Organic-inorganic hybrid perovskite films possess superior optoelectronic properties, including bandgap tunability, high absorption coefficient, well-balanced charge carrier mobility and long electron-hole diffusion length. Hence it can serve as sensitizers in solar cells, photodetectors, pumped lasers and light-emitting diodes. However, the crystallographic defect passivation and suppression of organic-inorganic hybrid perovskite at the grain boundaries are crucial for efficient and stable perovskite photodetectors (PPDs). Herein, a bulk heterojunction (BHJ) fabricated by the two-step spin-coating method facilitates high-quality perovskite film formation while reducing the non-radiative recombination within the photoactive layer, enhancing the photosensitivity performance of PPDs based on BHJ configuration. Specifically, sulfonated graphene (SGA) was used as a functional passivator to interact with Pb2+ at the surface and grain boundaries due to its large specific surface area and high binding energy with lead ion, thereby ameliorating the device stability and carrier transport capacity within perovskite films, resulting in a lower dark current density and a higher photocurrent density. Consequently, the PPD based on the BHJ configuration achieves a responsivity of 570 mA/W and the specific detectability of 6.3×1011 Jones under the bias voltage of −1 V with the 532 nm laser illumination intensity of 0.5 μW/cm2 and a linear dynamic range of 126 dB. The PPD based on BHJ configuration shows ultrahigh response rates of 0.3 μs and 52.7 μs for the rise and fall times at zero bias, respectively, which is attributed to efficient carrier extraction and the lower defect density. The grain boundary passivation strategy of SGA modification develops a practical approach to ameliorate PPD performance and stability.
Photodetectors are the fundamental element for realizing scientific and commercial applications. Perovskites have attracted much attention as alternative materials for next generation photodetectors, owing to the high absorption coefficient of visible light, high carrier mobility, and unusually high defect tolerance . Previous studies show the working waveband of perovskite photodetector usually be confined to the visible light range. However, the weak absorption in the infrared and the low carrier mobility of perovskites limit the fabrication of high-performance photodetectors. Introducing graphene and its derivatives into perovskites is a proven and effective method to improve the optoelectronic properties. In this work, sulfonated graphene oxide (s-GO) was blended into the organo-inorganic methylammonium lead halide perovskites to fabricate the high-performance near infrared (NIR) photodetector. s-GO is an efficient carrier transport, thereby carrier mobility of doped perovskites can be effectively increased. After blending, the photodetector is twice the responsivity at 1064nm laser of the photodetector with no additives. Meanwhile, the fast response (less than 17 ms) and the impressive low noise equivalent power are achieved.
Three-dimensional (3D) perovskite photodetectors (PPDs) demonstrate remarkable photoelectric detection ability, but the intrinsic instability of 3D perovskite films against moisture, oxygen, and temperature has been a roadblock for achieving great stability and reliability of the resulting PDs, which can be mainly ascribed to the inevitable defects on surfaces and grain boundaries that can incur nonradiative charge recombination to impair device performance and initiate the degradation of perovskites. In this work, we introduced the two-dimensional (2D) perovskite material PEAI to fabricate a high-performance and stable 2D/3D stacked PPD. As a result, the responsivity of the PEAI processed PPD (PEAI-PPD) reached 1.19 A/W under the illumination of 532 nm laser with the power density of 5 μW/cm2 at bias voltage of −1 V, and retains 80.15% of the initial value after 16 days of nonencapsulated storage at 10%-15% relative humidity (RH). Our work provides a simple and effective method for the fabrication of high-performance and stable 2D/3D stacked PPDs, which has great application potential in visible light communication, imaging and environmental monitoring under complex environmental conditions.
The preparation of high-quality perovskite films with optimal morphologies is important for achieving high-performance perovskite photodetectors (PPDs). An effective strategy to optimize the morphologies is to add antisolvents during the spin-coating steps. In this work, an environment-friendly antisolvent ethyl acetate (EA) was employed to improve the quality of perovskite films, which can effectively regulate the formation of an intermediate phase staged in between a liquid precursor phase and a solid perovskite phase due to its moderate polarity, and further promote the homogeneous nucleation and crystal growth in the subsequent annealing process, thus leading to the formation of high-quality perovskite films and enhanced photodetector (PD) performance. As a result, the responsivity of the PPDs reached 0.85 A W-1 under the illumination of 532 nm laser with the power density of 6.37 μW cm-2 at bias voltage of -2 V. The corresponding detectivity reached 3.27 × 1011 Jones, while the rise time and fall time are 256 ns and 370 ns, respectively. These results demonstrates that our developed solution-processed method with EA as antisolvent has remarkably advantages for the fabrication of high-performance PPDs and can provide a reference for the other similar research work.
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