Search

In this study, we synthesized three new polymers, P1–P3, incorporating electron-donating 6,12-dihydro-6,6,12,12-tetraoctyl-indeno[1,2-b]fluorene (IF) and structural isomers of weak and strong electron-accepting 2,5-dioctyl-4,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (IFPPD) or 2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (LFPPD), or both the IFPPD and LFPPD units to study the performance of IF-based polymers on non-fullerene acceptor-based organic solar cells (NFA-OSCs). Polymer P1 exhibited absorption from 300 nm to 450 nm with an optical bandgap (Eg) of 2.39 eV, whereas P2 and P3 showed extended absorption up to 700 nm with an Egof 1.76 eV. The determined highest occupied molecular orbital/lowest occupied molecular orbital (HOMO/LUMO) levels for P1–P3 were −5.54 eV/–3.15 eV, −5.40 eV/–3.64 eV, and −5.42 eV/–3.66 eV, respectively. The NFA-OSCs fabricated using P1–P3 as the electron donor and Y6 as the electron acceptor exhibited a maximum power conversion efficiency (PCE) of 0.8%. We also utilized P1–P3 as a co-adsorber and fabricated ternary NFA-OSCs using P1–P3:PM6:Y6 blends. The performance of the ternary devices was lower than that of binary devices made from the PM6:Y6 blend. Herein, we report the preparation of IF-based polymers containing pyrrolopyrroledione derivatives for binary and ternary NFA-OSC applications. [ABSTRACT FROM AUTHOR]

A new medium bandgap polymer incorporating electron‐rich 4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b']dithiophene (BDTT) and electron‐deficient 2,3‐didodecyl‐6,7‐difluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline (2TffQ) units in an alternate manner, namely P(BDTT‐2TffQ), was prepared for organic solar cell (OSC) applications. The optical and electrochemical properties of P(BDTT‐2TffQ) were found to be suitable to use it as an electron donor in OSCs. The absorption band covers the region from 300 to 600 nm with an optical bandgap (Eg) of 1.84 eV, and it highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) were found to be positioned at −5.36 and − 3.52 eV. The OSCs prepared by using P(BDTT‐2TffQ):[6,6]‐Phenyl‐C71‐butyric acid methyl ester (PC70BM) and P(BDTT‐2TffQ):2,2′‐((2Z,2'Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (Y6) blends provided a maximum power conversion efficiency (PCE) of 5.50% and 11.65%, respectively. The differences in the photovoltaic performances of OSCs are mainly attributed to their dissimilar short‐circuit current (Jsc), which depends on their absorption spectrum. Herein, we also compared the properties of P(BDTT‐2TffQ) with a structurally similar polymer, namely P(BDTT‐2TfQ), made up of BDTT and 2,3‐didodecyl‐6‐fluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline (2TfQ) units, for better understanding the effects of the incorporation of additional fluorine atom on the backbone of quinoxaline‐based polymers. [ABSTRACT FROM AUTHOR]

Here, we studied the potential of 2,3‐didodecyl‐6‐fluoroquinoxaline–based polymer as an electron‐donor in binary and ternary organic solar cell (OSC) applications. A new wide bandgap polymeric donor, namely poly(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐2,3‐didodecyl‐6‐fluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline) (P(BDTT‐TfQT)), is prepared. Polymer P(BDTT‐TfQT) showed intense absorption between 300 and 650 nm with an optical band gap of 1.83 eV. The determined highest occupied and lowest unoccupied molecular orbitals (highest occupied molecular orbital/lowest unoccupied molecular orbital = −5.28 eV/−3.45 eV) for P(BDTT‐TfQT) are found to be suitable to utilize as an electron donor along with widely used fullerene and non‐fullerene acceptors. The OSCs prepared by using P(BDTT‐TfQT):fullerene blend gave a maximum power conversion efficiency (PCE) of 4.64%, and the PCE further increased to 6.77% by using a non‐fullerene acceptor instead of fullerene. Overall, the improved light absorption results in higher photo‐current and PCE for P(BDTT‐TfQT):non‐fullerene blend compared to that of P(BDTT‐TfQT):fullerene blend. In contrast, the inclusion of 10 vol% of P(BDTT‐TfQT) as a third component in a high energy converting polymer: non‐fullerene blend is found to lower the performance from 16.03% to 14.50% for the resulting ternary OSCs. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate a facile technique for transforming a low‐energy‐converting quinoxaline‐based polymer into an efficient polymeric donor for non‐fullerene acceptor‐based organic solar cells (NFA‐OSCs). Alternating copolymers, namely P(BDTSi‐DTfQ), incorporating electron‐rich 4,8‐bis(triisopropylsilylethynyl)‐benzo[1,2‐b:4,5‐′]dithiophene (BDTSi) and electron‐deficient 2,3‐didodecyl‐6‐fluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline (DTfQ) units were synthesized. The properties of P(BDTSi‐DTfQ) were thoroughly studied and briefly compared to those of the reported polymers, namely P(BDTSi‐DTffQ), made up of BDTSi and 2,3‐didodecyl‐6,7‐difluoro‐5,8‐di(thiophen‐2‐yl)quinoxaline (DTffQ) units. Polymer P(BDTSi‐DTfQ) exhibited a lower bandgap (Eg) and higher highest occupied and lowest unoccupied energy levels (HOMO and LUMO) than P(BDTSi‐DTffQ). The estimated Eg and HOMO/LUMO for P(BDTSi‐DTfQ) were 1.90 eV and −5.46 eV/−3.56 eV, respectively, and for P(BDTSi‐DTffQ) the same were 1.94 eV and −5.58 eV/−3.64 eV, respectively. Interestingly, the NFA‐OSCs made from P(BDTSi‐DTfQ) as the donor and NFA, namely ITIC, as the acceptor, gave a power conversion efficiency (PCE) of 3.68%, which is much higher than the PCE obtained (⁓0.75%) for the OSCs prepared by using the P(BDTSi‐DTffQ):ITIC blend. Noticeably, the energy levels of P(BDTSi‐DTfQ) were found to be favorable for efficient charge separation when it was blended with ITIC. This blend not only allowed a better charge separation at the donor/acceptor interfaces but also significantly lowered bimolecular recombination. The overall effect was to provide a higher PCE. However, P(BDTSi‐DTffQ) showed mismatched energy levels with ITIC resulting in a higher bimolecular recombination and lower PCE. [ABSTRACT FROM AUTHOR]

