Most polymer donors developed so far for high-performance polymer solar cells (PSCs) are designed in planar molecular geometries containing benzodithiophene (BDT) units. In this study, three ...two-dimensional conjugated polymers, PTBF
EH
-BDD, PTBFS
DO
-BDD and PTBFS
EH
-BDD, based on thieno2,3-
f
benzofuran (TBF) building blocks with different side-chains are designed and synthesized. It is found that the TBF unit can inherit and integrate the advantages of both the BDT and benzo1,2-
b
:4,5-
b
′difuran (BDF) building blocks. Due to the synergistic effects of oxygen and sulfur in the backbone and the optimized side chain, PTBF
EH
-BDD shows a higher absorption coefficient, more suitable aggregation and improved hole mobility in comparison with PTBFS
DO
-BDD and PTBFS
EH
-BDD, which improves the
J
SC
and FF in PSCs. The PSCs based on PTBF
EH
-BDD:ITIC achieve a power conversion efficiency (PCE) of 11.13% with a
J
SC
of 17.76 mA cm
−2
, a
V
OC
of 0.893 V, and a FF of 70.16%, which is comparable with its BDT counterparts. Moreover, the PSCs based on these three TBF-based devices do not need any extra post treatments or additives. This study demonstrates that the TBF-based polymers are promising candidates for highly efficient non-fullerene PSCs.
Various two-dimensional (2D) side-chain-substituted benzo(1,2-b:4,5-b′)dithiophene (BDT) blocks have been used to construct donor polymers, whereas the size effect of the side chains on the ...photovoltaic performance was overlooked in the past few years. In this work, three size-varied conjugated spaces (benzene, naphthalene, and biphenyl) were introduced into the corresponding polymers PBDB-Ph, PBDB-Na, and PBDB-BPh. This space engineering has a significant impact on the extent of phase separation in the active layer which blended with the polymer and the acceptor ITCPTC and preserved the desired morphology. The varied space size in the side chains lead to distinct balance mobility ratios of holes to electrons (benzene, 0.21; naphthalene, 0.75; and biphenyl, 0.57). Finally, PBDB-Na-based polymer solar cells (PSCs) delivered the highest power conversion efficiency of 12.52% when compared to the PSC performances of PBDB-Ph (8.48%) and PBDB-BPh (11.35%). The method in tailoring the side chain structures could fabricate a balance between phase separation and charge transport, providing an enlightenment for the development of photovoltaic devices.
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IJS, KILJ, NUK, PNG, UL, UM
To clearly show how important the impact of side chains on organic solar cells (OSCs) is, we designed three acceptors IDIC-CxPh (x = 4, 5, or 6) via subtle side-chain regulation. Despite this small ...change, significant distinctions were detected. IDIC-C4Ph devices achieve an optimal efficiency of 13.94% under thermal annealing, but thermal-assistant solvent-vapor annealing hugely suppresses the efficiencies to 10%. However, the C6Ph side chain endows extremely disordered stacking orientations, generating moderate efficiencies of ~12.50%. Excitingly, the IDIC-C5Ph affords an unexpected two-channel π-π charge transport (TCCT) property, boosting the fill factor (FF) by up to 80.02% and efficiency to 14.56%, ranking the best among five-ring fused-ladder-type acceptors. Impressively, the special TCCT behavior of IDIC-C5Ph enables 470 nm thick-film OSC with a high FF of up to 70.12% and efficiency of 13.01%, demonstrating the great promise in fabricating large-scale OSCs.
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•OSCs are a promising technology to transform the solar energy to electricity•This article reports an efficient TCCT photovoltaic material through subtle side-chain modification•The TCCT property enables 13% efficiency with FF reaching 70% in 470 nm thick-film photovoltaics
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In recent years, nonfullerene acceptors have attracted much attention, owing to their great potential for use in high‐performance polymer solar cells.The ladder‐type building block, pyran‐bridged ...indacenodithiophene (PDT), was used for constructing A–D–A nonfullerene acceptors through introduction of oxygen atoms into an indacenodithiophene (IDT) unit. The synthesis of PDT is accomplished by a BBr3‐mediated tandem cyclization–deprotection reaction to construct the pyran ring. Hence, molecular acceptor PTIC was synthesized and used in a polymer solar cell device. Compared to the IDT‐based acceptor, PTIC exhibits higher HOMO levels and wider optical band gap at 550–800 nm. Devices fabricated with poly(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo1,2‐b:4,5‐b′dithiophene)‐co‐(1,3‐di(5‐thiophene‐2‐yl)‐5,7‐bis(2‐ethylhexyl)‐benzo1,2‐c:4,5‐c′dithiophene‐4,8‐dione) (PBDB‐T):PTIC as the active layer give a power conversion efficiency (PCE) of 7.66 %.
