Resolving Mixed Intermediate Phases in Methylammonium-Free Sn-Pb Alloyed Perovskites for High-Performance Solar Cells

The complete elimination of methylammonium(MA)cations in Sn-Pb composites can extend their light and thermal stabilities.Unfortunately,MA-free Sn-Pb alloyed perovskite thin films suffer from wrinkled surfaces and poor crystallization,due to the coexistence of mixed intermediate phases.Here,we report an additive strategy for finely regulating the impurities in the intermediate phase of Cs_(0.25)FA_(0.75)Pb_(0.6)Sn_(0.4)I_(3)and,thereby,obtaining high-performance solar cells.We introduced d-homoserine lactone hydrochloride(D-HLH)to form hydrogen bonds and strong Pb-O/Sn-O bonds with perovskite precursors,thereby weakening the incomplete complexation effect between polar aprotic solvents(e.g.,DMSO)and organic(FAI)or inorganic(CsI,PbI_(2),and SnI_(2))components,and balancing their nucleation processes.This treatment completely transformed mixed intermediate phases into pure preformed perovskite nuclei prior to thermal anneal-ing.Besides,this D-HLH substantially inhibited the oxidation of Sn^(2+) species.This strategy generated a record efficiency of 21.61%,with a Voc of 0.88 V for an MA-free Sn-Pb device,and an efficiency of 23.82%for its tandem device.The unencapsulated devices displayed impressive thermal stability at 85℃ for 300 h and much improved continuous operation stability at MPP for 120 h.

Influence of imidazole derivatives on the dielectric and energy storage performance of epoxy

Imidazoles are widely used as curing agents and accelerators for fabricating crosslinked epoxy materials applied in electrical and electronic fields.However,the intrinsic chemical structure of imidazole derivatives would greatly influence the polymerisation process,and further change the electrical properties,which was not emphasised.To achieve an in-depth understanding,commonly used imidazole only containing pyridine-type nitrogen and imidazole with both pyridine and pyrrole-type nitrogen were selected in this study.Electrical properties including dielectric properties,volume resistivity,breakdown strength,and especially energy storage performances were systematically investigated.We figured out that higher breakdown strength,glass transition temperature,and lower dielectric loss can be achieved with imidazole containing pyrrole-type nitrogen.Structure-induced curing mechanism diversity and the generated differences in polymer network were highlighted.With the capability to incorporate into the polymer network,the dielectric constant/loss of epoxy cured by imidazole containing pyrrole-type nitrogen is less sensitive with variation in concentration and a high breakdown strength of 577.9 MV/m was achieved.On the contrary,conspicuous decrease in the breakdown strength and increase in dielectric loss of the epoxy cured by imidazole only containing pyridine-type nitrogen were observed,especially at high concentration.Moreover,we also found that the epoxy can be fabricated into films with an attractive energy storage density/efficiency of 1.1 J/cm^(3)/97%@200 MV/m,which is twice of the commercial dielectric polypropylene film under the same electric field.