Electron donor and electron acceptor materials for solution‐processable polymer solar cells (PSCs) should ideally exhibit a narrow band gap (Eg) and high solubility for improved performance. Herein, we synthesized two new near‐infrared‐absorbing alternating polymers, namely P(BTz‐FQ) and P(BTz‐DTFQ), via Stille polymerization of 4‐butoxy‐5‐(4‐butoxy‐2‐(trimethylstannyl)thiazol‐5‐yl)‐2‐(trimethylstannyl)thiazole and 5,8‐dibromo‐2,3‐didodecyl‐6,7‐difluoroquinoxaline or 5,8‐bis(5‐bromothiophen‐2‐yl)‐2,3‐didodecyl‐6,7‐difluoroquinoxaline. The absorption spectra of P(BTz‐FQ) and P(BTz‐DTFQ) ranged from 300 to 900 nm with two distinct absorption maxima at 718 and 800 nm and 665 and 718 nm, respectively. Both polymers exhibited an identical Eg of 1.41 eV, which is the lowest value reported for quinoxaline‐based polymers to date. Their highest occupied (−5.04 and −5.09 eV) and lowest unoccupied (−3.63 and −3.68 eV) molecular orbital levels were suitable for their use as electron donors along with the fullerene derivative, [6,6]‐phenyl C71 butyric acid methyl ester, as the electron acceptor in PSCs. The maximum power conversion efficiencies obtained for the PSCs utilizing P(BTz‐FQ) and P(BTz‐DTFQ) were 0.51% and 0.71%, respectively. These findings demonstrate that thiazole and fluoroquinoxaline derivatives are promising materials for PSCs and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(EH)) and 4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, Td "349 оC), slightly lower band-gap (Eg "2.10 eV) and deeper highest occupied molecular orbital energy level (HOMO "–5.36 eV) level compared to those (Td "336 оC, Eg "2.11 eV, and HOMO "–5.30 eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules. [ABSTRACT FROM AUTHOR]

We synthesized two new alternating polymers, namely P(Tt‐FQx) and P(Tt‐DFQx), incorporating electron rich tri‐thiophene and electron deficient 6‐fluoroquinoxaline or 6,7‐difluoroquinoxaline derivatives. Both polymers P(Tt‐FQx) and P(Tt‐DFQx) exhibited high thermal stabilities and the estimated 5% weight loss temperatures are 425 and 460 °C, respectively. Polymers P(Tt‐FQx) and P(Tt‐DFQx) displayed intense absorption band between 450 and 700 nm with an optical band gap (Eg) of 1.78 and 1.80 eV, respectively. The determined highest occupied/lowest unoccupied molecular orbital's (HOMO/LUMO) of P(Tt‐DFQx) (−5.48 eV/−3.68 eV) are slightly deeper than those of P(Tt‐FQx) (−5.32 eV/−3.54 eV). The polymer solar cells fabricated with a device structure of ITO/PEDOT:PSS/P(Tt‐FQx) or P(Tt‐DFQx):PC70BM (1:1.5 wt %) + 3 vol % DIO/Al offered a maximum power conversion efficiency (PCE) of 3.65% with an open‐circuit voltage (Voc) of 0.59 V, a short‐circuit current (Jsc) of 10.65 mA/cm2 and fill factor (FF) of 59% for P(Tt‐FQx)‐based device and a PCE of 4.36% with an Voc of 0.69 V, a Jsc of 9.92 mA/cm2, and FF of 63% for P(Tt‐DFQx)‐based device. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 545–552 Two new polymeric donor materials, namely P(Tt‐FQx) and P(Tt‐DFQx), comprising tri‐thiophene and mono‐ or difluoro‐substituted quinoxaline derivatives are synthesized for polymer solar cell applications. Mono‐fluoro‐substituted quinoxaline‐based polymer P(Tt‐FQx) showed more improved absorption than that of di‐fluoro‐substituted quinoxaline‐based polymer P(Tt‐DFQx), while P(Tt‐DFQx) exhibited deeper HOMO level than that of P(Tt‐FQx). Conversely, P(Tt‐FQx) offered higher photocurrent while P(Tt‐DFQx) gave higher open‐circuit voltage. Therefore, both polymers provided comparable photovoltaic performance of 3.65% and 4.36%, respectively, for the polymer solar cell devices made by using P(Tt‐FQx) or P(Tt‐DFQx):PC70BM blends. [ABSTRACT FROM AUTHOR]