Single ladders (put a rung on it): The ladder‐type molecule pyran‐bridged indacenodithiophene (PDT) is used to construct a nonfullerene acceptor (PTIC) for polymer solar cells (PSCs). The central structure of PDT exhibits an ordered molecular packing in the crystal. The introduction of oxygen increases the HOMO level and expands the absorption. One such PSC device, based on PBDB‐T:PTIC, gives a power conversion efficiency of 7.66 %.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The asymmetric thienobenzodithiophene (TBD) structure is first systematically compared with the benzo1,2-b:4,5-b′dithiophene (BDT) and dithieno2,3-d:2′,3′-d′benzo1,2-b:4,5-b′dithiophene (DTBDT) ...units in donor–acceptor (D–A) copolymers and applied as the central core in small molecule acceptors (SMAs). Specific polymers including PBDT-BZ, PTBD-BZ, and PDTBDT-BZ with different macromolecular conformations are synthesized and then matched with four elaborately designed acceptor–donor–acceptor (A–D–A) SMAs with structures comparable to their donor counterparts. The resulting polymer solar cell performance trends are dramatically different from each other and highly material-dependent, and the active layer morphology is largely governed by polymer conformation. Because of its more linear backbone, the PTBD-BZ film has higher crystallinity and more ordered and denser π–π stacking than those of the PBDT-BZ and PDTBDT-BZ films. Thus, PTBD-BZ shows excellent compatibility with and strong independence on the SMAs with varied structures, and PTBD-BZ-based cells deliver high power conversion efficiency (PCE) of 10–12.5%, whereas low PCE is obtained by cells based on PDTBDT-BZ because of its zigzag conformation. Overall, this study reveals control of molecular conformation as a useful approach to modulate the photovoltaic properties of conjugated polymers.
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Ternary strategy is a promising approach to broaden the photoresponse of polymer solar cells (PSCs) by adopting combinatory photoactive blends. However, it could lead to a more complicated situation ...in manipulating the bulk morphology. Achieving an ideal morphology that enhances the charge transport and light absorption simultaneously is an essential avenue to promote the device performance. Herein, two polymers with different lengths of side groups (P1 is based on phenyl side group and P2 is based on biphenyl side group) are adopted in the dual‐acceptor ternary systems to evaluate the relationship between conjugated side group and crystalline behavior in the ternary system. The P1 ternary system delivers a greatly improved power conversion efficiency (PCE) of 13.06%, which could be attributed to the intense and broad photoresponse and improved charge transport originating from the improved crystallinity. Inversely, the P2 ternary device only exhibits a poor PCE of 8.97%, where the decreased device performance could mainly be ascribed to the disturbed molecular stacking of the components originating from the overlong conjugated side group. The results demonstrate a conjugated side group could greatly determine the device performance by tuning the crystallinity of components in ternary systems.
