Experimental demonstration of narrow-band rugate minus filters using rapidly alternating deposition technology

The design,fabrication and performance of narrow-band rugate minus filters are investigated in this paper.A method of fabricating graded-index coatings by rapidly alternating deposition of low(Si O_(2))and high(Al_(2)O_(3))refractive index materials is presented to fabricate a rugate structure.The narrow-band rugate minus filter design and fabrication approaches are discussed in detail.The experimental results,including transmittance spectrum,surface damage test and damage morphology investigated with a scanning electron microscope,demonstrate the high performance of the as-fabricated spatial filter and confirm the feasibility of the fabrication method for narrow-band rugate minus filters.

Suppression of ion migration in perovskite materials by pulse-voltage method

Hybrid halide perovskites have great potential for applications in optoelectronic devices.However,the typical ion migration in perovskite could lead to the non-repeatability of electrical measurement,instability of material,and degradation of device performance.The basic current–voltage behavior of perovskite materials is intricate due to the mixed electronic–ionic characteristic,which is still poorly understood in these semiconductors.Developing novel measurement schematic is a promising solution to obtain the intrinsic electrical performance without the interference of ion migration.Herein,we explore the pulse-voltage(PV)method on methylammonium lead tribromide single crystals to protect the device from the ion migration.A guideline is summarized through the analysis of measurement history and condition parameters.The influence of the ion migration on current–voltage measurement,such as repeatability and hysteresis loop,is under controlled.An application of the PV method is demonstrated on the activation energy of conductivity.The abruption of activation energy still exists near the phase transition temperature despite the ion migration is excluded by the PV method,introducing new physical insight on the current–voltage behavior of perovskite materials.The guideline on PV method will be beneficial for measuring halide perovskite materials and developing optoelectronic applications with new technique schematic.