 22.86 mA cm–2, and a fill factor of 67.9% were recorded in J52:i-IEICO-4F-based polymer solar cells (PSCs), demonstrating that this main-chain twisted strategy can be a guideline that facilitates the development of new acceptors to maximize the efficiency in PSCs.

High‐Efficiency As‐Cast Organic Solar Cells Based on Acceptors with Steric Hindrance Induced Planar Terminal Group

“…The introduction of a lateral side chain at the outer position of the π bridge unit can endow the terminal moiety with a confined planar conformation due to the steric hindrance. Acceptor i-IEICO-4F [22] with the terminal group connected to the β-position of thiophene bridge unit showed a PCE of 13.18%. Moreover, the variation of side chain can significantly change the lowest unoccupied molecular orbital (LUMO) energy level of acceptors.…”

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.…”

Thermally Durable Nonfullerene Acceptor with Nonplanar Conjugated Backbone for High‐Performance Organic Solar Cells

“…The syntheses of 5,5′‐(4,4,9,9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐ s ‐indaceno[1,2‐ b :5,6‐ b ′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐3‐carbaldehyde) (1, core) and the mixture of 2‐(5‐fluoro‐2,3‐dihydro‐3‐oxo‐1 H ‐inden‐1‐ylidene)‐propanedinitrile and 2‐(6‐fluoro‐2,3‐dihydro‐3‐oxo‐1 H ‐inden‐1‐ylidene)‐propanedinitrile (7:3) (2, F‐INCN) have been previously reported. [ 23,25 ] i‐IEICO‐2F was synthesized via Knoevenagel condensation between compound 1 and F‐INCN. The final compound was characterized by 1 H‐NMR, 13 C‐NMR, and matrix‐assisted laser desorption ionization (MALDI)‐time of flight (TOF) mass spectrometer (MS).…”

“…[ 14,22 ] To improve the efficiency of NFA OSCs, the introduction of out‐of‐plane (OOP) side chains, π‐bridged segments, [ 23 ] and end groups [ 24 ] at various positions has been demonstrated to provide suitable planarity and flexibility of the main conjugated chain. [ 25 ]…”