Effect of layer-by-layer assembled SnO2 interfacial layers in photovoltaic properties of dye-sensitized solar cells.

Ultrathin SnO2 layers were deposited on FTO substrate by the layer-by-layer (LbL) self-assembly technique (NPs) and cationic poly(allylamine hydrochloride) (PAH). utilizing negatively charged 2.5 nm sized SnO2 nanoparticles For the construction of dye-sensitized solar cells (DSC), the bulk TiO2 layer was deposited over the (PAH/SnO2)(n) (n = 1-10) and subsequently calcined at 500 degrees C to remove organic components. With introducing four layers of self-assembled SnO2 interfacial layer (IL), the short circuit current density (J(sc)) of DSCs was increased from 8.96 to 10.97 mA/cm(2), whereas the open circuit voltage (V-oc) and fill factor (FF) were not appreciably changed. Consequently, photovoltaic conversion efficiency (eta) was enhanced from 5.43 to 6.57%. Transient photoelectron spectroscopic analyses revealed that the ultrathin SnO2 layer considerably increased the electron diffusion coefficient (D-e) in TiO2 layer, but the electron lifetime (tau(e)) was decreased unexpectedly. The observed unusual photovoltaic properties would be caused by the unique conduction band (CB) location of the SnO2, inducing the cascadal energy band matching among the CBs of TiO2, SnO2, and FTO.