Introducing Trifluoromethyl to Strengthen Hydrogen Bond for High Efficiency Organic Solar Cells

Abstract

Nowadays, the ternary strategy has become a common way to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). The intermolecular interaction between the third component and donor or acceptor plays a key role in achieving a high performance. However, hydrogen bond as a strong intermolecular interaction is rarely considered in ternary OSCs. In this work, we introduce trifluoromethyl on a newly synthesized small molecular DTBO to strength hydrogen bonds between DTBO and IEICO-4F. Due to the existence of hydrogen bonds has a strong impact on electrostatic potential (ESP) and benefits π-π stacking in the active layer, the ternary OSCs show superior charge extraction and low charge recombination. In DTBO, PTB7-Th and IEICO-4F based ternary devices, the PCE increases from 11.02 to 12.48%, and short-circuit current density (J SC) increases from 24.94 to 26.43 mA/cm 2 compared with typical binary devices. Moreover, the addition of DTBO can realize an energy transfer from DTBO to PTB7-Th and broaden the absorption spectrum of blend films. Grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns show that the π-π stacking distance of IEICO-4F decreased after adding 10 wt% DTBO. The effect of the hydrogen bond is also achieved in the PM6: Y6 system, showing 16.64% efficiency by comparison to the 15.49% efficiency of binary system. This work demonstrates that introduce trifluoromethyl to enhance hydrogen bond which improve π-π stacking can achieve higher performance in OSCs.

Hydrogen‐Bond‐Assisted Exciplex Emitters Realizing Improved Efficiencies and Stabilities in Organic Light Emitting Diodes

“…The below-zero values of all binding energies indicate that the formations of four intermolecular HBs can further stabilize the exciplex systems. [34,37] Meanwhile, the binding energies in 13PXB:B4PyMPM are correspondingly lower than those in 13PXZB:B3PyMPM, which suggests 13PXB:B4PyMPM mixture will have more intermolecular HBs. Moreover, based on two different binding energies of intermolecular HBs between two B4PyMPM molecules (−4.97 kcal mol −1 ) and between 13PXZB and B4PyMPM (−4.10 kcal mol −1 ), the relative ratios of two intermolecular HBs in 13PXB:B4PyMPM can be estimated by Boltzmann distribution as described below: [38] % Hydrogen Bond…”

“…The enhancements of the shorter-wavelength peaks suggest the formations of intermolecular HBs between 13PXZB and B4PyMPM and 13PXZB and B3PyMPM. [33,34] As HB is the electrostatic interaction essentially, [35,36] the molecular electrostatic potentials (ESPs) of 13PXZB, B4PyMPM, B3PyMPM, and B2PyMPM were then calculated based on their ground-state geometries by density functional theory (DFT) with the B3LYP/6-31G (d,p) basis set. And the ESP distributions of four molecules are illustrated in Figure 4.…”

High‐Performance Ternary Polymer Solar Cells Enabled by a New Narrow Bandgap Nonfullerene Small Molecule Acceptor with a Higher LUMO Level

“…[55] 3-(diethylamino)-7-imino-7Hbenzo [4,5]imidazo [1,2a]chromeno[3,2-c]pyridine-6-carbonitrile (DIBC) and 7-(dibutylamino)-3-(6-(trifluoromethyl)-1H-benzo[d] imidazol-2-yl)-2H-chromen-2-one (DTBO) both employed hydrogen bonding with IEICO-4F, which enabled to improve molecular crystallization, stacking and spatial distribution and prolong storage time [56] or impact on electrostatic potential and π-π packing of active blend, resulting in superior charge extraction and low charge recombination. [57] In this communication, we based on the PTB7-Th:IEICO-4F and report a different ternary strategy to achieve the simultaneously enhancement of the solar cell performance. The strategy is achieved by designing a new acceptor guest with a higher-LUMO level than IEICO-4F and again decorated with alkylthiophenyl side chains.…”

“…[ 55 ] 3‐(diethylamino)‐7‐imino‐7H‐benzo[4,5]imidazo[1,2a]chromeno[3,2‐c]pyridine‐6‐carbonitrile (DIBC) and 7‐(dibutylamino)‐3‐(6‐(trifluoromethyl)‐1H‐benzo[d]imidazol‐2‐yl)‐2H‐chromen‐2‐one (DTBO) both employed hydrogen bonding with IEICO‐4F, which enabled to improve molecular crystallization, stacking and spatial distribution and prolong storage time [ 56 ] or impact on electrostatic potential and π–π packing of active blend, resulting in superior charge extraction and low charge recombination. [ 57 ]…”

Synthesizing alkynyl-decorated 2D conjugated nonfullerene acceptors for efficient polymer solar cells

“…[28][29][30] Again, based on the optimized binary PSCs, the ternary strategy of employing an appropriate third component is another promising method to boost the device efficacy. [31][32][33][34][35][36] First, the photocurrent can be increased by using two absorption-complementary molecules (between donor and acceptor or two donors/acceptors) [37][38][39] as one of the ternary strategies. The use of solar photons absorbed by the third component, such as via the energy transfer channel 40,41 in combination with the improvement in film-morphology, can lead to simultaneous enhancement of short-circuit current-density ( J SC ) and fill factor (FF) or open-circuit voltage (V OC ).…”