In this study, two new pyrrolo[3,4-c]pyrrole-1,3-dione (PPD)-based polymers (P3 and P4) incorporating a 2-octyldodecyl (branched alkyl) group on the pyrrole nitrogen of the PPD unit were prepared. Their properties were briefly compared to those of the structurally quite similar PPD-based polymers (P1 and P2) with an n-octyl (linear alkyl) group on the PPD unit, in order to understand the importance of the pyrrole N-alkyl group. The calculated optical band gaps (Eg) and highest occupied molecular orbital energy levels of P3 and P4 were found to be around ∼0.1 eV higher and deeper, respectively, compared to those of the respective linear alkylated polymers P1 and P2. The maximum power conversion efficiency (PCE) obtained for the polymer solar cells made by using P3 or P4:PC70BM blends without any additive was around ∼2%, which was quite similar to that of the PSCs made using P1 or P2:PC70BM blends. However, P3 and P4 exhibited a notably lower PCE than that of P1 and P2, respectively, when the polymer solar cells were created with an additive. This study confirmed that the alkyl substituent on the pyrrole nitrogen of the PPD unit significantly affects the properties of the resulting polymer. [ABSTRACT FROM AUTHOR]

Two new tercopolymers (RP1 and RP2) containing electron-donating benzodithiophene, weak electron-accepting pyrrolo[3,4-c]pyrrole-1,3-dione derivative and strong electron-accepting 5,6-difluorobenzothiadiazole derivative were prepared. The opto-electrical studies showed that RP1 and RP2 displayed identical optical band gaps ( E ~ 1.72 eV) and highest occupied/lowest unoccupied molecular orbital energy levels (HOMO/LUMO ~ −5.32 eV/−3.60 eV). The polymer solar cells prepared with the configuration of ITO/PEDOT:PSS/RP1:PCBM (1:1.5 wt%) + 3 vol% DIO/Al and ITO/PEDOT:PSS/RP2:PCBM (1:1.5 wt%) + 3 vol% DIO/Al exhibited a maximum power conversion efficiency (PCE) of 5.16% ( V ~ 0.76 V, J ~ 10.93 mA/cm, and FF ~ 0.62) and a PCE of 3.56% ( V ~ 0.67 V, J ~ 9.67 mA/cm, and FF ~ 0.55), respectively. [ABSTRACT FROM AUTHOR]

A series of pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (DPPD)-based polymers incorporating different alkyl side chains on the imide nitrogen were prepared to investigate the imide-linked alkyl side chain effects on the properties of DPPD-based polymers. DPPD derivatives with heptyl, octyl, decyl and dodecyl substituents on the imide nitrogen were prepared and copolymerized with 2,6-bis(trimethyltin)-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene (BDT) to offer polymers P(BDT-C 7 -DPPD), P(BDT-C 8 -DPPD), P(BDT-C 10 -DPPD), and P(BDT-C 12 -DPPD), respectively. All four polymers displayed identical optical band gaps ( E g ∼ 2.11 eV) and highest occupied/lowest unoccupied molecular orbital energy levels (HOMO/LUMO ∼ −5.39 eV/–3.28 eV). The conventional single layer polymer solar cell (PSC) fabricated with a device structure of ITO/PEDOT:PSS/polymer:PC 70 BM (1:1.5 wt%)/Al offered a power conversion efficiency ( PCE ) of 1.65%, 1.49%, 1.24%, and 0.87%, respectively. The PSC device performance was improved to 5.67%, 5.29%, 4.06%, and 2.46%, respectively, with the use of processive additive such as 1,8-diiodoocate (DIO). [ABSTRACT FROM AUTHOR]

Two benzodithiophene (BDT)-based broad absorbing low band gap random copolymers, P1 and P2, incorporating electron accepting imide functionalized pyrrolo[3,4-c]pyrrole-1,3-dione (TDPPDT) and lactam functionalized pyrrolo[3,4-c]pyrrole-1,4-dione (DKPP) derivatives are prepared. The copolymerization of differently alkylated two TDPPDT derivatives with both of BDT and DKPP offers random copolymers P1 and P2. The absorption bands of polymers P1 and P2 cover the region from 300 to 900 nm and the estimated band gaps of P1 and P2 are 1.43 and 1.39 eV, respectively. The highest occupied molecular orbital energy levels of P1 and P2 are identical, at -5.25 eV. The organic field effect transistors made from P1 and P2 provide a hole mobility μ of 3.0 × 10−4 and 3.6 × 10−5 cm2 V−1 s−1, respectively. Polymer solar cells (PSCs) prepared from P1 and P2 afford a maximum power conversion efficiency of 1.64% and 2.14%, respectively. [ABSTRACT FROM AUTHOR]

