Millimeter-Scale Nonlocal Photo-Sensing Based on Single-Crystal Perovskite Photodetector

摘要

class="head no_bottom_margin" id="sec1title">IntroductionOrganometal trihalide perovskites (OTPs), a new family of optoelectronic materials, have recently attracted intense interest for photonic applications in photodetectors (, , , , , , ). Traditional OTP-based photodetectors based on solution-process polycrystalline OTP thin films show limited diffusion length (∼1 μm), resulting in many drawbacks in the photodetection performance (, , ). Thus, there is an urgent need to search for alternative materials with low trap states, long charge carrier lifetime, and long carrier diffusion length for the improvement of photodetectors (, , , ). Bulk perovskite single crystals with fewer grain boundaries are promising candidates with remarkable optoelectronic performances compared with traditional OTP thin films (, href="#bib17" rid="bib17" class=" bibr popnode">Ma et al., 2016, href="#bib21" rid="bib21" class=" bibr popnode">Saidaminov et al., 2015a, href="#bib24" rid="bib24" class=" bibr popnode">Shao et al., 2014, href="#bib25" rid="bib25" class=" bibr popnode">Shi et al., 2015, href="#bib31" rid="bib31" class=" bibr popnode">Yang et al., 2015, href="#bib32" rid="bib32" class=" bibr popnode">Zhang et al., 2016). Their excellent optoelectronic properties such as large absorption coefficient over a broad spectral range (href="#bib9" rid="bib9" class=" bibr popnode">Green et al., 2014), high charge carrier mobility (60 cm⁻² V⁻¹ s⁻¹) (href="#bib22" rid="bib22" class=" bibr popnode">Saidaminov et al., 2015b, href="#bib25" rid="bib25" class=" bibr popnode">Shi et al., 2015), proper bandgap energy (2.2 eV) (href="#bib19" rid="bib19" class=" bibr popnode">Miyata et al., 2015), and long exciton diffusion length (7.5 μm) (href="#bib28" rid="bib28" class=" bibr popnode">Wei et al., 2016, href="#bib31" rid="bib31" class=" bibr popnode">Yang et al., 2015) have been exploited to realize high-sensitivity photo-sensing devices of different detection bands from X-ray to visible light (href="#bib6" rid="bib6" class=" bibr popnode">Fang et al., 2015, href="#bib18" rid="bib18" class=" bibr popnode">Mao et al., 2003, href="#bib22" rid="bib22" class=" bibr popnode">Saidaminov et al., 2015b). Besides, synthetic routes of bulk perovskite single crystals are very simple and rely on self-assembly, which offers the advantages of cost-effectiveness and large-scale manufacture (href="#bib3" rid="bib3" class=" bibr popnode">Dong et al., 2015a, href="#bib16" rid="bib16" class=" bibr popnode">Liu et al., 2015b, href="#bib31" rid="bib31" class=" bibr popnode">Yang et al., 2015). However, previously demonstrated OTP-based photodetectors only show a local photoresponse and the effective photo-sensing area in these devices is mainly the photodetector channel (href="#bib14" rid="bib14" class=" bibr popnode">Li et al., 2015, href="#bib22" rid="bib22" class=" bibr popnode">Saidaminov et al., 2015b) or the hybrid channel where OTPs are in contact with other photoactive nanomaterials (such as semiconductor [href="#bib5" rid="bib5" class=" bibr popnode">Dou et al., 2014, href="#bib28" rid="bib28" class=" bibr popnode">Wei et al., 2016], quantum dots [href="#bib15" rid="bib15" class=" bibr popnode">Liu et al., 2015a, href="#bib20" rid="bib20" class=" bibr popnode">Qian et al., 2017], or two-dimensional materials [href="#bib12" rid="bib12" class=" bibr popnode">Kang et al., 2016, href="#bib13" rid="bib13" class=" bibr popnode">Lee et al., 2015, href="#bib17" rid="bib17" class=" bibr popnode">Ma et al., 2016, href="#bib27" rid="bib27" class=" bibr popnode">Wang et al., 2015]). The position-dependent photodetectors based on perovskite single crystals have not been demonstrated yet, which leads to the insufficient development of its advantages in long diffusion length.In many photo-sensing applications, illumination is not always precisely shining onto specific device locations, resulting in no photoresponse or a small response derived from a fraction of the illuminating power (href="#bib8" rid="bib8" class=" bibr popnode">Ghosh et al., 2010, href="#bib23" rid="bib23" class=" bibr popnode">Sarker et al., 2017). To overcome those limitations, it is of great importance to develop position-dependent photodetectors that can be operated without precise illumination on the device channel and to examine their position-dependent photoresponse characteristics. Up to now, very limited previous work has demonstrated position-dependent photodetectors by the combination of graphene and SiC substrate or using reduced graphene oxide (href="#bib23" rid="bib23" class=" bibr popnode">Sarker et al., 2017, href="#bib8" rid="bib8" class=" bibr popnode">Ghosh et al., 2010). However, the coupling of two materials (graphene and SiC) hinders photoelectric conversion efficiency and position dependence range (500 μm) of the device. Besides, bulk perovskite single crystals show larger single-crystal area compared with graphene, and the long carrier diffusion length allows the photo-generated charge carriers to be transported farther in perovskite single crystals, which provides potential for position-sensitive photodetection applications (href="#bib25" rid="bib25" class=" bibr popnode">Shi et al., 2015).In this article, we use a single material, CH3NH3PbBr3 (MAPbBr3) single crystals, to realize the position-sensitive photodetectors. Hard mask and electron beam evaporation were utilized to define specifically shaped source and drain on the perovskite single crystals. By setting up a custom-designed optoelectronic test platform, the position-sensitive photoresponse characteristics of the photodetector was measured by a focused laser beam, showing both position sensitivity and large-area photodetection. This position-sensitive device presents local optoelectronic performance of an optimal responsivity of 51 mA/W, which is a reasonable value when compared with previous reports (href="#bib22" rid="bib22" class=" bibr popnode">Saidaminov et al., 2015b). A remarkable ratio of photocurrent and dark current of 9 indicates potential applications in the construction of integrated optoelectronic systems. Meanwhile, photoresponse can be achieved for laser illumination not only on the perovskite channel but also on the area millimeter range away from the device channel. Two more samples were fabricated to prove the repeatability of the experiment, and more details are shown in href="#mmc1" rid="mmc1" class=" supplementary-material">Figure S1. To the best of our knowledge, this is a record for millimeter-range distance detection. Finally, the position-sensitive photoresponse was qualitatively explained by finite element analysis based on the dependence of carrier diffusion and recombination under the change of electric field on the position of illumination near the device channel.