High-performance photodetectors based on novel perovskite materials

Abstract

Photodetectors are typically used to capture photon or radiation energy and convert it into electrical signals, enabling the determination of light intensity or creating detailed images. While visible light detectors are commonly used in our daily lives, such as in photography with digital cameras and smartphones, near-infrared (NIR) light detectors offer distinct advantages, particularly in industrial and medical applications. In the medical field, NIR light detectors are highly desirable for real-time diagnosis as they enable the visualization of biological tissues, providing valuable insights into blood flow, oxygenation levels, tissue viability, and brain activity. Additionally, X-ray imaging techniques, including Computed Tomography (CT), are extensively employed in hospitals to produce detailed images of internal structures by effectively penetrating body tissues. Hybrid organic-inorganic halide perovskites, such as MAPbI3, have garnered significant attention as revolutionary materials for photodetectors due to their exceptional optoelectronic properties and low-temperature solution processability. These attributes enable the use of cost-effective facilities along with substantial photoresponse. However, typical lead(Pb)-based perovskite devices generally have limited responsivity beyond 800 nm wavelength, rendering them unsuitable for NIR light detection. To address this limitation, I have designed and fabricated highly sensitive broadband photodetectors using mixed tin/lead(Sn/Pb)-based perovskites. These devices exhibit ultrahigh responsivity, gain, and specific detectivity across a broad spectrum ranging from ultraviolet (UV) to NIR wavelengths. To optimize the interface properties of the perovskite phototransistors, I further employed a special three-step cleaning-healing-cleaning (C-H-C) treatment. This treatment resulted in a high hole mobility and low defect density within the channel, enhancing the overall performance. Consequently, phototransistors exhibit high responsivities up to 5.8 × 105 A W-1 and gains up to 1 × 106 in NIR regions. Meanwhile, a response time as fast as 80 ms is observed from the devices with optimized device design. The success of this work demonstrates a convenient approach to achieving high-performance phototransistors by manipulating the compositional gradient in mixed-metal perovskite channels. In the second work, photodetectors based on nontoxic, lead-free perovskites have been investigated. As Sn-based perovskites have been viewed as one of the most promising materials for these devices due to their relatively low bandgap and superior photoelectronic properties, I have designed a stacked two/three-dimensional (2D/3D) heterostructure in Sn-based perovskite films through a convenient vacuum drying process. The interface properties of the perovskite phototransistor are also further optimized via a special three-step C-H-C treatment, which results in an ultrahigh responsivity of up to 2 × 106 A W−1 at the NIR light region. Remarkably, the device also exhibits synaptic-like behavior, as demonstrated by its response of photocurrent activation to light stimuli, which closely resembles the memory consolidation observed in biological neural networks. This finding highlights the potential of high-performance optoelectronic devices utilizing 2D/3D lead-free perovskite heterojunctions to drive the advancement of diverse and eco-friendly technologies in the future. Single-crystal perovskites recently have sparked considerable interest due to their low trap density and have been employed as high-quality active layers in various optoelectronic devices, including X-ray detectors. Notably, X-ray imaging techniques, such as Computed Tomography (CT), are extensively used in hospitals, generating detailed images of internal structures by effectively penetrating body tissues. So, my third study focused on developing the detectors utilizing single-crystal mixed Sn/Pb-based perovskites. By employing the inverse temperature crystallization (ITC) method, high-quality perovskite crystals could be obtained within a few days, enabling broadband detection across the UV-visible-NIR spectrum, short response times below 200/600 µs, and on/off ratio exceeding 1000. Importantly, the encapsulated detectors also demonstrated remarkable sensitivity to X-ray radiation and maintained superior imaging resolution over 1000 hours in ambient air conditions. This research represents a promising approach to attain high-performance photodetectors by utilizing high-quality perovskite single crystals, paving the way for exciting future applications in the field.