In situ growth of an opal-like TiO2 electron transport layer by atomic layer deposition for perovskite solar cells

An orderly-arranged photonic crystal structure can produce a trapping effect to improve light utilization. Herein, an atomic layer deposition system and different sizes of polystyrene colloidal spheres were employed to in situ prepare an opal-like titanium oxide (TiO2) mesoporous electron transport layer for perovskite solar cells. Initially, a TiO2 layer was deposited on the spheres through an atomic layer deposition (ALD) system, and then the substrates were annealed to obtain hollow opal-like TiO2 structures. The as-prepared perovskite solar cells with the controlled opal-like TiO2 electron transport layer show an average power conversion efficiency (PCE) of 17.5 +/- 0.55, and the same ALD-prepared planar solar cells show an average PCE of 14.9 +/- 0.53. This work reveals that the opal-like nanostructure offers an efficient approach to high-performance perovskite solar cells.