High photoconductivity from hybrid bilayer

6 Oct 2016. NUS physicists have developed a high performance photodetector built on ahybrid bilayer of tungsten diselenide (WSe₂) and perovskite.

WSe₂ is a new class of two-dimensional (2D) material with potential applications for novel optoelectronic devices. However, the intrinsic defects caused by the selenium vacancies lower the electrical conductivity and photoconductivity of the WSe₂ monolayer, restricting its use in various applications. Recently, many research activities have been carried out by various international research groups to “heal” these defects in the WSe₂ monolayers.

A team led by Prof Chorng Haur SOW, from the Department of Physics, NUS has developed a method to “heal” the defects present in the WSe₂ monolayers. They developed effective methods for enhancing the performance of a WSe₂ monolayer photodetector using laser tailoring and perovskite functionalisation.

The team deposited a thin layer of organolead halide perovskite (CH₃NH₃PbI₃) via thermal evaporation onto a specially prepared WSe₂ monolayer. The unique combination of the focused laser beam technique to heal the defects in WSe₂, together with the use of the large absorption coefficient material CH₃NH₃PbI₃, led to the development of a high performance hybrid bilayer photodetector with an enhanced output which is three orders of magnitude better than the pristine device.

This carefully engineered approach represents a significant step towards improving the performance of 2D optoelectronics, extending the applications of 2D semiconductors in optical communication, integrated micro/nano-circuits, quantum information technology etc.

Figure shows the schematic diagram of a hybrid bilayer photodetector (left) and atomic structure of the interface of WSe₂–CH₃NH₃PbI₃.

References

JP Lu, A Carvalho, HW Liu, SX Lim, ZL AH Castro Neto, CH Sow. “Hybrid Bilayer WSe₂-CH₃NH₃PbI₃ Organolead Halide Perovskite as High Performance Photodetector”, Angewandte Chemie, 128, 12124-12128 (2016). DOI: 10.1002/anie.201603557.

JP Lu, A. Carvalho, XK Chan, HW Liu, B Liu,  ES Tok, KP Loh, AHC Castro Neto, CH Sow. “Atomic Healing of Defects in Transition Metal Dichalcogenides”. Nano Lett. 15, 3524 (2015).