Perovskite inorganic-organic solar cells are fabricated as a sandwich structure of mesostructured TiO2 as electron transport layer (ETL), CH3NH3PbI3 as active material layer (AML), and Spiro-OMeTAD as hole transport layer (HTL). The crystallinity, structural morphology, and thickness of TiO2 layer play a crucial role to improve the overall device performance. The randomly distributed one dimensional (1D) TiO2 nanowires (TNWs) provide excellent light trapping with open voids for active filling of visible light absorber compared to bulk TiO2. Solid-state photovoltaic devices based on randomly distributed TNWs and CH3NH3PbI3 are fabricated with high open circuit voltage Voc of 0.91 V, with conversion efficiency (CE) of 7.4%. Mott-Schottky analysis leads to very high built-in potential (Vbi) ranging from 0.89 to 0.96 V which indicate that there is no depletion layer voltage modulation in the perovskite solar cells fabricated with TNWs of different lengths. Moreover, finite-difference time-domain (FDTD) analysis revealed larger fraction of photo-generated charges due to light trapping and distribution due to field convergence via guided modes, and improved light trapping capability at the interface of TNWs/CH3NH3PbI3 compared to bulk TiO2.
Low-temperature processed highly efficient hole transport layer free carbon-based planar perovskite solar cells with SnO2 quantum dot electron transport layer