A pyrrole-based, imide-functionalized, electron-deficient monomer unit, 4,6-dibromo-2,5-dioctylpyrrolo [3,4-c]pyrrole-1,3(2H,5H)-dione (DPPD), was copolymerized with electron-rich 2,6-bis(trimethyltin)-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene to afford the polymer P(BDT-DPPD). The weight-averaged molecular weight (Mw) of P(BDT-DPPD) was 6.41 x 10³ g/mol with a polydispersity index (PDI) of 1.32. P(BDT-DPPD) displayed a broad absorption band from 300 to 600 nm with onset absorption at 596 nm in the film state. The calculated optical bandgap of P(BDT-DPPD) was 2.08 eV, and the estimated highest occupied molecular orbital energy level of P(BDT-DPPD) was -5.48 eV. The polymer solar cell (PSC) fabricated in the ITO/PEDOT:PSS/P(BDT-DPPD)/PC70BM (1:2wt%)/Al configuration was found to give a maximum power conversion efficiency (PCE) of 1.46% with an open-circuit voltage (Voc) of 0.79 V, a current density (Jsc) of 4.59 mA/cm², and a fill factor (FF) of 40%. [ABSTRACT FROM AUTHOR]

To explore the aptitude of 1,2,4-oxadiazole-based electron-acceptor unit in polymer solar cell applications, we prepared four new polymers (P1-P4) containing 1,2,4-oxadiazole moiety in their main chain and applied them to solar cell applications. Thermal, optical, and electrochemical properties of the polymers were studied using thermogravimetric, absorption, and cyclic voltammetry analysis, respectively. All four polymers showed high thermal stability (5% degradation temperature over 335 °C), and the optical band gaps were calculated to be 2.20, 1.72, 1.37, and 1.74 eV, respectively, from the onset wavelength of the film-state absorption band. The energy levels of the polymers were found to be suitable for bulk heterojunction (BHJ) solar cell applications. The BHJ solar cells were prepared by using the synthesized polymers as a donor and PC71BM as an electron acceptor with the configuration of ITO/PEDOT:PSS/polymer:PC71BM (1:3 wt %)/LiF/Al. One of the polymers was found to show the maximum power conversion efficiency of 1.33% with a Jsc of 4.95 mA/cm2, a Voc of 0.68 V, and a FF of 40%, measured using AM 1.5 G solar simulator at 100 mW/cm2 light illumination. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

A new polymer, P(BDT-fPPD) , which incorporates 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-bʹ]dithiophene (BDT) and 4,6-bis(furan-2-yl)-2,5-dioctylpyrrolo [ 3,4-c]pyrrole-1,3(2H,5H)-dione (fPPD, furan π–bridged PPD) units, was prepared. The optoelectrical, crystalline, charge transport, backbone curvature, and photovoltaic properties of P(BDT-fPPD) were thoroughly studied. P(BDT-fPPD) was also compared to the polymer P(BDT-tPPD) , comprising BDT and 4,6-bis(thiophen-2-yl)-2,5-dioctylpyrrolo [ 3,4-c]pyrrole-1,3(2H,5H)-dione (tPPD, thiophene π–bridged PPD) units. This study demonstrates that the π–bridges, such as thiophene and furan, attached between the BDT and pyrrolo [ 3,4-c]pyrrole-1,3(2H,5H)-dione (PPD) units greatly altered the properties of the resulting polymers. In particular, the backbone curvature of P(BDT-fPPD) was significantly different from that of P(BDT-tPPD) , which resulted in P(BDT-fPPD) having a higher bandgap energy (E g), deeper HOMO level, and higher crystallinity, but lower carrier mobility (μ h) and relatively poor power conversion efficiency (PCE) compared to P(BDT-tPPD). For P(BDT-fPPD), the E g , HOMO, μ h , and PCE were determined as 2.20 eV, −5.44 eV, 1.19 × 10−5 cm−2 V−1 s−1, and 2.62%, respectively. The corresponding values for P(BDT-tPPD) were 2.11 eV, −5.39 eV, 2.95 × 10−4 cm−2 V−1 s−1 and 5.29%, respectively. Interestingly, the inclusion of a small amount of P(BDT-tPPD) in the PTB7-Th:PC 70 BM blend enhanced the PCE of the resulting ternary organic solar cells (OSCs), whereas the insertion of P(BDT-fPPD) lowered the PCE of the ternary OSCs. The lower mobility and PCE obtained for P(BDT-fPPD) are mainly attributed to its poor blending with PC 70 BM. [Display omitted] • New polymer namely P(BDT-fPPD) was prepared. • The properties of P(BDT-fPPD) and P(BDT-tPPD) were compared. • P(BDT-fPPD) and P(BDT-tPPD) showed s-type and linear curvature backbones. • P(BDT-tPPD) provided higher PCE in binary and ternary OSCs than P(BDT-fPPD). • The higher crystallinity of P(BDT-fPPD) provoked aggregation and offer low PCE. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Keto-functionalized 2,5-bis(2-thienyl)pyrrole (TPTK)-based new polymers prepared. • The opto-electrical and photovoltaic properties of new polymers elaborately studied. • The properties are compared with those of imide-functionalized (TPTI) polymers. • TPTK-polymers showed higher band-gap and lower mobility than TPTI-polymers. • TPTK-polymers showed less PCE than TPTI-polymers. Abstract A 2,5-bis(2-thienyl)pyrrole (TPT)-based new monomer unit incorporating the electron-withdrawing 1-decanone (ketone) at the 3- and 4-positions of the pyrrole unit of TPT was prepared. The resulting keto-functionalized TPT unit (≈TPTK) was polymerized with distannyl derivatives of 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2- b :4,5- b ′]dithiophene (BDTT), 4,7-bis(thiophen-2-yl)benzo[ c ][1,2,5]thiadiazole (DTBT), and 3,6-bis(thiophen-2-yl)-2,5-dioctylpyrrolo[3,4- c ]pyrrole-1,4(2H,5H)-dione (DKPP), to obtain three new polymers (P(BDTT-TPTK), P(DTBT-TPTK) and P(DKPP-TPTK)) , respectively. The photophysical, electrochemical, and energy conversion efficiency of the TPTK-based polymers were thoroughly studied and compared with those of structurally similar polymers (P(BDTT-TPTI), P(DTBT-TPTI), and P(DKPP-TPTI)) incorporating an imide-functionalized TPT unit (≈ TPTI). Overall, the TPTK-based polymers showed a higher band-gap (E g ≈ 2.42 eV, 1.92 eV, and 1.42 eV), deeper highest occupied molecular orbital (HOMO ≈ −5.58 eV, −5.48 eV, and −5.31 eV, respectively) energy levels and lower carrier mobilities than those of the corresponding TPTI-based polymers. These combined effects led to relatively poor solar to electrical energy conversion efficiency for TPTK-based polymers compared to those of TPTI-based polymers. [ABSTRACT FROM AUTHOR]

