With
metal halide perovskite solar cells (PSCs) now reaching device
efficiencies >23%, more emphasis must now shift toward addressing
their device stability. Recently, a triarylamine-based organic hole-transport
material (HTM) doped with its oxidized salt analogue (EH44/EH44-ox)
led to unencapsulated PSCs with high stability in ambient conditions.
Here we report criteria for triarylamine-based organic HTMs formulated
with stable oxidized salts as hole-transport layer (HTL) for increased
PSC thermal stability. The triarylamine-based dopants must contain
at least two para-electron-donating groups for radical
cation stabilization to prevent impurity formation that leads to reduced
PSC performance. The stability of unencapsulated devices prepared
using these new HTMs stressed under constant load and illumination
far outperforms that of both EH44/EH44-ox and Li+-doped spiro-OMeTAD
controls at 50 °C. Furthermore, the ability to mix and match
these dopants with a nonidentical small-molecule-based HTL matrix
broadens the design scope for highly stable and cost-effective PSCs
without sacrificing performance.
Organic transistors are key elements for flexible, wearable, and biocompatible logic applications. Multiresponsivity is highly sought‐after in organic electronics to enable sophisticated operations and functions. Such a challenge can be pursued by integrating more components in a single device, each one responding to a specific external stimulus. Here, the first multiresponsive organic device based on a photochromic–ferroelectric organic field‐effect transistor, which is capable of operating as nonvolatile memory with 11 bit memory storage capacity in a single device, is reported. The memory elements can be written and erased independently by means of light or an electric field, with accurate control over the readout signal, excellent repeatability, fast response, and high retention time. Such a proof of concept paves the way toward enhanced functional complexity in optoelectronics via the interfacing of multiple components in a single device, in a fully integrated low‐cost technology compatible with flexible substrates.
Standard layer-by-layer
solution processing methods constrain lead–halide
perovskite device architectures. The layer below the perovskite must
be robust to the strong organic solvents used to form the perovskite
while the layer above has a limited thermal budget and must be processed
in nonpolar solvents to prevent perovskite degradation. To circumvent
these limitations, we developed a procedure where two transparent
conductive oxide/transport material/perovskite half stacks are independently
fabricated and then laminated together at the perovskite/perovskite
interface. Using ultraviolet–visible absorption spectroscopy,
external quantum efficiency, X-ray diffraction, and time-resolved
photoluminesence spectroscopy, we show that this procedure improves
photovoltaic
properties of the perovskite layer. Applying this procedure, semitransparent
devices employing two high-temperature oxide transport layers were
fabricated, which realized an average efficiency of 9.6% (maximum:
10.6%) despite series resistance limitations from the substrate design.
Overall, the developed lamination procedure curtails processing constraints,
enables new device designs, and affords new opportunities for optimization.
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