Over 14% Efficiency in Organic Solar Cells Enabled by Chlorinated Nonfullerene Small‐Molecule Acceptors

Abstract

To make organic solar cells (OSCs) more competitive in the diverse photovoltaic cell technologies, it is very important to demonstrate that OSCs can achieve very good efficiencies and that their cost can be reduced. Here, a pair of nonfullerene small-molecule acceptors, IT-2Cl and IT-4Cl, is designed and synthesized by introducing easy-synthesis chlorine substituents onto the indacenodithieno[3,2-b]thiophene units. The unique feature of the large dipole moment of the CCl bond enhances the intermolecular charge-transfer effect between the donor-acceptor structures, and thus expands the absorption and down shifts the molecular energy levels. Meanwhile, the introduction of CCl also causes more pronounced molecular stacking, which also helps to expand the absorption spectrum. Both of the designed OSCs devices based on two acceptors can deliver a power conversion efficiency (PCE) greater than 13% when blended with a polymer donor with a low-lying highest occupied molecular orbital level. In addition, since IT-2Cl and IT-4Cl have very good compatibility, a ternary OSC device integrating these two acceptors is also fabricated and obtains a PCE greater than 14%. Chlorination demonstrates effective ability in enhancing the device performance and facile synthesis route, which both deserve further exploitation in the modification of photovoltaic materials.

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

“…in single-layer solar cells, [19][20][21] demonstrating unprecedented potentials of nonfullerene acceptors for enabling high-performance photovoltaic devices for practical applications. [22,23] Along with the advancement of novel FREAs, developing appropriate donor polymers having good compatibility with acceptor materials is equally critical for attaining highperformance nonfullerene PSCs.…”

“…[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.…”

New Anthracene‐Fused Nonfullerene Acceptors for High‐Efficiency Organic Solar Cells: Energy Level Modulations Enabling Match of Donor and Acceptor

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Organic photovoltaics (OPVs) have emerged as one of the most promising renewable energy applications for their potential advantages of light weight, low cost, mechanical flexibility, and large area fabrication. [3][4][5][6][7] Although the Two new nonfullerene small molecule acceptors (NF-SMAs) AT-NC and AT-4Cl based on heptacyclic anthracene(cyclopentadithiophene) (AT) core and different electron-withdrawing end groups are designed and synthesized. [3][4][5][6][7] Although the Two new nonfullerene small molecule acceptors (NF-SMAs) AT-NC and AT-4Cl based on heptacyclic anthracene(cyclopentadithiophene) (AT) core and different electron-withdrawing end groups are designed and synthesized.

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“…[9,10] The highly tunable opto electronic properties of ADA structured materials have facilitated the optimizations of their absorption, molecular energy levels, and charge mobilities, and thus improved PCEs can be achieved in the corresponding OPVs. [5,8] As such, the simultaneous tuning of D and A units, is still on the cutting edge to further elevate photovoltaic performance. [5,8] As such, the simultaneous tuning of D and A units, is still on the cutting edge to further elevate photovoltaic performance.…”

“…[29,30] Numerous optimizations on the end groups have been conducted, such as methylation or halogenation on INCN (2(3oxo2,3dihydro1Hinden 1ylidene)malononitrile), [5,14,31] naphthylfused indanone (NINCN) (2(3oxo2,3dihydro1Hcyclopenta[b]naphthalen 1ylidene)malononitrile) with extended πconjugation area, [30,32,33] and thiophenefused unit CPTCN (2(6oxo5,6 dihydro4Hcyclopenta[c]thiophen4ylidene)malononitrile), [34] and excellent results were obtained. [29,30] Numerous optimizations on the end groups have been conducted, such as methylation or halogenation on INCN (2(3oxo2,3dihydro1Hinden 1ylidene)malononitrile), [5,14,31] naphthylfused indanone (NINCN) (2(3oxo2,3dihydro1Hcyclopenta[b]naphthalen 1ylidene)malononitrile) with extended πconjugation area, [30,32,33] and thiophenefused unit CPTCN (2(6oxo5,6 dihydro4Hcyclopenta[c]thiophen4ylidene)malononitrile), [34] and excellent results were obtained.…”