In recent years, hybrid perovskite solar cells (HPSCs) have received considerable research attention due to their impressive photovoltaic performance and low-temperature solution processing capability. However, there remain challenges related to defect passivation and enhancing the charge carrier dynamics of the perovskites, to further increase the power conversion efficiency of HPSCs. In this work, the use of a novel material, phenylhydrazinium iodide (PHAI), as an additive in MAPbI 3 perovskite for defect minimization and enhancement of the charge carrier dynamics of inverted HPSCs is reported. Incorporation of the PHAI in perovskite precursor solution facilitates controlled crystallization, higher carrier lifetime, as well as less recombination. In addition, PHAI additive treated HPSCs exhibit lower density of filled trap states (10 10 cm −2 ) in perovskite grain boundaries, higher charge carrier mobility (≈11 × 10 −4 cm 2 V −1 s), and enhanced power conversion efficiency (≈18%) that corresponds to a ≈20% improvement in comparison to the pristine devices.
Investigating the effectiveness of instructional practices provides an evidence base to inform instructional decisions. Synthesizing research studies on instructional effectiveness provides an estimate of the generalizability of effectiveness across settings, along with an exploration of factors that may moderate the impact, which cannot be achieved within individual studies. This study sought to provide a synthesis of evidence‐based instructional practices (EBIPs) particular to chemistry through meta‐analysis. Ninety‐nine studies were analyzed comprising a broader view of chemistry specific studies than past meta‐analyses. The results showed that EBIPs feature a demonstrably positive impact on students' academic performance in chemistry, although assessment topic coverage and setting size emerged as relevant moderators of impact and prevented making definitive conclusions of the relative impact of each EBIP. In examining publication bias, an asymmetric distribution of studies based on standard error (SE) and effect size was found, indicative of potential publication bias. To explore the potential impact of bias, the trim and fill method was employed resulting in a range for the overall weighted effect size from 0.29 to 0.62. The study concludes that evidence‐based instructional practices have demonstrated effectiveness even in consideration of potential publication bias, as the range of effect sizes remains positive, but highlights the continued need to publish null findings in the research literature.
Lead
(Pb)–Tin (Sn) mixed perovskites suffer from large open-circuit
voltage (V
oc) loss due to the rapid crystallization
of perovskite films, creating Sn and Pb vacancies. Such vacancies
act as defect sites expediting charge carrier recombination, thus
hampering the charge carrier dynamics and optoelectronic properties
of the perovskite film. Here, we report the passivation of these defects
using a controlled amount of 2-phenylethylazanium iodide (PEAI) in
perovskite precursor solution as a dopant to enhance the performance
of the 1.25 eV Pb–Sn low-bandgap perovskite solar cell. It
was found that the incorporation of PEAI in the perovskite precursor
not only improves the perovskite film quality and crystallinity but
also lowers the electronic disorder, thereby enhancing the open-circuit
voltage up to 0.85 V, corresponding to V
oc loss as low as 0.4 V and the power conversion efficiency up to 17.33%.
The value of V
oc loss obtained with this
strategy is among the least obtained for similar band gap Pb–Sn
low-bandgap perovskite solar cells. Furthermore, the ambient and dark
self-stability of the PEAI-treated devices were also enhanced. This
work presents a simple doping strategy to mitigate the V
oc loss of Pb–Sn mixed low-bandgap perovskite solar
cells.
Perovskites
have been unprecedented with a relatively sharp rise
in power conversion efficiency in the last decade. However, the polycrystalline
nature of the perovskite film makes it susceptible to surface and
grain boundary defects, which significantly impedes its potential
performance. Passivation of these defects has been an effective approach
to further improve the photovoltaic performance of the perovskite
solar cells. Here, we report the use of a novel hydrazine-based aromatic
iodide salt or phenyl hydrazinium iodide (PHI) for secondary post
treatment to passivate surface and grain boundary defects in triple
cation mixed halide perovskite films. In particular, the PHI post
treatment reduced current at the grain boundaries, facilitated an
electron barrier, and reduced trap state density, indicating suppression
of leakage pathways and charge recombination, thus passivating the
grain boundaries. As a result, a significant enhancement in power
conversion efficiency to 20.6% was obtained for the PHI-treated perovskite
device in comparison to a control device with 17.4%.
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