3 research outputs found
Mesoscopic Perovskite Light-Emitting Diodes
Solution-processed
hybrid bromide perovskite light-emitting-diodes (PLEDs) represent
an attractive alternative technology that would allow overcoming the
well-known severe efficiency drop in the green spectrum related to
conventional LEDs technologies. In this work, we report on the development
and characterization of PLEDs fabricated using, for the first time,
a mesostructured layout. Stability of PLEDs is a critical issue; remarkably,
mesostructured PLEDs devices tested in ambient conditions and without
encapsulation showed a lifetime well-above what previously reported
with a planar heterojunction layout. Moreover, mesostructured PLEDs
measured under full operative conditions showed a remarkably narrow
emission spectrum, even lower than what is typically obtained by nitride-
or phosphide-based green LEDs. A dynamic analysis has shown fast rise
and fall times, demonstrating the suitability of PLEDs for display
applications. Combined electrical and advanced structural analyses
(Raman, XPS depth profiling, and ToF-SIMS 3D analysis) have been performed
to elucidate the degradation mechanism, the results of which are mainly
related to the degradation of the hole-transporting material (HTM)
and to the perovskite–HTM interface
Semitransparent Perovskite Solar Cells with Ultrathin Protective Buffer Layers
Semitransparent perovskite solar cells (ST-PSCs) are
increasingly
important in a range of applications, including top cells in tandem
devices and see-through photovoltaics. Transparent conductive oxides
(TCOs) are commonly used as transparent electrodes, with sputtering
being the preferred deposition method. However, this process can damage
exposed layers, affecting the electrical performance of the devices.
In this study, an indium tin oxide (ITO) deposition process that effectively
suppresses sputtering damage was developed using a transition metal
oxides (TMOs)-based buffer layer. An ultrathin (<10 nm) layer of
evaporated vanadium oxide or molybdenum oxide was found to be effective
in protecting against sputtering damage in ST-PSCs for tandem applications,
as well as in thin perovskite-based devices for building-integrated
photovoltaics. The identification of minimal parasitic absorption,
the high work function and the analysis of oxygen vacancies denoted
that the TMO layers are suitable for use in ST-PSCs. The highest fill
factor (FF) achieved was 76%, and the efficiency (16.4%) was reduced
by less than 10% when compared with the efficiency of gold-based PSCs.
Moreover, up-scaling to 1 cm2-large area ST-PSCs with
the buffer layer was successfully demonstrated with an FF of ∼70%
and an efficiency of 15.7%. Comparing the two TMOs, the ST-PSC with
an ultrathin V2Ox layer was
slightly less efficient than that with MoOx, but its superior transmittance in the near infrared and greater
light-soaking stability (a T80 of 600
h for V2Ox compared to a T80 of 12 h for MoOx) make V2Ox a promising buffer
layer for preventing ITO sputtering damage in ST-PSCs
Graphene Interface Engineering for Perovskite Solar Modules: 12.6% Power Conversion Efficiency over 50 cm<sup>2</sup> Active Area
Interfaces between perovskite solar
cell (PSC) layer components
play a pivotal role in obtaining high-performance premium cells and
large-area modules. Graphene and related two-dimensional materials
(GRMs) can be used to “on-demand” tune the interface
properties of PSCs. We successfully used GRMs to realize large-area
(active area 50.6 cm<sup>2</sup>) perovskite-based solar modules (PSMs),
achieving a record high power conversion efficiency of 12.6%. We on-demand
modulated the photoelectrode charge dynamic by doping the mesoporous
TiO<sub>2</sub> (mTiO<sub>2</sub>) layer with graphene flakes. Moreover,
we exploited lithium-neutralized graphene oxide flakes as interlayer
at the mTiO<sub>2</sub>/perovskite interface to improve charge injection.
Notably, prolonged aging tests have shown the long-term stability
for both small- and large-area devices using graphene-doped mTiO<sub>2</sub>. Furthermore, the possibility of producing and processing
GRMs in the form of inks opens a promising route for further scale-up
and stabilization of the PSM, the gateway for the commercialization
of this technology