Perovskite solar cells have reached a power conversion efficiency over 25%, and the engineering of the interface between the perovskite and hole transport layer (HTL) has been crucial to achieve high performance. Here we design a bifunctional molecule CBz-PAI with carbazole-triphenylamine and phenylammonium iodide units to passivate defects at the perovskite/HTL interface. Owing to a favourable energy level alignment with the perovskite, the CBz-PAI acts as a hole shuttle between the perovskite layer and the HTL. This minimizes the difference between the quasi-Fermi level splitting of the perovskite, or ‘internal’ Voc, and the external device Voc, thus reducing voltage losses. As a result, solar cells incorporating CBz-PAI reach a stabilized power conversion efficiency of 24.7% and maintain 92.3% of the initial efficiency after 1,000 h under damp heat test (85 °C and 85% relative humidity) and 94.6% after 1,100 h under maximum power point-tracking conditions.
Since the first isolation of 1,3,5,7-tetra-tert-butyl-s-indacene in 1986, core-expanded s- and as-indacenes have attracted intensive
interest. However, there is no reported synthesis of such type of
molecules due to their high reactivity for over 30 years. Herein,
we report the successful synthesis of two relatively stable, core-expanded
indacene isomers, dicyclopenta[b,g]-naphthalene (5) and dicyclopenta[a,f]naphthalene (6). X-ray crystallographic analyses reveal that the backbone
of 5 adopts a bond-delocalized structure, while that
of 6 exhibits a bond-localized character. Variable-temperature 1H NMR/ESR measurements, electronic absorption spectra, and
theoretical calculations confirm that both molecules are globally
antiaromatic and have an open-shell singlet ground state. However, 6 shows stronger antiaromaticity, a larger diradical character
(y
0 = 48%), and a smaller singlet–triplet
energy gap (ΔE
S‑T = −0.99
kcal mol–1) compared to 5 (y
0 = 30%, ΔE
S‑T = −6.88 kcal mol–1), which can be explained
by their different quinoidal structures.
Developing hole-transporting materials
(HTMs) with appropriate
molecular configuration and charge mobility is important to improve
perovskite solar cell (PSC) photovoltaic performance and their feasibility
for commercialization. In this work, a novel pyramidal-shaped low-cost
HTM coded MeOTTVT is prepared through extension of π-conjugation
based on a triphenylamine core. Carbon–carbon double bonds
are introduced between the core and p-methoxyl triphenylamine
to improve the planarity of the HTM, favoring intermolecular stacking
of MeOTTVT and thus improving the hole mobility of the corresponding
hole-transporting layer (HTL). The p-methoxyl
triphenylamine-endowed HTM benefits from a highest occupied molecular
orbital level well-aligned with the perovskite active layer, facilitating
effective hole extraction. The champion PSC using an MeOTTVT-based
dopant additive-free HTL yielded a power conversion efficiency (PCE)
up to 21.30%, which is considered one of the best-performing PSCs
employing a dopant additive-free small molecule HTM. In addition,
the MeOTTVT-based dopant additive-free HTL exhibits outstanding thermal
stability and high glass-transition temperature (T
g = 137.1 °C), combined with a more hydrophobic surface;
PSCs based on an MeOTTVT dopant additive-free HTL exhibit outstanding
stability against moisture, 1 sun illumination, and thermal stress.
The kinetics of sulfite oxidation in the magnesium-based wet flue gas desulfurization (FGD) process were investigated in a stirred bubbling reactor by varying the concentrations of MgSO 3 and MgSO 4 , pH, air flow and temperature. The reaction was found to be 0.88 order with respect to magnesium sulfite and the oxidation could reach the maximum rate when the pH value was close to 6.5. The mechanism of the oxidation was discussed, and it was concluded that the oxidation is controlled by diffusion of oxygen. These results would be useful for the design or process optimization of the magnesium-based wet FGD system.
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