The photophysical properties of films
of organic–inorganic lead halide perovskites under different
ambient conditions are herein reported. We demonstrate that their
luminescent properties are determined by the interplay between photoinduced
activation and darkening processes, which strongly depend on the atmosphere
surrounding the samples. We have isolated oxygen and moisture as the
key elements in each process, activation and darkening, both of which
involve the interaction with photogenerated carriers. These findings
show that environmental factors play a key role in the performance
of lead halide perovskites as efficient luminescent materials.
Hybrid organic-inorganic perovskite materials have risen up as leading components for light-harvesting applications. However, to date many questions are still open concerning the operation of perovskite solar cells (PSCs). A systematic analysis of the interplay among structural features, optoelectronic performance, and ionic movement behavior for FA0.83 MA0.17 Pb(I0.83 Br0.17 )3 PSCs is presented, which yield high power conversion efficiencies up to 20.8%.
Understanding the fundamental properties of buried interfaces in perovskite photovoltaics is of paramount importance to the enhancement of device efficiency and stability. Nevertheless, accessing buried interfaces poses a sizeable challenge because of their non‐exposed feature. Herein, the mystery of the buried interface in full device stacks is deciphered by combining advanced in situ spectroscopy techniques with a facile lift‐off strategy. By establishing the microstructure–property relations, the basic losses at the contact interfaces are systematically presented, and it is found that the buried interface losses induced by both the sub‐microscale extended imperfections and lead‐halide inhomogeneities are major roadblocks toward improvement of device performance. The losses can be considerably mitigated by the use of a passivation‐molecule‐assisted microstructural reconstruction, which unlocks the full potential for improving device performance. The findings open a new avenue to understanding performance losses and thus the design of new passivation strategies to remove imperfections at the top surfaces and buried interfaces of perovskite photovoltaics, resulting in substantial enhancement in device performance.
The performance of perovskite solar
cells has been progressing
over the past few years and efficiency is likely to continue to increase.
However, a negative aspect for the integration of perovskite solar
cells in the built environment is that the color gamut available in
these materials is very limited and does not cover the green-to-blue
region of the visible spectrum, which has been a big selling point
for organic photovoltaics. Here, we integrate a porous photonic crystal
(PC) scaffold within the photoactive layer of an opaque perovskite
solar cell following a bottom-up approach employing inexpensive and
scalable liquid processing techniques. The photovoltaic devices presented
herein show high efficiency with tunable color across the visible
spectrum. This now imbues the perovskite solar cells with highly desirable
properties for cladding in the built environment and encourages design
of sustainable colorful buildings and iridescent electric vehicles
as future power generation sources.
Herein we present a combined study of the evolution of both the photoluminescence (PL) and the surface chemical structure of organic metal halide perovskites as the environmental oxygen pressure rises from ultrahigh vacuum up to a few thousandths of an atmosphere. Analyzing the changes occurring at the semiconductor surface upon photoexcitation under a controlled oxygen atmosphere in an X-ray photoelectron spectroscopy (XPS) chamber, we can rationalize the rich variety of photophysical phenomena observed and provide a plausible explanation for light-induced ion migration, one of the most conspicuous and debated concomitant effects detected during photoexcitation. We find direct evidence of the formation of a superficial layer of negatively charged oxygen species capable of repelling the halide anions away from the surface and toward the bulk. The reported PL transient dynamics, the partial recovery of the initial state when photoexcitation stops, and the eventual degradation after intense exposure times can thus be rationalized.
Perovskite solar cells carry the banner for emerging photovoltaics since they have demonstrated power conversion efficiency values well above 20%, which were traditionally only accessible for fairly established technologies such as silicon. Indeed, ABX 3 perovskite materials have revolutionized solar cells due to their ease of processing and outstanding electronic and optical properties, which make them ideal candidates for the development of multi-junction devices aiming to surpass limits associated to stand-alone technologies. In this review we discuss the latest regarding this matter. First, we introduce standard materials and processing techniques involved in the preparation of state-of-the-art perovskite solar cells. We then discuss the development of perovskite-based tandem devices in which ABX 3 perovskite acts as the active material in the top subcell and Si, CIGS, polymer, or ABX 3 act as bottom subcells. Finally, we provide the reader with a discussion on the different lines of research that this rapidly developing field may follow.
Perovskite
nanoplatelets (NPls) hold promise for light-emitting
applications, having achieved photoluminescence quantum efficiencies
approaching unity in the blue wavelength range, where other metal-halide
perovskites have typically been ineffective. However, the external
quantum efficiencies (EQEs) of blue-emitting NPl light-emitting diodes
(LEDs) have reached only 0.12%. In this work, we show that NPl LEDs
are primarily limited by a poor electronic interface between the emitter
and hole injector. We show that the NPls have remarkably deep ionization
potentials (≥6.5 eV), leading to large barriers for hole injection,
as well as substantial nonradiative decay at the NPl/hole-injector
interface. We find that an effective way to reduce these nonradiative
losses is by using poly(triarylamine) interlayers, which lead to an
increase in the EQE of the blue (464 nm emission wavelength) and
sky-blue (489 nm emission wavelength) LEDs to 0.3% and 0.55%, respectively.
Our work also identifies the key challenges for further efficiency
increases.
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