Abstract The conventional polymerization of 2,5-bis(trimethylstannyl)thiophene (T) or 2,5-bis(trimethylstannyl)thieno[3,2-b]thiophene (Tt) with 4,6-bis(5-bromothiophen-2-yl)-5-octyl-2-(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (TPPDT) afforded new alternating polymers, namely P(T-TPPDT) or P(Tt-TPPDT) , respectively. Both P(T-TPPDT) and P(Tt-TPPDT) exhibited similar thermal stabilities (5% weight loss at around 420 °C) and absorption maxima (λ max ≈ 515 nm) as films. The absorption bands of P(T-TPPDT) and P(Tt-TPPDT) extend between 300 and 620 nm, with optical band gaps (E g s) of 2.02 eV and 2.00 eV, respectively. The highest-occupied/lowest-unoccupied molecular-orbital energies of P(Tt-TPPDT) (HOMO/LUMO: −5.35 eV/–3.33 eV) were found to be somewhat higher than those of P(T-TPPDT) (HOMO/LUMO: −5.31 eV/–3.31 eV). Organic solar cells (OSCs) prepared using 1:1.5 (w/w) P(T-TPPDT) :PC 70 BM or P(Tt-TPPDT) :PC 70 BM (PC 70 BM = [6,6]-phenyl C 70 butyric acid methyl ester) blends provided power-conversion efficiencies (PCE s) of 3.50% or 4.71%, respectively. On the other hand, OSCs prepared with 1:1 (w/w) P(T-TPPDT) :ITIC or P(Tt-TPPDT) :ITIC (ITIC = 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone))-5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d:2′,3′-d']-s-indaceno[1,2-b:5,6-b']dithiophene) blends exhibited improved PCE s of 5.32% or 6.35%, respectively. Graphical abstract Image 1 Highlights • Two new polymers, P(T-TPPDT) and P(Tt-TPPDT) , were prepared. • The optical band gaps were 2.02 eV and 2.00 eV. • The HOMO/LUMO levels were −5.35 eV/‒3.33 eV and −5.31 eV/‒3.31 eV. • The polymer:PC 70 BM blends offered a PCE of 3.50% and 4.71%. • The polymer:ITIC blends provided a PCE of 5.32% and 6.35%. [ABSTRACT FROM AUTHOR]

Four ternary copolymers (RP1−4) containing electron-rich 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b’]dithiophene (BDT) and electron-deficient 4,6-bis(thiophen-2-yl)-2,5-dioctylpyrrolo[3,4-c]pyrrole-1,3-dione (DPPD) and 5-octylthieno [3,4-c]pyrrole-4,6-dione (TPD) units at a 2:1:1 ratio were prepared using four differently modified synthetic procedures to understand the effects of chain growth of the repeating units on the properties of the resulting ternary copolymer. Each copolymer showed a distinct absorption band between 350–700 nm with an optical band gap of 1.91 eV for RP1 and 1.85 eV for RP2−4. On the other hand, the highest occupied molecular orbital (HOMO) energy levels of all four copolymers were identical and the estimated HOMO level was −5.37 eV. All four copolymers, RP1−4, exhibited a hole mobility in the order of 10 −4 cm 2 V −1 s −1 . The polymer solar cells (PSCs) prepared using RP1−4 and PC 70 BM offered a maximum photovoltaic performances of 5.84%, 5.23%, 5.08%, and 4.86%, respectively. The open-circuit voltage ( V oc ) and fill factor ( FF ) of the PSC devices made from RP1−4 were similar but the short-circuit current ( J sc ) was different, which affected the photovoltaic performance. These results show that the properties of ternary copolymers are affected significantly by the diverse arrangements of two different repeating units of the ternary copolymer. [ABSTRACT FROM AUTHOR]

