Large ferro-pyro-phototronic effect in 0.5Ba(Zr_(0.2)Ti_(0.8))O_(3)-0.5(Ba_(0.7)Ca_(0.3))TiO_(3)thin films integrated on silicon for photodetection

Coupling together the ferroelectric,pyroelectric,and photovoltaic characteristics within a single material is a novel way to improve the performance of photodetectors.In this work,we take advantage of the triple multifunctionality shown by 0.5Ba(Zr_(0.2)Ti_(0.8))O_(3)-0.5(Ba_(0.7)Ca_(0.3))TiO_(3)(BCZT),as demonstrated in an Al/Si/SiOx/BCZT/ITO thin-film device.The Si/SiOx acts as an n-type layer to form a metal-ferroelectric-insulator-semiconductor heterostructure with the BCZT,and with Al and ITO as electrodes.The photo-response of the device,with excitation from a violet laser(405 nm wavelength),is carefully investigated,and it is shown that the photodetector performance is invariant with the chopper frequency owing to the pyro-phototronic effect,which corresponds to the coupling together of the pyroelectric and photovoltaic responses.However,the photodetector performance was significantly better than that of the devices operating based only on the pyro-phototronic effect by a factor of 4,due to the presence of ferroelectricity in the system.Thus,after a poling voltage of−15 V,for a laser power density of 230mW/cm^(2)and at a chopper frequency of 400Hz,optimized responsivity,detectivity,and sensitivity values of 13.1mA/W,1.7×10^(10)Jones,and 26.9,respectively,are achieved.Furthermore,ultrafast rise and fall times of 2.4 and 1.5μs,respectively,are obtained,which are 35,000 and 36,000 times faster rise and fall responses,respectively,than previous reports of devices with the ferro-pyro-phototronic effect.This is understood based on the much faster ferroelectric switching in ferroelectric thin films owing to the predominant 180°domains in a single direction out of plane.

X-ray-ultraviolet–visible-near-infrared photoresponsesrealized in a lead-free hybrid perovskite ferroelectricthrough light-induced ferro-pyro-phototronic effect

Due to the built-in electric field induced by spontaneous polarization in hybridperovskite (HP) ferroelectrics, the devices based on them exhibit excellent performancein self-powered photodetection. However, most of the self-poweredphotodetector are made of lead-based HP ferroelectrics and have a relativelynarrow photoresponse waveband. Although lead-free HPs solve the problem oflead toxicity, their optoelectronic performance is inferior to that of lead-basedHPs and photoresponse waveband is limited by its optical band gap, whichhinders their further application. To solve this problem, herein, a lead-free HPferroelectric (HDA)BiI5 (HDA is hexane-1,6-diammonium) with large spontaneouspolarization shows an enhanced photocurrent and achieves x-ray-ultraviolet–visible-near-infrared (x-ray-UV–Vis–NIR) photoresponse through theferro-pyro-phototronic (FPP) effect. The ferroelectric, pyroelectric, and photovoltaiccharacteristics coupled together in a single-phase (HDA)BiI5 ferroelectricis an effective way to improve the performance of the devices. What isparticularly attractive is that the FPP effect not only improves the optoelectronicperformance of (HDA)BiI_(5), but also achieves broadband photoresponsesbeyond its optical absorption range. Especially, the current boosting with anexceptional contrast of
1100% and 2400% under 520 and 637 nm, respectively,which is associated with FPP effect. Meanwhile, single crystal self-poweredphotodetector based on (HDA)BiI5 also exhibit significant FPP effects evenunder high-energy x-ray, which owns an outstanding sensitivity of 170.7 μCGy^(-1) cm^(-2) and a lower detection limit of 266 nGy s^(-1) at 0 V bias. Therefore, it is of great significance to study the coupling of multiple physical effects andimprove device performance based on lead-free HP ferroelectrics.