High‐Gain and Low‐Driving‐Voltage Photodetectors Based on Organolead Triiodide Perovskites

Abstract

In this paper, we describe the fabrication and characterization of solution-processed CH 3 NH 3 PbI 3 photodetectors that combine a high photoconductive gain with a broad spectral response, ranging from the UV to the NIR. Benefi tting from the trapped-hole-induced electron injection, the CH 3 NH 3 PbI 3 photodetector works as a photodiode in the dark and shows large photoconductive gain under illumination. The maximum device gain reached 489 ± 6 at a very low driving voltage of −1 V.The devices studied here have a layered inverted structure ( Figure 1 a) where indium tin oxide (ITO) is the cathode, CH 3 NH 3 PbI 3 is the active layer, 4,4′-bis[(p-trichlorosilylpropylphenyl)phenylamino]-biphenyl (TPD-Si 2 ) serves as the hole transporting/electron blocking layer, molybdenum trioxide (MoO 3 ) is used for anode work function modifi cation, and silver (Ag) as the anode. The CH 3 NH 3 PbI 3 layers were prepared by thermal-annealing induced interdiffusion of the two perovskite precursors (PbI 2 , CH 3 NH 3 I) by way of a method that has recently been developed in our group to fabricate very effi cient solar cells with high yield. [ 8 ] In short, lead iodide (PbI 2 ) fi lms were deposited fi rst on ITO/glass substrates by spin-coating. A second layer consisting of methylammonium iodide (CH 3 NH 3 I) (hereafter MAI) was then spin-coated on top of the dried PbI 2 fi lm, followed by thermal annealing at 105 °C for 60 min. Scanning electron microscopy (SEM) measurements ( Figure S1, Supporting Information) showed that the interdiffusion method allows the preparation of CH 3 NH 3 PbI 3 fi lms on ITO that are continuous and uniform, which is particularly important for obtaining leakage-free photodetectors. The absorption curve in Figure 1 b shows that the CH 3 NH 3 PbI 3 fi lms have a broad absorption spectrum that ranges from 300 nm (UV) to 800 nm (NIR).The photo-and dark-current densities-voltage ( J -V ) curves of CH 3 NH 3 PbI 3 photodetectors (Figure 1 c) show a transition from a diode-rectifying behavior in the dark, to photoconduction under illumination. Under illumination, both the forward and the reverse bias currents increased dramatically, with the reverse bias current increasing more sharply than the forward bias current. The rectifying effect completely disappeared, and an ohmic conduction behavior (symmetrical photocurrent with respect to the y -axis) was observed when exposing the device to white light irradiation (10 mW cm −2 ). For comparison, the J -V curve of a high performance solar cell (where exactly the same CH 3 NH 3 PbI 3 fabrication procedure was applied) with almost 100% external quantum effi ciency under the same light intensity is also shown in Figure 1 c. The reference photovoltaic (PV) device has a structure of ITO/PEDOT:PSS/ MAPbI 3 /[6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) (20 nm)/C 60 (20 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (8 nm)/aluminium (Al) (100 nm). [ 8 ] Although Weak light sensing in the ultraviolet (UV), visible, and nearinfrared (NIR) range has a wide ...

Solution-processed semiconductors for next-generation photodetectors

“…72 This yielded photoconductive gains up to 400 with a response speed on the order of µs and 85 dB of linearity (Fig. 2e).…”

“…2e). 72 Also similar to organic semiconductors, MHPs can be combined with inorganic nanoparticles. Liu et al have recently reported on the use of PbS QDs in order to expand the spectral bandwidth of MHPs to the NIR.…”

Photodetectors Based on Organic–Inorganic Hybrid Lead Halide Perovskites

“…The commonly employed electrodes include gold (Au), silver (Ag), copper (Cu), platinum (Pt), titanium (Ti), aluminum (Al), graphene, and indium tin oxide (ITO) 35, 78, 79, 80, 81, 82. Different metals with varying Fermi levels will form Ohmic or Schottky contacts with OIHPs due to energy alignment, resulting in symmetrical and linear or asymmetrical and nonlinear I – V characteristics 82.…”

Perovskite Photovoltaics: Rare Functions of Organo Lead Halide in Solar Cells and Optoelectronic Devices

“…Several studies have clarified the rare ability of CH 3 NH 3 PbI 3 as photodetector to achieve high gain of photoinduced current in which quantum yield of photon-toelectron (current) far exceeds 100%. 38,75,76 For a semiconductor device to work as the photodetector, device is reverse-biased by external voltage so that the photocurrent density is maximized while the dark current is minimized. Here, ratio of photo-and dark-currents corresponds to the S/N ratio in photon detection.…”