Three new electron rich dithienosilole (DTS)-based polymers (P1, P2 and P3) incorporating electron deficient imide-functionalized pyrrolo[3,4-c]pyrrole-1,3-dione (DPPD), lactam-functionalized pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) or both of DPPD and DPP units were prepared to study the property modulation of polymers via functional group inter-conversion in their main chain. The intense absorption of P1 incorporating DPPD covered the region, 300 nm–650 nm, with the maximum absorption at 526 nm, while P2 incorporating DPP showed a strong absorption band between 500 nm and 950 nm with the maximum absorption at 733 nm. Interestingly, P3 incorporating both of DPPD and DPP units displays broad absorption from 300 nm to 950 nm with two distinct characteristic absorption maxima at 518 nm and 731 nm. The estimated optical band gaps of P1–P3 were 1.91 eV, 1.31 eV and 1.35 eV, respectively. The highest occupied molecular orbital (HOMO) energy levels of P1–P3 are observed at −5.36 eV, −5.07 eV and −5.12 eV, respectively. An examination of the organic field effect transistors (OFETs) prepared with each of P1–P3 showed that P1 exhibits higher hole mobility (μ) of 2.7 × 10 −4 cm 2 V −1 s −1 compared to that of P2 (1.3 × 10 −4 cm 2 V −1 s −1 ) and P3 (7.0 × 10 −5 cm 2 V −1 s −1 ). The polymer soar cells (PSCs) made from each of polymers P1–P3 as a donor and PC 70 BM as an acceptor with the simple device structure of ITO/PEDOT:PSS/polymer:PC 70 BM + DIO/Al produced a maximum power conversion efficiency ( PCE ) of 3.46%, 3.60% and 0.93%, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Anthracene-based small molecules incorporating an electron accepting tricyanovinyl (TCV) group was prepared to investigate the linkage position influences of the anthracene and TCV groups on the opto-electrical and photovoltaic properties of the molecules. The maximum absorptions of the anthracene-based molecules incorporating the TCV group at the phenyl group of the triphenylamine unit (TCV-TpaA 9,10 T, TCV-TpaTA 9,10 T, and TCV-TpaA 2,6 T) or at the thiophene unit (TpaA 9,10 T-TCV, TpaTA 9,10 T-TCV, and TpaA 2,6 T-TCV) were found to be dependent on the linkage position of the anthracene unit. The HOMO energy levels of the molecules containing TCV group at the phenyl group of the triphenylamine unit were deeper than those of the molecules containing TCV group at the thiophene unit. The solution processed small molecule organic solar cells (SMOSCs) prepared with the structure of ITO/PEDOT:PSS/TCV-TpaA 9,10 T or TCV-TpaA 2,6 T or TpaA 2,6 T-TCV:PC71BM (2:1 wt %)/LiF/Al exhibited a maximum energy conversion efficiency of 1.04%, 1.67%, and 1.95%, respectively, under AM 1.5 irradiation (100 mW cm−2). [Copyright &y& Elsevier]

Three new benzodithiophene- alt -di(thiophen-2-yl)quinoxaline polymers were prepared with the aim of exploring 5,8-bis(thiophen-2-yl)-2,3-didodecyl-6,7-difluoroquinoxaline (TFQ)-based polymers on fullerene-free organic solar cells (OSCs). The electron-rich benzo[1,2-b:4,5-bʹ]dithiophene unit contains three different substituents, namely 2,6-bis(trimethyltin)-4,8-bis(2-butyloctyloxy)benzo[1,2-b:4,5-bʹ]dithiophene (Distannyl BDTO), 2,6-bis(trimethyltin)-4,8-bis(5-(2-butyloctyl)thiophen-2-yl)benzo[1,2-b:4,5-bʹ]dithiophene (Distannyl BDTT), and 2,6-bis(trimethyltin)-4,8-bis(triisopropylsilylethynyl)-benzo[1,2-b:4,5-ʹ]dithiophene (Distannyl BDTSi). These were polymerized with electron deficient 5,8-bis(5-bromothiophen-2-yl)-2,3-didodecyl-6,7-difluoroquinoxaline (Dibromo TFQ) to afford the polymers P(BDTO-TFQ) , P(BDTT-TFQ) , and P(BDTSi-TFQ). The estimated band-gaps (E g s) and the highest occupied molecular orbital levels (HOMOs) were 1.88, 1.86, and 1.94 eV, and −5.35, −5.44, and −5.58 eV, respectively. The OSCs made with a blend of polymer and ITIC (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)indanone))-5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d:2ʹ,3′-dʹ]-s-indaceno[1,2-b:5,6-bʹ]dithiophene) gave the maximum power-conversion efficiencies (PCE s) of 3.49, 7.06, and 0.75%, respectively. Overall, the substituents attached at the 4- and 8-positions of the BDT unit of the TFQ-based polymers were found to exhibit greatly altered properties, such as their absorption, energy levels, and crystallinity. This resulted in dissimilar photovoltaic performance for the resulting polymers. Image 1021 • Quinoxaline-based three new polymers with different substituents were prepared. • The calculated optical bands were 1.88 eV, 1.86 eV, and 1.94 eV, respectively. • The determined HOMO levels were −5.35 eV, −5.44 eV, and −5.58 eV, respectively. • The maximum PCEs of NFA OSCs were 3.49%, 7.06%, and 0.75%, respectively. • The substituents on the polymer backbone were greatly alter their properties. [ABSTRACT FROM AUTHOR]

