PHOTOINDUCED TUNNELING SPECTROSCOPY OF RES2 - DRAMATIC INCREASE OF THE QUANTUM EFFICIENCY BY CHEMICAL TREATMENT

In this work we present a systematic study of the local photovoltaic p roperties of ReS2, using a scanning tunneling microscope (STM). The tu nneling junction of the STM was optically illuminated during the tunne ling process. The phase sensitive detected photo-induced tunneling cur rent (PITC) was studied as a function of wavelength and surface topogr aphy. In order to improve the performance of ReS2 solar cells, the sam ples were treated with NaI/I2 and EDTA solutions. Relative to the untr eated sample, the EDTA-treated samples show an increase in the photo-i nduced tunneling current by a factor of 8-10 in the whole spectral ran ge, the NaI/I-treated samples by 2-3. Two dimensional mapping of the P ITC was performed on an atomic scale and compared to the surface topog raphy.