Perovskite photovoltaics featuring solution-processable TiO2 as an interfacial electron-transporting layer display to improve performance and stability

Abstract

In this study we used solution-processable crystalline TiO₂ nanoparticles as an interfacial modified layer between the active layer and aluminum cathode to fabricate CH₃NH₃PbI₃/PCBM-based planar heterojunction perovskite photovoltaic (PPV) devices. We optimized the performance of the PPV device prepared without TiO₂ by varying the preheating temperature of the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT) substrate, obtaining a power conversion efficiency (PCE) of 6.3% under simulated AM 1.5 G irradiation (100 mW cm⁻²). After incorporating the TiO₂ layer, we obtained a much higher PCE of 7.0%. The TiO₂-containing PPV device exhibited extremely high stability (retaining ∼96% of its PCE after 1000 h) under long-term storage in a dark N₂-filled glove box; the unencapsulated device retained approximately 80% of its original efficiency (T₈₀) after 1 week under ambient conditions (ISOS-D-1; defined as 23 °C/50% RH). In contrast, the normal device was sensitive to ambient conditions with a value of T₈₀ at only 3 h. We attributed the improved device performance (PCE, stability) to the enhanced electron transporting, hole blocking, and barrier properties arising from the presence of the TiO₂ layer.