Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 12, Issue 40, Pages 45533-45540Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.0c11805
Keywords
perovskite; scanning photocurrent microscopy; metal-semiconductor interface; Schottky junction; solid-state detector
Funding
- Los Alamos National Laboratory, Laboratory Directed Research and Development (LDRD) program [20180026DR]
- Los Alamos National Laboratory (LANL), Laboratory Directed Research and Development (LDRD) program
- National Nuclear Security Administration of the U.S. Department of Energy [89233218NCA000001]
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Halide perovskites are promising optoelectronic semiconductors. For applications in solid-state detectors that operate in low photon flux counting mode, blocking interfaces are essential to minimize the dark current noise. Here, we investigate the interface between methylammonium lead tri-iodide (MAPbI(3)) single crystals and commonly used high and low work function metals to achieve photon counting capabilities in a solid-state detector. Using scanning photocurrent microscopy, we observe a large Schottky barrier at the MAPbI(3)/Pb interface, which efficiently blocks dark current. Moreover, the shape of the photocurrent profile indicates that the MAPbI(3) single-crystal surface has a deep fermi level close to that of Au. Rationalized by first-principle calculations, we attribute this observation to the defects due to excess iodine on the surface underpinning emergence of deep band-edge states. The photocurrent decay profile yields a charge carrier diffusion length of 10-25 mu m. Using this knowledge, we demonstrate a single-crystal MAPbI(3) detector that can count single gamma-ray photons by producing sharp electrical pulses with a fast rise time of <2 mu s. Our study indicates that the interface plays a crucial role in solid-state detectors operating in photon counting mode.
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