CH3NH3PbI3 perovskite solar cells are one of the most exciting technologies in the renewable energy field, resulting in over 20% power conversion efficiency. Deep understanding of the working principle is now required to turn the high efficiency solar cells into a reliable technology. In this work we have explored the role of deposition method on the crystallinity of perovskite films and its influence on the hysteresis behavior of the current-voltage characteristics. In addition Nb2O5 was used as hole blocking layer and its influence is also discussed. We have found that hysteresis is strongly dependent on both; perovskite deposition method and Nb2O5 thickness. The ideal condition where the hysteresis is suppressed or minimized was achieved by using the sequential deposition method for the perovskite semiconductor and a hole blocking layer of 50 nm.
Today numerous cyanine dyes that are soluble in organic solvents are available, driven by more than a century of
research and development of the photographic industry. Several properties specific to cyanine dyes suggest that
this material class can be of interest for organic solar cell applications. The main absorption wavelength can be
tuned from the ultra-violet to the near-infrared. The unparalleled high absorption coefficients allow using very
thin films for harvesting the solar photons. Furthermore, cyanines are cationic polymethine dyes, offering the
possibility to modify the materials by defining the counteranion. We here show specifically how counterions can
be utilized to tune the bulk morphology when blended with fullerenes. We compare the performance of bilayer
heterojunction and bulk heterojunction solar cells for two different dyes absorbing in the visible and the near-infrared.
Light-induced Electron Spin Resonance (LESR) was used to study the charge transfers of light induced
excitons between cyanine dyes and the archetype fullerene C60. LESR results show good correlation with the cell
performance.
Electrically Detected Magnetic Resonance (EDMR) was used to investigate the influence of dye doping molecules on
spin-dependent exciton formation in Aluminum (III) 8-hydroxyquinoline (Alq3) based OLEDs with different device
structures and temperature ranges. 4-(dicyanomethylene)-2-methyl-6-{2-[(4-diphenylamino-phenyl]ethyl}-4H-pyran
(DCM-TPA) and 5,6,11,12-tetraphenylnaphthacene (Rubrene) were used as dopants. A strong temperature dependence
have been observed for doped OLEDs, with a decrease of two orders of magnitude in EDMR signal for temperatures
above ~200 K. The signal temperature dependence were fitted supposing different spin-lattice relaxation processes. The
results suggest that thermally activated vibrations of dopants molecules induce spin pair dissociation, reducing the
signal.
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