Overcoming the voltage induced instability problem in perovskite semiconductor detectors

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Schematic illustration of the X-ray detector, where a perovskite semiconductor is sandwiched by two charge collection metal electrodes. Once X-ray hits the device, it generates electrical charges that can be collected by the metal electrodes for signal generation. The Los Alamos team developed a hydrophobic interface layer that can expel the water molecules. 

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With high dark resistivity and superior photoconductivity, two-dimensional lead-halide perovskites are a promising low-cost semiconductor for radiation photon sensing. Perovskite-based solid-state radiation detectors — semiconductor devices that directly convert a radiation photon to an electrical signal — deliver impressive X-ray sensitivities, surpassing the digital panels sold on the market. Despite the promising performance, their further development has been hampered by an electrical field induced instability.

In research featured on the cover of ACS Energy Letters, a team co-led by Center for Integrated Nanotechnologies scientists Wanyi Nie and Sergei Tretiak identified the cause of the voltage instability and developed a practical strategy to circumvent the problem. Their work provides a mechanistic understanding of the instability and a viable solution toward robust detector development.

To operate the detector at its maximum sensing efficiency, a high electrical field is typically applied to drive the X-ray ionized carriers across the semiconductor. However, perovskite materials are unstable under an electrical field, and a high sensitivity can only last for tens of minutes without protection. The team identified that the voltage-induced instability is directly tied to humidity levels of the two-dimensional perovskite detector’s operational environment. By testing the dark and photocurrent of its photodiode under inert and humid environments, they discovered that a high humidity level promotes a lag in the detector’s photocurrent response when a field is applied and accelerates the device’s failure under a constant electrical field stress.

Building on this observation, the team circumvented the moisture-accelerated device breakdown by growing a hydrophobic molecule over the perovskite surface. In so doing, they found that the device’s operational stability under voltage stress can be enhanced even when operating in a humid environment. The breakdown threshold voltage is pushed to a much higher level, allowing the detector to reach its maximum efficiently without a device failure. Quantum chemical simulations indicate that the hydrophobic molecule forms an atomically compact layer over the perovskite, serving as an efficient moisture barrier.

This work leveraged perovskite crystalline material growth, electronic device fabrication, and optical spectroscopy tools available at the Center for Integrated Nanotechnologies, the Laboratory’s high-performance computing capabilities, and the materials characterization capabilities at the Advanced Photon Source.

Funding and mission

The Los Alamos portion of the work was funded by a Laboratory Directed Research and Development Mission Foundations project and a J. Robert Oppenheimer Distinguished Postdoctoral Fellowship. The research was performed, in part, at the Center for Integrated Nanotechnologies, a DOE Office of Science Basic Energy Sciences user facility operated jointly by Sandia and Los Alamos national laboratories. This work supports the Laboratory’s Energy Security mission and the Materials for the Future capability pillar.

Reference

“Addressing the voltage induced instability problem of perovskite semiconductor detectors,” ACS Energy Letters, 7, 11, 3871 (2022); DOI: 10.1021/acsenergylett.2c02054. Authors: Hsinhan Tsai, Dibyajyoti Ghosh, Cheng-Hung Hou, Sergei Tretiak and Wanyi Nie (Los Alamos National Laboratory); Wyatt Panaccione and Lei Raymond Cao (The Ohio State University); Li-Yun Su and Leeyih Wang (National Taiwan University).

Technical contact: Wanyi Nie (MPA-CINT)