CsPbCl 3 metal halide perovskite photodetectors (PDs) are prepared via thermal evaporation and 75 °C in situ annealing on Si/SiO 2 substrates, and their photoresponse as well as the morphology, structure, and photophysical properties are investigated. Wide spectrum photoresponse ranging from 350 to 980 nm has been achieved with optimal responsivity (R) of 2364, 3766, and 268 A/W at wavelengths (λ) of 420, 680, and 980 nm, respectively. Such photoresponse behavior can be attributed to the parallel photoresponse from both CsPbCl 3 and Si based on the UPS (ultraviolet photoelectron spectrometry) and XPS (X-ray photoelectron spectroscopy) results. Yb 3+ doped CsPbCl 3 PDs with the photosensing layer structure of CsPbCl 3 (50 nm)/YbCl 3 (30 nm)/CsPbCl 3 (50 nm) have been prepared, and it was found that Yb 3+ dopant is capable of realizing obviously shorter exciton lifetime at 420 nm, lower trap density, as well as remarkably higher carrier mobility due to the combined effects of energy transfer from CsPbCl 3 to Yb 3+ and defect passivation from Yb 3+ , leading to remarkable improvement of the photoresponse performance with optimal R (2709, 6340 and 3573A/W), noise equivalent power (NEP) (5.64 × 10 −7 , 2.51 × 10 −7 , and 4.38 × 10 −7 W), and specific detectivity (D*) (1.84 × 10 11 , 3.24 × 10 11 , and 1.5 × 10 11 cm Hz 1/2 W −1 ) compared to those of pristine CsPbCl 3 at λ of 420, 720, and 980 nm, respectively. Especially at the NIR λ of 980 nm, 10-fold higher R is achieved after Yb 3+ incorporation. The upconversion processing of Yb 3+ can also be responsible for the enhanced wide spectrum photoresponse of Yb 3+ doped CsPbCl 3 . Our study provides a practical way to realize wide spectrum perovskite PDs by simply connecting the perovskite to Si substrates by the Au electrodes.
Two-dimensional transition metal chalcogenides (TMDCs) have attracted great interest due to their unique semiconductor properties. Among all TMDC materials, MoS2 and WS2 are promising for composing heterostructures. However, traditional TMDC heterostructure fabrication depends on transfer process, with drawbacks of interface impurity and small size. In this work, a two-step chemical vapor deposition (CVD) process was applied to synthesize large-scale WS2/MoS2 heterostructure. Surface morphology and crystal structure characterizations demonstrate the high-quality WS2/MoS2 heterostructure. The WS2/MoS2 heterostructure photodetector fabricated by photolithography exhibits an enhanced photoresponsivity up to 370 A W-1 in comparison with single WS2 or MoS2 devices. This study suggests a direct CVD growth of large-scale TMDC heterostructure films with clean interface. The built-in electric field at interface contributes to the separation of photo-generated electron-hole pairs, leading to enhanced photocurrent and responsivity, and showing promising potentials in photo-electric applications.
The CsSnBr3 photodetectors are fabricated by thermal evaporation and 75°C in-situ annealing, and the effect of in-situ annealing on the morphology, structure, exciton dynamics and photoresponse of thermally evaporated CsSnBr3 films are investigated. Especially, temperature-dependent steady-state photoluminescence (PL) and transient PL decaying have been analyzed in details for understanding the exciton dynamics. Meanwhile, effect of annealing on the activation energy for trap sites (Ea), exciton binding energy (Eb), activation energy for interfacial trapped carriers (ΔE), trap densities and carriers mobilities are studied and the annealed (A-CsSnBr3) reveals obviously lower Eb and trap density together with notably higher carrier mobility than those of the unannealed (UA-CsSnBr3). Temperature dependence of the integrated PL intensity can be ascribed to the combining effect of the exciton dissociation, exciton quenching through trap sites and thermal activation of trapped carriers. The temperature dependent transient PL decaying analysis indicates that the PL decaying mechanism at low and high temperature is totally different from that in intermediate temperature range, in which combing effect of free exciton and localized state exciton decaying prevail. The beneficial effects of the in-situ annealing on the photoresponse performance of the CsSnBr3 films can be demonstrated by the remarkable enhancement of the optimal responsivity (R) after in-situ annealing which increases from less than 1A/W to 1350A/W as well as dramatically improved noise equivalent power (NEP), specific detectivity D* and Gain (G).
The transition metal dichalcogenides (TMDC)/metal halide perovskite photodetectors provides a promising new route for the realization of high-performance photodetectors owing to their unique optoelectronic features. However, previous studies usually focus...
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