A new alternating copolymer, P(BDTSi-PPD) , comprising 4,8-bis(triisopropylsilylethynyl)-benzo[1,2-b:4,5-ʹ]dithiophene (BDTSi) and 4,6-bis(thiophen-2-yl)-2,5-dioctylpyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (PPD) units was prepared. The photophysical, electrochemical, and photovoltaic properties of P(BDTSi-PPD) , as well as the backbone curvature, charge transport, and crystallinity, were studied and briefly compared with those of structurally similar high-energy-converting wide-bandgap copolymers, namely P(BDTO-PPD), containing 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-bʹ]dithiophene (BDTO) and PPD units. Polymer P(BDTSi-PPD) displayed a slightly broader absorption band, deeper highest occupied molecular orbital (HOMO), and lower π–π stacking ability compared to those of P(BDTO-PPD). Nevertheless, the poor power conversion efficiency of organic solar cells (OSCs) employing a binary blend of P(BDTSi-PPD) :PC 70 BM was inferior (PCE ∼ 1.08%) to that of devices made from the P(BDTO-PPD):PC 70 BM blend (PCE ∼ 5.42%). However, the inclusion of 3 vol% P(BDTSi-PPD) in the PTB7-Th:PC 70 BM blend significantly enhanced the PCE of the resulting ternary OSCs, where the PCE increased from 7.86% to 8.51%. In contrast, the PCE of the PTB7-Th:PC 70 BM blend increased to 8.34% with the addition of 10 vol% P(BDTO-PPD) to the primary blend. Overall, P(BDTSi-PPD) works as an additive material in OSCs, whereas P(BDTO-PPD) acts mainly as a co-absorber. This study demonstrates that replacing 2-ethylhexyloxy (EHO) with a triisopropyl(prop-1-ynyl)silane (TIPS) substituent on the backbone of benzo[1,2-b:4,5-bʹ]dithiophene (BDT) units of PPD-based polymers results in significant attenuation of the photovoltaic properties. [Display omitted] • Substituent, EHO and TIPS, effects on the properties of PPD-based polymers studied. • TIPS-substituted polymer showed lower bandgap and deeper HOMO level. • EHO-substituted polymer gave higher PCE in binary blend OSCs. • TIPS-substituted polymer gave higher PCE in ternary blend OSCs. • TIPS-substituted polymer works as both additive and co-absorbing materials. [ABSTRACT FROM AUTHOR]

Abstract: Electron rich, fused N-aryl pyrrole based monomer namely 2,6-di(4,4,5,5-tetramethyl-1,3,2-dioxaborolan)-N-[4-octylphenyl]dithieno[3,2-b:2′,3′-d]pyrrole (N-aryl DTP) was synthesized and copolymerized with electron deficient 4,7-bis(5-bromo-3-octyl-2-thienyl)-2,1,3-benzothiadiazole (TBT) to afford alternating polymer PDTPTBT. The absorption band of PDTPTBT was found to cover the entire visible part of the solar spectrum (300 nm–750 nm) and the optical band gap was estimated to be 1.62 eV. In order to extent the absorption of PDTPTBT, another strong electron acceptor unit such as 2,1,3−benzothiadiazole or dimethyl-2H-benzimidazole was incorporated in polymer main chain by copolymerizing three different comonomers (N-aryl DTP, TBT and 4,7-dibromo-2,1,3−benzothiadiazole (B) or 4,7-dibromo-2,2-dimethyl-2H-benzimidazole (BI)) at 2:1:1 ratio to afford polymers PDTPTBTB and PDTPTBTBI, respectively. The absorption band of PDTPTBTB and PDTPTBTBI was found to be extended up to 1000 nm and 1200 nm, respectively, and the optical band gap was calculated to be 1.33 eV and 1.07 eV, respectively. The HOMO-LUMO energy levels of PDTPTBT, PDTPTBTB and PDTPTBTBI were found to be suitable for polymer solar cell (PSC) applications. The single layer PSCs fabricated with the configuration of ITO/PEDOT:PSS/PDTPTBT, PDTPTBTB or PDTPTBTBI:PC60BM(1:3 wt/wt)/LiF/Al showed maximum power conversion efficiency (PCE) of 2.04%, 1.01% and 0.70%, respectively. [Copyright &y& Elsevier]

