2 research outputs found
Optical Properties of Nanoporous Germanium Thin Films
In the present article we report
enhanced light absorption, tunable size-dependent blue shift, and
efficient electronâhole pairs generation in Ge nanoporous films
(np-Ge) grown on Si. The Ge films are grown by sputtering and molecular
beam epitaxy; subsequently, the nanoporous structure is obtained by
Ge+ self-implantation. We show, by surface photovoltage spectroscopy
measurements, blue shift of the optical energy gap and strong signal
enhancement effects in the np-Ge films. The blue shift is related
to quantum confinement effects at the wall separating the pore in
the structure, the signal enhancement to multiple light-scattering
events, which result in enhanced absorption. All these characteristics
are highly stable with time. These findings demonstrate that nanoporous
Ge films can be very promising for photovoltaic applications
Photoinduced Current Transient Spectroscopy on Metal Halide Perovskites: Electron Trapping and Ion Drift
Metal halide perovskites (MHPs) are disruptive materials
for a
vast class of optoelectronic devices. The presence of electronic trap
states has been a tough challenge in terms of characterization and
thus mitigation. Many attempts based on electronic spectroscopies
have been tested, but due to the mixed electronicâionic nature
of MHP conductivity, many experimental results retain a large ambiguity
in resolving electronic and ionic charge contributions. Here we adapt
a method, previously used in highly resistive inorganic semiconductors,
called photoinduced current transient spectroscopy (PICTS) on lead
bromide 2D-like ((PEA)2PbBr4) and standard â3Dâ
(MAPbBr3) MHP single crystals. We present two conceptually
different outcomes of the PICTS measurements, distinguishing the different
electronic and ionic contributions to the photocurrents based on the
different ion drift of the two materials. Our experiments unveil deep
level trap states on the 2D, âion-frozenâ (PEA)2PbBr4 and set new boundaries for the applicability
of PICTS on 3D MHPs