We report a simple and low-cost approach to enhance the longstanding stability of the perovskite solar cell (PSC) through the application of low-temperature grown SnO 2 nanorod (NR) arrays. SnO 2 NR arrays were fabricated by an aqueous synthesis method in the presence of hydrochloric acid and using thin compact SnO 2 as seeds. The influence of HCl concentration on the photovoltaic (PV) performance of the SnO 2 NR array based PSC device was investigated. The formed crystalline SnO 2 nanorods with square transversal-sections were oriented on the FTO facets in a well-defined and perpendicular fashion at an optimal HCl concentration. The optimized width and length for SnO 2 nanorods were 30 nm and 150 nm, respectively. Consequently, efficient and stable SnO 2 nanorod based perovskite devices were obtained with an average power conversion efficiency (PCE) of 16.57%. The SnO 2 nanorod array based PSCs demonstrated considerably better ultraviolet (UV) and ambient air stability than the planar SnO 2 and notably mesoporous TiO 2 solar cells. This paper provides a prospective scheme to grow high-quality three-dimensional SnO 2 nanorod arrays for highly stable and efficient PSCs.
Planar perovskite solar cells (PSCs) based on CH 3 NH 3 PbI 3- x (SCN) x (SCN: thiocyanate) active layer and low-temperature processed TiO 2 films are fabricated by a sequential two-step method in ambient air. Here, alkali thiocyanates (NaSCN, KSCN) are added into Pb(SCN) 2 precursor to improve the microstructure of CH 3 NH 3 PbI 3- x (SCN) x perovskite layers and performance of the as-prepared PSCs. At the optimum concentrations of alkali thiocyanates as additives, the as-prepared NaSCN-modified and KSCN-modified PSCs demonstrate the efficiencies of 16.59% and 15.63% respectively, being much higher than 12.73% of the reference PSCs without additives. This improvement is primarily ascribed to the enhanced electron transport , reduced recombination rates and much improved microstructures with large grain size and low defect density at grain boundaries. Importantly, it is revealed that the modified PSCs at the optimized concentrations of alkali thiocyanates additives exhibit remarkably improved stability than the reference PSCs against humid circumstance, and a continuous exposure to humid air without encapsulation over 45 days only records about 5% degradation of the efficiency. These findings provide a facile approach to fabricate efficient and stable PSCs by low processing temperature in ambient air, both of which are highly preferred for future practical applications of PSCs.
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