Defect density is one of the most significant characteristics of perovskite single crystals(PSCs)that determines their optical and electrical properties,but few strategies are available to tune this property.Here,we demonstrate that voltage regulation is an efficient method to tune defect density,as well as the optical and electrical properties of PSCs.A three-step carrier transport model of MAPbBr_(3) PSCs is proposed to explore the defect regulation mechanism and carrier transport dynamics via an applied bias.Dynamic and steady-state photoluminescence measurements subsequently show that the surface defect density,average carrier lifetime,and photoluminescence intensity can be efficiently tuned by the applied bias.In particular,when the regulation voltage is 20 V(electrical poling intensity is 0.167 Vμm^(−1)),the surface defect density of MAPbBr_(3) PSCs is reduced by 24.27%,the carrier lifetime is prolonged by 32.04%,and the PL intensity is increased by 112.96%.Furthermore,a voltage-regulated MAPbBr_(3) PSC memristor device shows an adjustable multiresistance,weak ion migration effect and greatly enhanced device stability.Voltage regulation is a promising engineering technique for developing advanced perovskite optoelectronic devices.
A layered perovskite oxide Y0.8Ca0.2Ba Co Fe O5+δ(YCBCF) was synthesized as a novel cathode material for intermediate-temperature solid oxide fuel cells(IT-SOFCs) by citric acid-nitrates self-propagating combustion method. The phase and microstructure of YCBCF were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM), respectively. The average thermal expansion coefficient(TEC) of YCBCF was 14.6×10–6 K–1, which was close to other materials of SOFC at the range of RT–1000 oC. An open-circuit potential of 0.75 V and a maximum output power density of 426 m W/cm2 were obtained at 650 oC in a Sm0.2Ce0.8O1.9(SDC)-based anode-supported SOFC by using humidified(~3% H2O) hydrogen as fuel and static air as oxidant. The results indicated that the YCBCF was a promising cathode candidate for IT-SOFCs.
