Silaindacenodithiophene‐Based Fused‐Ring Non‐Fullerene Electron Acceptor for Efficient Polymer Solar Cells

Abstract

In this work, a new A‐D‐A type nonfullerene small molecular acceptor SiIDT‐IC, with a fused‐ring silaindacenodithiophene (SiIDT) as D unit and 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile (INCN) as the end A unit, was design and synthesized. The SiIDT‐IC film shows absorption peak and edge at 695 and 733 nm, respectively. The HOMO and LUMO of SiIDT‐IC are of −5.47 and −3.78 eV, respectively. Compared with carbon‐bridging, the Si‐bridging can result in an upper‐lying LUMO level of an acceptor, which is benefit to achieve a higher open‐circuit voltage in polymer solar cells (PSCs). Complementary absorption and suitable energy level alignment between SiIDT‐IC and wide bandgap polymer donor PBDB‐T were found. For the PBDB‐T:SiIDT‐IC based inverted PSCs, a D/A ratio of 1: 1 was optimal to achieve a power conversion efficiency (PCE) of 7.27%. With thermal annealing (TA) of the blend film, a higher PCE of 8.16% could be realized due to increasing of both short‐circuit current density and fill factor. After the TA treatment, hole and electron mobilities were elevated to 3.42 × 10−4 and 1.02 × 10−4 cm2·V−1·s−1, respectively. The results suggest that the SiIDT, a Si‐bridged fused ring, is a valuable D unit to construct efficient nonfullerene acceptors for PSCs.

Binary Nonchlorinated and Nonaromatic Solvent-Processed PTB7:PC71BM and PTB7-Th:PC71BM Active Layers Showing Efficiency Comparable to that of Chlorobenzene in Organic Solar Cells

“…The inverted devices were fabricated as ITO/ZnO/PFN/polymer:PC 71 BM (1:1.5)/MoO 3 /Al. The bi-interlayer of ZnO/PFN on the ITO cathode has been reported before . The optimal ratios of 1:1.5 for both PTB7:PC 71 BM and PTB7-Th:PC 71 BM active layers have been reported previously .…”

“…The bi-interlayer of ZnO/PFN on the ITO cathode has been reported before. 37 The optimal ratios of 1:1.5 for both PTB7:PC 71 BM and PTB7-Th:PC 71 BM active layers have been reported previously. 8 1,8-Diiodooctane (DIO) is a necessary solvent additive in the processing of PTB7:PC 71 BM and PTB7-Th:PC 71 BM active layers.…”

Small-Molecule Electron Acceptors for Efficient Non-fullerene Organic Solar Cells

“…Introduction of Si atom can result in a high-lying LUMO energy level to achieve a high V oc . When blended with PBDB-T, the devices delivered a PCE of 8.16% with high V oc of 0.92 V, but the performance is lower than the corresponding C-bridge acceptor (8.83%) due to inferior J sc (Nian et al, 2018 ). Most of the reported NFAs are trans-arranged side chains linked with the central core.…”

Silicon and Oxygen Synergistic Effects for Discovery of New High-Performance Nonfullerene Acceptors

“…Taking the advantages of silicon and oxygen atom-doping in the design of the high performance organic semiconductors, development of 6-membered silicon-oxygen-bridged (SiO-bridged) π-conjugated skeletons to investigate the synergistic effects of Si and O atoms in organic electronics is highly appealing and would significantly enhance the structural diversity of π-conjugated materials and improve the performance in a wide range of optoelectronic technologies. However, even diverse 5-membered siliconbridged π-systems such as siloles, dibenzosiloles, dithienosiloles and related compounds have been synthesized and widely utilized in organic electronics (Figure 1b) [32][33][34][35][36][37][38][39][40][41][42][43] , until now, investigations on 6membered SiO-bridged π-conjugated materials are inherently limited with the narrow structural diversity, presumably mainly because of the challenges in their synthesis.…”