Large-scale fabrication of organic solar cells requires an active layer with high thickness tolerability and the use of environment-friendly solvents. Thick films with high-performance can be achieved via a ternary strategy studied herein. The ternary system consists of one polymer donor, one small molecule donor, and one fullerene acceptor. The small molecule enhances the crystallinity and face-on orientation of the active layer, leading to improved thickness tolerability compared with that of a polymer-fullerene binary system. An active layer with 270 nm thickness exhibits an average power conversion efficiency (PCE) of 10.78%, while the PCE is less than 8% with such thick film for binary system. Furthermore, large-area devices are successfully fabricated using polyethylene terephthalate (PET)/Silver gride or indium tin oxide (ITO)-based transparent flexible substrates. The product shows a high PCE of 8.28% with an area of 1.25 cm for a single cell and 5.18% for a 20 cm module. This study demonstrates that ternary organic solar cells exhibit great potential for large-scale fabrication and future applications.
The open‐circuit voltage (Voc) of perovskite solar cells is limited by non‐radiative recombination at perovskite/carrier transport layer (CTL) interfaces. 2D perovskite post‐treatments offer a means to passivate the top interface; whereas, accessing and passivating the buried interface underneath the perovskite film requires new material synthesis strategies. It is posited that perovskite ink containing species that bind strongly to substrates can spontaneously form a passivating layer with the bottom CTL. The concept using organic spacer cations with rich NH2 groups is implemented, where readily available hydrogens have large binding affinity to under‐coordinated oxygens on the metal oxide substrate surface, inducing preferential crystallization of a thin 2D layer at the buried interface. The passivation effect of this 2D layer is examined using steady‐state and time‐resolved photoluminescence spectroscopy: the 2D interlayer suppresses non‐radiative recombination at the buried perovskite/CTL interface, leading to a 72% reduction in surface recombination velocity. This strategy enables a 65 mV increase in Voc for NiOx based p–i–n devices, and a 100 mV increase in Voc for SnO2‐based n–i–p devices. Inverted solar cells with 20.1% power conversion efficiency (PCE) for 1.70 eV and 22.9% PCE for 1.55 eV bandgap perovskites are demonstrated.
Light-emitting diodes (LEDs) based on metal halide perovskite quantum
dots (QDs) have achieved impressive external quantum efficiencies;
however, the lack of surface protection of QDs, combined with efficiency
droop, decreases device operating lifetime at brightnesses of interest.
The epitaxial incorporation of QDs within a semiconducting shell provides
surface passivation and exciton confinement. Achieving this goal in
the case of perovskite QDs remains an unsolved challenge in view of
the materials’ chemical instability. Here, we report perovskite
QDs that remain stable in a thin layer of precursor solution of perovskite,
and we use strained QDs as nucleation centers to drive the homogeneous
crystallization of a perovskite matrix. Type-I band alignment ensures
that the QDs are charge acceptors and radiative emitters. The new
materials show suppressed Auger bi-excition recombination and bright
luminescence at high excitation (600 W cm–2), whereas
control materials exhibit severe bleaching. Primary red LEDs based
on the new materials show an external quantum efficiency of 18%, and
these retain high performance to brightnesses exceeding 4700 cd m–2. The new materials enable LEDs having an operating
half-life of 2400 h at an initial luminance of 100 cd m–2, representing a 100-fold enhancement relative to the best primary
red perovskite LEDs.
The epitaxial growth of a perovskite
matrix on quantum dots (QDs)
has enabled the emergence of efficient red light-emitting diodes (LEDs)
because it unites efficient charge transport with strong surface passivation.
However, the synthesis of wide-band gap (E
g) QD-in-matrix heterostructures has so far remained elusive in the
case of sky-blue LEDs. Here, we developed CsPbBr3 QD-in-perovskite
matrix solids that enable high luminescent efficiency and spectral
stability with an optical E
g of over 2.6
eV. We screened alloy candidates that modulate the perovskite E
g and allow heteroepitaxy, seeking to implement
lattice-matched type-I band alignment. Specifically, we introduced
a CsPb1–x
Sr
x
Br3 matrix, in which alloying with Sr2+ increased the E
g of the perovskite and
minimized lattice mismatch. We then developed an approach to passivation
that would overcome the hygroscopic nature of Sr2+. We
found that bis(4-fluorophenyl)phenylphosphine oxide
strongly coordinates with Sr2+ and provides steric hindrance
to block H2O, a finding obtained by combining molecular
dynamics simulations with experimental results. The resulting QD-in-matrix
solids exhibit enhanced air- and photo-stability with efficient charge
transport from the matrix to the QDs. LEDs made from this material
exhibit an external quantum efficiency of 13.8% and a brightness exceeding
6000 cd m–2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.