Search

Two polymerized naphthalimide derivatives, named as N‐TBHOB and N‐DBH, are prepared by quaternization. They exhibit excellent performance as electron‐transport layers (ETLs) in inverted organic solar cells (i‐OSCs). The results indicate N‐TBHOB with a reticulated structure owns a superior performance on electron extraction, electron transport, thickness tolerance, and less carrier recombination compared with N‐DBH with linear structure. The i‐OSCs based on N‐TBHOB with PTB7‐Th:PC71BM as the active layer achieve power conversion efficiencies (PCEs) of 10.72% and 10.03% under the thickness of 11 and 48 nm respectively, which indicates N‐TBHOB possesses better thickness tolerance than most of organic ETLs in i‐OSCs. N‐TBHOB also shows more competent performance than N‐DBH and ZnO in nonfullerene i‐OSCs for comprehensively improved Jsc, Voc, and fill factor (FF) values. Its i‐OSC with PM6:Y6 blend presents a high PCE of 16.78%. The study provides an efficient strategy to prepare ETLs by combining conjugated and nonconjugated units with a reticulated structure in the backbone for high‐performance i‐OSCs. [ABSTRACT FROM AUTHOR]

A trilobal non-fullerene electron acceptor, BTT-3PDI , incorporating benzo[1,2- b :3,4- b ′:5,6- b ″]trithiophene (BTT) as the core and three bay-substituted perylenediimides (PDIs) as the arms, was designed and synthetized. It shows a high electron mobility of 3.69 × 10 −3 cm 2 V −1 s −1 because it is a crystalline semiconductor for the partially conjugated structure between PDI units and BTT core. BTT-3PDI shows a matched energy levels and a complementary absorption spectrum with PTB7-Th. The conventional polymer solar cells were fabricated without any processing additive or posttreatment. It showed a power conversion efficiency (PCE) of 1.35% because the unconspicuous microphase separation of the blend film leads to low electron mobility (1.67 × 10 −5 cm 2 V −1 s −1 ) and hole mobility (2.80 × 10 −5 cm 2 V −1 s −1 ). The study provides a proof that the crystalline PDI derivative with small dihedral angles between a core and PDI units can also avoid serious molecular aggregation and large phase separation in the active layer. [ABSTRACT FROM AUTHOR]

Benzo[1,2- b :4,5- b ']dithiophene derivatives (BDT) have been extensively utilized as electron-donating (D) units for the synthesis of polymer donor materials. However, its isomers, benzo[2,1- b :3,4- b ']dithiophene derivatives (i BDT), are rarely employed for this application. In this research, three polymer donors, namely PTz-BDT, PTz- i BDT-L, and PTz- i BDT-H, were designed and synthesized using BDT and i BDT as the D moieties, respectively. Notably, compared to PTz-BDT, the i BDT-based polymers exhibit superior solubility and more favorable aggregation properties. When combined with the non-fullerene acceptor Y6, the i BDT-based polymers exhibit a more advantageous phase morphology, tighter packing, higher charge mobilities, more balanced charge transport, and less charge recombination in the devices. Consequently, the power conversion efficiency (PCE) of the PTz- i BDT-H:Y6 PSC reaches 11.04 %, significantly surpassing those of the PSCs based on PTz-BDT (7.15 %) and the i BDT-based polymers reported in literature. This study introduces an effective approach to enhance the performance of polymeric donors by isomerizing its backbone and synchronously increasing its molecular weight. [Display omitted] • Polymeric donors were designed with benzo[2,1- b :3,4- b ']dithiophene derivatives as the D unit. • Isomerization strategy was used to tune conformation, solubility, and molecular packing of the polymer. • The PTz- i BDT-H:Y6 PSC yield a PCE of 11.04 %, outperforming the PTz-BDT:Y6 PSC (7.15 %). [ABSTRACT FROM AUTHOR]

Two A 2 -D-A 1 -D-A 2 small molecules ID-IND and ID-RHO have been designed and synthesized, in which isoindigo, thiophene-benzene-thiophene, and 1,3-indenedione or 3-ethylrhodanine are used as the central acceptor unit (A 1 ), the donor units (D) and the end-caped acceptor units (A 2 ), respectively. The effects of the end-caped acceptor units on molecular aggregation, absorption spectra, film morphology, hole mobilities and photovoltaic performance have been fully studied. The results indicate that ID-IND with 1,3-indenedione as the end-caped acceptor units possesses more regular molecular aggregation, red-shifted absorption spectrum, more appropriate microphase separation, higher hole mobility and better photovoltaic performance than ID-RHO with 3-ethylrhodanine as the end-caped acceptor units. Therefore, the ID-IND -based solar cell shows a power conversion efficiency (PCE) of 4.70% with a open-circuit voltage of 1.01 V, which is one of the highest PCE values in organic solar cells based on the small molecules with isoindigo as the central acceptor unit. [ABSTRACT FROM AUTHOR]

Two conjugated polymers PTTTz and PHTTz have been designed and synthesized by introducing s -tetrazine as electron-withdrawing moieties. Compared with PTTTz with 2-octyldodecyl-substituted tetrathiophene derivative as electron-donating moieties, PHTTz with hexyl- and 2-octyldodecyl-substituted hexathiophene derivative possesses relatively lower molecular coplanarity, larger stacking distance but more orderly molecular stacking, more red-shifted absorption, more suitable microphase separation, more efficient exciton dissociation, higher hole mobility, which lead to higher short-circuit current density (11.54 mA cm−2), fill factor (69.0%) and power conversion efficiency (PCE = 6.69%) values in PSCs. The PTTTz -based PSC shows an open circuit voltage of 1.02 V for its lower-ling HOMO energy level though the PCE of the PSC is only 5.16%. Moreover, the ternary PSC based PHTTz /PC 71 BM/ITIC exhibits a higher PCE value of 7.88% than the binary PSCs for more efficient exciton dissociation and complementary absorption spectrum in ternary blend film, which is one of the highest PCE values in s -tetrazine-based polymers. Image 1 • s -tetrazine-based polymer achieves a V OC of 1.02 V. • PHTTz shows the best photovoltaic performance in s -tetrazine-based polymers. • The effects of the chemical structure on molecular aggregation and photovoltaic properties are studied. [ABSTRACT FROM AUTHOR]