Side group effect in ternary polymer solar cells is studied by adopting polymers with different side groups. With appropriate side group modification, high power conversion efficiency (PCE) over 13% is realized, which could mainly be attributed to the broadened photoresponse and optimized molecular stacking. The results demonstrate that side group plays a crucial role in determining the molecular stacking of ternary heterojunction.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
To investigate the influence of fluoride phenyl side-chains onto a quinoxaline (Qx) unit on the photovoltaic performance of the narrow bandgap (NBG) photovoltaic polymers, herein, two novel NBG ...copolymers,
and
, were synthesized and characterized. 2-ethylhexylthiothiophene-substituted benzodithiophene (BDTT), 2,3-diphenylquinoxaline (DQx) or 2,3-bis(3-fluorophenyl)quinoxaline (DmFQx) and 2-ethylhexylthiophene (T) were used as the electron donor (D) unit, electron-withdrawing acceptor (A) unit and π-bridge, respectively. Compared to non-fluorine substituted
, fluoride
exhibited a wide UV-Vis absorption spectrum and high hole mobility. An enhanced short-circuit current (
) and fill factor (FF) simultaneously gave rise to favorable efficiencies in the polymer/PC
BM-based polymer solar cells (PSCs). Under the illumination of AM 1.5G (100 mW cm
), a maximum power conversion efficiency (PCE) of 6.40% was achieved with an open-circuit voltage (
) of 0.87 V, a
of 12.0 mA cm
and a FF of 61.45% in
/PC
BM-based PSCs, while
-based devices also exhibited a PCE of 5.43%. The excellent results obtained demonstrate that
by fluorine atom engineering could be a promising candidate for organic photovoltaics.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Alkylthio groups are effectively utilized in molecule design to improve the performance of polymer solar cells (PSCs). In this study, two conjugated polymers, P1 and P2, were designed and synthesized ...with alkyl and alkylthio side chains substituted on thiophene as π bridges, respectively. Owing to the twist of the backbone induced by the steric hindrance of the hexyl side chains, polymer P1 shows a low power conversion efficiency (PCE) of 2.83% in PSC devices with PC71BM as acceptor and a low hole mobility of 1.85 × 10−5 cm2 V−1 s−1 in the blend film. In contrast to the steric hindrance of the alkyl side chain, the alkylthio side chain can form S⋯S non-covalent interaction with an adjacent thiophene to maintain the molecular planarity and strengthen intermolecular interaction, which is designed in polymer P2 to improve the photovoltaic performance. As a result, the P2-based devices exhibit a higher PCE of 6.15% with an open-circuit voltage (VOC) of 0.71 V, a short-circuit current (JSC) of 14.55 mA cm−2 and a fill factor (FF) of 59.5%. The hole mobility is also increased to 2.20 × 10−4 cm2 V−1 s−1. Our results demonstrate that introducing S⋯S non-covalent interaction into conjugated polymers could be a useful strategy for building high performance photovoltaic materials.
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•Two conjugated polymers P1 and P2 with alkyl and alkylthio side chains on thiophene as π bridges were synthesized.•P2 showed higher hole mobility and stronger intermolecular interaction due to forming S…S non-covalent interaction.•The optimized P2 based device exhibited higher PCE of 6.15% than P1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Two structurally similar acceptors ITIC and IT-4F with complementary absorption spectra were employed to construct high-performance ternary blend polymer solar cells (PSCs) by combining a new polymer ...donor PBTA-PS. The ternary blend solar cell exhibits an outstanding power conversion efficiency of 13.27% with an enhanced short circuit current density (
J
SC
) of 19.60 mA cm
−2
and an excellent fill factor of 74.45%, which is higher than that of PBTA-PS:ITIC (IT-4F) binary solar cells. A wide photoresponse resulting in large
J
SC
, and good miscibility and compatibility of the three components guarantee the desired morphology and molecular packing in the ternary blend film, which improved the charge transport properties. Our results demonstrated that employing structurally similar acceptors is a promising strategy to enhance the molecular packing and realize high-performance ternary solar cells.
Ternary organic solar cells (TOSCs) offer a facile and efficient approach to increase the power conversion efficiencies (PCEs). However, the critical roles that guest components play in complicated ...ternary systems remain poorly understood. Herein, two acceptors named LA1 and LA9 with differing crystallinity are investigated. The overly crystalline LA9 induces large self‐aggregates in PM6:LA9 binary system, resulting in a lower PCE (13.12%) compared to PM6:LA1 device (13.89%). Encouragingly, both acceptors are verified as efficient guest candidates into the host binary PM6:NCBDT‐4Cl (PCE = 13.48%) and afford markedly improved PCEs up to 15.39% and 15.75% in LA1 and LA9 ternary devices, respectively. Interestingly, the higher crystallinity LA9 reveals smaller interaction energies with both the host acceptor and donor PM6. Compared to LA1, the appropriate mutual interactions in the LA9 ternary system not only induces the orderly crystallinity of PM6 but also better compatibility with the host acceptor, generating further optimized molecular orientations and ternary morphology. Therefore, enhanced charge transport and minimized recombination loss are detected in LA9 ternary devices, affording the most competitive performance among Y6‐sbsent TOSCs. This work suggests that complicated intermolecular interactions should be seriously considered when fabricating state‐of‐the‐art multiple components OSCs.
The complicated interactions between the guest and host components are studied to fabricate high‐performing ternary organic solar cells (TOSCs). Notably, the LA9 ternary devices yield the most competitive efficiency, up to 15.75%, in Y6‐absent TOSCs, owing to the superior charge transport networks originating from the appropriate interactions between the guest and host components.
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