Subscriber access provided by University of Newcastle, Australia
Article 3
3
3
3
3
3
Photodiode Response in a CHNHPbI/CHNHSnI Heterojunction Massimo Spina, Laszlo Mihaly, Karoly Holczer, Bálint Náfrádi, Andrea Pisoni, László Forró, and Endre Horváth ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b12392 • Publication Date (Web): 18 Jan 2017 Downloaded from http://pubs.acs.org on January 22, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Materials & Interfaces
Photodiode Response in a CH3NH3PbI3/CH3NH3SnI3 Heterojunction Massimo Spina1, László Mihály2, Károly Holczer3, Bálint Náfrádi1*, Andrea Pisoni1, László Forró1, Endre Horváth1 1
Laboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne
2
Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11790, USA 3
Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547, USA
Email:
[email protected] Keywords: photodiode; heterojunction; photovoltaics; photodetector; perovskite; methyl ammonium metal halide compounds;
Abstract. Here we report another surprising feature of the methyl ammonium metal halide material family, the photo-tunability of the diode response of a heterojunction made of CH3NH3PbI3 and its close relative, CH3NH3SnI3. In the dark state the device behaves as a diode, with the Sn homologue acting as the “p” side. The junction is extremely sensitive to illumination. A complete reversal of the diode polarity, the first observation of its kind, is seen when the junction is exposed to red laser light of 25 mW/cm2 or larger power density. This finding opens up the possibility for a novel class of opto-electronic devices. Introduction Since the discovery of its photovoltaic properties2 organometallic salt CH3NH3PbI3 became the subject of vivid interest. The material exhibits high light conversion efficiency3-4, it lases in red color5, and it can serve as the basis for light emitting diodes6 and photodetectors7-10. Also it shows unique properties for medical, thermoelectric and data storage applications.11-13 CH3NH3PbI3 belongs to the family of methyl ammonium metal halide compounds, with the general composition of MA-MX3, where MA stands for methyl ammonium, M is a metal ion (e.g.
ACS Paragon Plus Environment
ACS Applied Materials & Interfaces
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Page 2 of 11
Pb2+, Sn2+) and X represents Cl-, Br-, I- or F-.14-15 The [MX6]4- octahedra are the building blocks of a perovskite structure. For the current study, large single crystals (MAPbI3: 5-8 mm; MASnI3: 1-2 mm in size), expressing cube-like or needle-shape crystal habit have been prepared by precipitation from a concentrated aqueous solution as described in Ref13 and Supporting Information, Section 1. Detailed characterization of materials are reported elsewhere.9,
13
To
o
avoid sample degradation by moisture, the relative humidity at 23 C temperature was fixed to 21 %. The resistivity and the I-V characteristics of the materials have been studied separately in the dark state and also under illumination by white light and as a function of the temperature16. Representative I-V curves illustrating the photo-response are shown in the Supporting Information, Section 2. External quantum efficiency of the MAPbI3–MASnI3 junctions is characterized in the Supporting Information, Section 4. Junctions were prepared by touching a ~1 mm-size single crystal of MAPbI3 to the surface of a freshly prepared MASnI3 platelet. Electrical contacts were made by glued gold wires or tungsten pins pressed to the top of the MAPbI3 crystal and to the MASnI3 crystal close to the junction. A representative device is shown in Figure 1a. Owing to the presence of Iodine vapor at the material’s surface, the electrical contacts were susceptible to degradation with time, but the wellformed MAPbI3–MASnI3 junctions were stable. The I-V curves were obtained with a scan rate of 50 mV/s and a dwell time of 0.1 s, scanning from positive to negative voltages (i.e. from 0 V to +1 V, then to -1 V, and back to 0 V). In order to minimize sources of external noise, the measurements were performed in a home-built Faraday cage. A microscope objective and a
Figure 1. (a) Photograph of a photodiode similar to the ones used in this study. The MAPbI3 bulk single crystal is mechanically compressed to a platelet of MASnI3. Here the sample is contacted by gold wires, but most of the measurements were done in a two-probe configuration with tungsten pins pressed to the crystals. (b) Current-voltage characteristic of the diode in the dark state. The inset shows the low-voltage behavior (dots) and a fit to a ACS Paragon Plus Environment simple thermionic model (line). In the forward-biased region the Sn homologue is the positive terminal.
Page 3 of 11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Applied Materials & Interfaces
micromechanical stage were used to locate the device. We tested hundreds of such junctions and a subset of the devices – which resistance was dominated by MAPbI3–MASnI3 interface exhibited the behavior described below. The diode-like rectifying behavior of the device is evident in the I-V characteristic (Figure 1b). In the forward bias regime (V