In this study, we investigate the effects of polymer backbone curvature on the performance of non-fullerene organic solar cells (NFA-OSCs) fabricated using an electron-donating π-conjugated polymer and a non-fullerene electron-acceptor (NFA), 3,9-bis[2-methylene(3-(1,1-dicyanomethylene)-indanone)]-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3- d :2ʹ,3ʹ- dʹ ]-s-indaceno[1,2 -b :5,6- bʹ ]dithiophene (ITIC). The NFA-OSCs are fabricated using structurally similar bis(pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione) (BPPD)-based π–conjugated polymers, i.e., P1 and P2, and they indicate almost identical absorption and energy levels but dissimilar backbone curvatures. P1 comprises two-dimensional conjugated benzodithiophene (BDTT) and thiophene π-bridged BPPD derivatives, and P2 comprises BDTT and thieno[3,2-b]thiophene π-bridged BPPD derivatives. The absorption maximum and highest occupied/lowest unoccupied molecular orbital levels of P1 and P2 are ~505 nm and ~˗5.4/˗3.4 eV, respectively. However, P1 shows a twisted backbone, whereas P2 exhibits a well-controlled wavy backbone owing to the presence of slightly different-structured π-bridges, such as thiophene and thieno[3,2-b]thiophene, on their backbones. The NFA-OSCs are fabricated with the structures of glass-ITO/PEDOT:PSS/P1 and P2:ITIC+0.5 vol% 1,8-diiodoctane (DIO)/PFN-Br/Al provide quite different device performances with power conversion efficiency of 0.88% and 6.25%, respectively. In general, the curvature of the polymer backbone significantly affects the nanoscale network formation between the polymer and ITIC, thereby resulting in a significant difference in the carrier transport and photovoltaic performances of the NFA-OSCs. Image 1 • Polymer backbone curvature effects on NFA-OSCs were studied. • Twisted backbone polymer offered poor PCE of 0.9%. • Controlled wavy backbone polymer provided relatively higher PCE of 6.2%. • Polymer backbone curvature affects the morphology, carrier transport, and PCE. • Controlled wavy backbone polymers are favorable to NFA-OSCs. [ABSTRACT FROM AUTHOR]

A series of novel alternating polymers, namely P(BDTO-TTFQ) , P(BDTT-TTFQ) , and P(BDTSi-TTFQ) , incorporating electron-rich benzo [1,2-b:4,5-bʹ]dithiophene (BDT) derivatives, namely 4,8-bis(2-butyloctyloxy)benzo [1,2-b:4,5-bʹ]dithiophene (BDTO), 4,8-bis(5-(2-butyloctyl)thiophen-2-yl)benzo [1,2-b:4,5-bʹ]dithiophene (BDTT), and 4,8-bis(triisopropylsilylethynyl)-benzo [1,2-b:4,5-ʹ]dithiophene (BDTSi), as well as electron-deficient 5,8-bis(5-(4-hexylthiophen-2-yl)thiophen-2-yl)-2,3-didodecyl-6,7-difluoroquinoxaline (TTFQ) units were prepared. The photo-physical, electrochemical, crystallinity, curvature, charge transport, and photovoltaic properties of the TTFQ-based polymers were investigated thoroughly and compared briefly to those of structurally similar 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (TFQ)-based polymers, namely P(BDTO-TFQ), P(BDTT-TFQ), and P(BDTSi-TFQ), containing BDTO, BDTT, and BDTSi. This study confirmed that the incorporation of additional π˗bridges (3-hxeylthiophene) between the BDT and TFQ units of P(BDTO-TFQ), P(BDTT-TFQ), and P(BDTSi-TFQ) do not significantly alter the properties of the polymers P(BDTO-TFQ) and P(BDTT-TFQ), but do significantly alter the properties of P(BDTSi-TFQ). Consequently, the polymers P(BDTO-TTFQ) and P(BDTT-TTFQ) exhibit comparable power conversion efficiencies (PCEs, 3.99% and 6.69%, respectively) to those of P(BDTO-TFQ) and P(BDTT-TFQ) (3.49% and 7.06%, respectively), but P(BDTSi-TTFQ) exhibits a significantly improved PCE of 6.21% compared to that of P(BDTSi-TFQ) (0.75%). The photovoltaic performance of quinoxaline-based polymers was greatly increased via the side and main chain engineering of the polymer backbone, and the PCE was maximum enhanced from 0.8% to 6.2%. Image 1 • Qunoxaline-based three new polymers with different substituent were prepared. • The calculated optical bands were 1.87 eV, 1.84 eV and 1.85 eV, respectively. • The determined HOMO levels were −5.24 eV, −5.36 eV and −5.48 eV, respectively. • The maximum PCEs of NFA OSCs were 3.99%, 6.69% and 6.21%. • π-bridge engineering on the polymer backbone with were greatly alter their properties. [ABSTRACT FROM AUTHOR]