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Nat Commun ; 10(1): 16, 2019 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-30604757


There has been an urgent need to eliminate toxic lead from the prevailing halide perovskite solar cells (PSCs), but the current lead-free PSCs are still plagued with the critical issues of low efficiency and poor stability. This is primarily due to their inadequate photovoltaic properties and chemical stability. Herein we demonstrate the use of the lead-free, all-inorganic cesium tin-germanium triiodide (CsSn0.5Ge0.5I3) solid-solution perovskite as the light absorber in PSCs, delivering promising efficiency of up to 7.11%. More importantly, these PSCs show very high stability, with less than 10% decay in efficiency after 500 h of continuous operation in N2 atmosphere under one-sun illumination. The key to this striking performance of these PSCs is the formation of a full-coverage, stable native-oxide layer, which fully encapsulates and passivates the perovskite surfaces. The native-oxide passivation approach reported here represents an alternate avenue for boosting the efficiency and stability of lead-free PSCs.

Angew Chem Int Ed Engl ; 55(47): 14723-14727, 2016 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-27766739


Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH4 PbI3 non-perovskite thin film converts stepwise into a dense, ultrasmooth, textured CH3 NH3 PbI3 perovskite thin film. Owing to the beneficial phase/structural development of the thin film, its photovoltaic properties undergo dramatic enhancement during this NH4 PbI3 -to-CH3 NH3 PbI3 transformation process. The chemical origins of this transformation are studied at various length scales.

Nat Commun ; 7: 12693, 2016 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-27562148


Interfaces are essential in electrochemical processes, providing a critical nanoscopic design feature for composite electrodes used in Li-ion batteries. Understanding the structure, wetting and mobility at nano-confined interfaces is important for improving the efficiency and lifetime of electrochemical devices. Here we use a Surface Forces Apparatus to quantify the initial wetting of nanometre-confined graphene, gold and mica surfaces by Li-ion battery electrolytes. Our results indicate preferential wetting of confined graphene in comparison with gold or mica surfaces because of specific interactions of the electrolyte with the graphene surface. In addition, wetting of a confined pore proceeds via a profoundly different mechanism compared with wetting of a macroscopic surface. We further reveal the existence of molecularly layered structures of the confined electrolyte. Nanoscopic confinement of less than 4-5 nm and the presence of water decrease the mobility of the electrolyte. These results suggest a lower limit for the pore diameter in nanostructured electrodes.

Chem Commun (Camb) ; 52(45): 7273-5, 2016 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-27181497


The α→δ phase transition, which occurs favorably in planar films of a black α-HC(NH2)2PbI3 (α-FAPbI3) perovskite in the amibent, is retarded when α-FAPbI3 is deposited upon mesoporous TiO2 scaffolds. It is hypothesized that this is due to the synergistic effect of the partial encapsulation of α-FAPbI3 by the mesoporous TiO2 and the elevated activation energy for the transition reaction associated with the substantial increase of the TiO2/α-FAPbI3 interfacial area in the mesoscopic system.

Chem Commun (Camb) ; 46(32): 5945-7, 2010 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-20596572


A facile single-step method was developed for synthesizing todorokite-type manganese oxide octahedral molecular seieves (OMS-1) and 2 x 4 tunnel structured manganese oxide (OMS-5) materials. Selection of starting materials and initial pH conditions in the syntheses are crucial.