SEMINAR LMGP - 18.05.2021 - Lorenzo BOTTIGLIERI

“ Development of transparent p- type semiconducting thin films and its integration in devices ”


Lorenzo BOTTIGLIERI
Ph.D. student,
Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP
 

The breakthrough of transparent electronic is hindered by the lack of p-type transparent conductive oxides with great optical and electrical performances. Among various candidate, CuCrO₂ represent one of the most promising material for the application in transparent optoelectronic devices. In this talk, I will illustrate the enhancement of functional properties achieved in out of stoichiometry CuCrO₂ thin films synthesized by Aerosol Assisted chemical vapor deposition. We obtained a decreasing in resistivity and in Eg in Cu-rich films with an optimal composition for Cu/(Cu+Cr) = 67%. We report here the deposition of two classes of materials: Cu-rich CuCrO₂ films, with low resistivity (<0.1 Ω.cm) and wide Eg of 3.15 eV, and films consisting in a nanocomposite of CuCrO₂ and Cu₂O, presenting a measurable Hall-effect p-type mobility of 0.65 cm²V^-1s^-1 and a Eg of 3.0 eV. We further demonstrated the optoelectronic properties of out of stoichiometry CuCrO₂ through the integration of this material in different transparent devices. Firstly, out of stoichiometry CuCrO₂ have been integrated as hole transport layer (HTL), representing a promising alternative to unstable PEDOT:PSS. The conception of hybrid photovoltaic, constituted by organic and inorganic materials, is revealed an auspicious approach to enhance the efficiencies and the stability of the solar cells. The effect of the composition of the HTL varied between 40 and 100%, on the Power Conversion Efficiency (PCE) and stability in atmospheric conditions was studied. The failure mechanism is also briefly discussed. The optimal cationic ratio was achieved for Cu/(Cu+Cr)= 65% with the highest PCE of this work equal to 3.1%, mainly due to an increase in short circuit current. This composition corresponds to the best trade-off between transparency, conductivity, level energy, bandgap, leading to a overall increase in short circuit current.The reusability of the functionalized substrates, glass/ITO/CuCrO₂, was tested by the elimination of top part Aluminum/ETL/Active layer. A soft chemical procedure is highlighted for the recycling of organic solar cells, without affecting the properties of the HTL.

Out of stoichiometry CuCrO₂ thin films were coupled with ZnO deposited by Spatial ALD in a planar p-n junction. This transparent diode was entirely synthesized by chemical deposition techniques at low temperature and atmospheric pressure, with no required post-deposition treatment. It shows an extremely high rectifying behavior. The combination of Cu₂O+CuCrO₂ and ZnO shows an extremely high rectifying behavior, Ion/Ioff (±3V) around 10000, and a transmittance in the visible around 70%. The fitting of the diode characteristic led to values of 2.5, 3 Ω.cm2 and 5*105 Ω.cm2 for the ideality factor, series resistance, and shunt resistance, respectively.