A new thieno[3,2-b]thiophene-incorporated acceptor
TTC has been developed. The TTC acceptor was installed in a haptacyclic
ladder-type core (BDCPDT) to furnish an n-type BDCPDT-TTC. The standard
PBDB-T:BDCPDT-IC device showed a PCE of 9.33% with a V
oc of 0.86 V and a J
sc of
16.56 mA/cm2. By molecular engineering of the acceptor
unit, the BDCPDT-TTC:PBDB-T-based device delivered an enhanced efficiency
of 10.29% with a simultaneously enhanced V
oc of 0.94 V and J
sc of 17.72 mA/cm2. Incorporation of the electron-donating thieno[3,2-b]thiophene unit into the acceptor moiety decreases the
electron-accepting strength, thereby upshifting the HOMO/LUMO energy
levels to decrease the ΔE
HOMO and E
loss, achieving a larger V
oc. Second, the extended conjugated bicyclic thieno[3,2-b]thiophene ring beneficially induces an additional optical
transition at short wavelengths, leading to improvement of J
sc. Alternatively, BDCPDT-FIC installed with
the fluorinated acceptor shows more red-shifted absorption to achieve
a high J
sc of 19.12 mA/cm2.
A new polymer PDTFDPP20 based on dithieno[3,2-b:6,7-b′]fluorene (DTF) unit was developed. This polymer with a face-on orientation has achieved a high field-effect mobility up to 5 cm2 V–1 s–1.
A formylated benzodi(cyclopentadithiophene) (BDCPDT) ladder-type structure with forced coplanarity is coupled with two 1,1-dicyanomethylene-3-indanone (IC) moieties via olefination to form a non-fullerene acceptor, BDCPDT-IC. The BDCPDT-IC, as an acceptor (A) with broad light-absorbing ability and excellent solution processability, is combined with a second PCBM acceptor (A) and a medium band gap polymer, PBDB-T, as the donor (D) to form a ternary blend with gradient HOMO/LUMO energy alignments and panchromatic absorption. The device with the inverted architecture using the D:A:A ternary blend has achieved a highest efficiency of 9.79% with a superior J of 16.84 mA cm.
High internal efficiency and high temperature stability ultraviolet (UV) light-emitting diodes (LEDs) at 308 nm were achieved using high density (2.5 × 109 cm−2) GaN/AlN quantum dots (QDs) grown by MOVPE. Photoluminescence shows the characteristic behaviors of QDs: nearly constant linewidth and emission energy, and linear dependence of the intensity with varying excitation power. More significantly, the radiative recombination was found to dominant from 15 to 300 K, with a high internal quantum efficiency of 62% even at room temperature.
A TT-terminal ladder-type donor is generally a better molecular design than the corresponding T-terminal ladder-type isomer for the development of new A–D–A NFEAs.
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