A Twisted Thieno[3,4‐b]thiophene‐Based Electron Acceptor Featuring a 14‐π‐Electron Indenoindene Core for High‐Performance Organic Photovoltaics

Abstract

With an indenoindene core, a new thieno[3,4-b]thiophene-based small-molecule electron acceptor, 2,2'-((2Z,2'Z)-((6,6'-(5,5,10,10-tetrakis(2-ethylhexyl)-5,10-dihydroindeno[2,1-a]indene-2,7-diyl)bis(2-octylthieno[3,4-b]thiophene-6,4-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (NITI), is successfully designed and synthesized. Compared with 12-π-electron fluorene, a carbon-bridged biphenylene with an axial symmetry, indenoindene, a carbon-bridged E-stilbene with a centrosymmetry, shows elongated π-conjugation with 14 π-electrons and one more sp carbon bridge, which may increase the tunability of electronic structure and film morphology. Despite its twisted molecular framework, NITI shows a low optical bandgap of 1.49 eV in thin film and a high molar extinction coefficient of 1.90 × 10 m cm in solution. By matching NITI with a large-bandgap polymer donor, an extraordinary power conversion efficiency of 12.74% is achieved, which is among the best performance so far reported for fullerene-free organic photovoltaics and is inspiring for the design of new electron acceptors.

Dithieno[3,2‐b:2′,3′‐d]pyrrol Fused Nonfullerene Acceptors Enabling Over 13% Efficiency for Organic Solar Cells

“…[29][30][31][32][33][34][35][36][37] Based on the Shockley-Queisser efficiency limit model, the ideal bandgap (≈1.34 eV) of the photoactive layer for AM 1.5G illumination could achieve the optimal photovoltaic performance. [30,[39][40][41][42] Zhan and co-workers [43] and Jen and co-workers [44] have reported a fused-ring thiophenethieno [3,2-b]thiophene-thiophene-based hexacyclic low-bandgap NFA (named IHIC or 4TIC, 1.38 eV), exhibiting a PCE of 9.77% with an relative high visible transmittance. [30,[39][40][41][42] Zhan and co-workers [43] and Jen and co-workers [44] have reported a fused-ring thiophenethieno [3,2-b]thiophene-thiophene-based hexacyclic low-bandgap NFA (named IHIC or 4TIC, 1.38 eV), exhibiting a PCE of 9.77% with an relative high visible transmittance.…”

“…[38] Guided by this predictive principle, several methods have been developed to broaden the absorption spectra of NFAs, such as extending the conjugation and enhancing the ICT effect. [30,[39][40][41][42] Zhan and co-workers [43] and Jen and co-workers [44] have reported a fused-ring thiophenethieno[3,2-b]thiophene-thiophene-based hexacyclic low-bandgap NFA (named IHIC or 4TIC, 1.38 eV), exhibiting a PCE of 9.77% with an relative high visible transmittance. Hou and coworkers [45] have demonstrated an ultranarrow-bandgap NFA (IEICO-4F, 1.24 eV) through utilizing a spacer (alkoxy thiophene) to enhance the ICT effect and electron delocalization, indicating a PCE of 10.9% within a ternary OSC.…”

Accurate Determination of the Minimum HOMO Offset for Efficient Charge Generation using Organic Semiconducting Alloys

“…[6][7][8] However, this leads to large energy losses (>0.60 eV), as defined by E loss = E g opt − qV oc , (E g opt is the optical bandgap, V oc is the open-circuit voltage, and q is elementary charge), and limits the power conversion efficiency (PCE) to less than 12% [9][10][11][12][13][14] after decades of effort. [22][23][24][25][26][27][28][29][30][31][32][33] For such a material combination, a large ΔE LUMO always exists, which reduces the highest occupied molecular orbital (HOMO) offset [ΔE HOMO = E HOMO(D) − E HOMO(A) ] to minimize energy loss [34][35][36][37] while enhancing the light collection in near-infrared (NIR) [15][16][17][18][19][20][21] To form a complementary absorption, current popular NFA OSCs are based on the combination of a widebandgap donor and a narrow-bandgap acceptor.…”

Side‐Chain Impact on Molecular Orientation of Organic Semiconductor Acceptors: High Performance Nonfullerene Polymer Solar Cells with Thick Active Layer over 400 nm

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Compared with traditional fullerene acceptors such as [6,6]-phenyl-C61/C71-butyric acid methyl ester (PC 61 BM/PC 71 BM), PSCs based on the n-OS acceptors have shown great potential in device performance and device stability. [30][31][32][33][34][35][36][37][38][39][40][41][42] The rational design of the n-OS acceptors is typically based on molecular packing and orbital energetics strategies that are utilized to effectively alter the extension of π conjugation and frontier orbital energy levels. [30][31][32][33][34][35][36][37][38][39][40][41][42] The rational design of the n-OS acceptors is typically based on molecular packing and orbital energetics strategies that are utilized to effectively alter the extension of π conjugation and frontier orbital energy levels.…”