Two-dimensional transition metal carbides and nitrides (MXenes) show tremendous potential for optoelectronic devices due to their excellent electronic properties. Here, a high-performance ultraviolet photodetector based on TiO 2 nanorod arrays/Ti 3 C 2 T x MXene van der Waals (vdW) Schottky junction by allsolution process technique is reported. The Ti 3 C 2 T x MXene modulated by the Au electrode increases its work function from 4.41 to 5.14 eV to form a hole transport layer. Complemented by the dangling bond-free surface of Ti 3 C 2 T x , the Fermi-level pinning effect is suppressed and the electric-field strength of the Schottky junction is enhanced, which promotes charge separation and transport. After applying a bias of −1.5 V, the photovoltaic effect is favorably reinforced, while the hole-trapping mechanism (between TiO 2 and oxygen) and reverse pyroelectric effect are largely eliminated. As a result, the responsivity and specific detectivity of the device with FTO/TiO 2 nanorod arrays/ Ti 3 C 2 T x /Au structure reach 1.95 × 10 5 mA W −1 and 4.3 × 10 13 cm Hz 1/2 W −1 (370 nm, 65 mW cm −2 ), respectively. This work provides an effective approach to enhance the performance of photodetectors by forming the vdW Schottky junction and choosing metal electrodes to modulate MXene as a suitable charge transport layer.
Nanomaterials such as quantum dots and 2D materials have been widely used to improve the performance of perovskite solar cells due to their favorable optical properties, conductivity, and stability. Nevertheless, the interfacial crystal structures between perovskites and nanomaterials have always been ignored while large mismatches can result in a significant number of defects within solar cells. In this work, cubic PbS nanosheets with (200) preferred crystal planes are synthesized through anisotropy growth. Based on the similar crystal structure between cubic PbS (200) and cubic‐phase formamidinium lead triiodide (α‐FAPbI3) (200), a nanoepitaxial PbS nanosheets‐FAPbI3 heterostructure with low defect density is observed. Attribute to the epitaxial growth, PbS nanosheets‐FAPbI3 hybrid polycrystalline films show decreased defects and better crystallization. Optimized perovskite solar cells perform both improved efficiency and stability, retaining 90% of initial photovoltaic conversion efficiency after being stored at 20 °C and 20% RH for 2500 h. Notably, the significantly improved stability is ascribed to the interfacial compression strain and chemical bonding between (200) planes of PbS nanosheets and α‐FAPbI3 (200). This study provides insight into high‐performance perovskite solar cells achieved by manipulating nanomaterial surfaces.
Chemical bath deposition (CBD) has been demonstrated as a remarkable technology to fabricate high‐quality SnO2 electron transport layer (ETL) for large‐area perovskite solar cells (PSCs). However, surface defects always exist on the SnO2 film coated by the CBD process, impairing the devices’ performance. Here, a facile periodic acid post‐treatment (PAPT) method is developed to modify the SnO2 layer. Periodic acid can react with hydroxyl groups on the surface of SnO2 films and oxidize Tin(II) oxide to Tin(IV) oxide. With the help of periodic acid, a better energy level alignment between the SnO2 and perovskite layers is achieved. In addition, the PAPT method inhibits interfacial nonradiative recombination and facilitates charge transportation. Such a multifunctional strategy enables to fabricate PSC with a champion power conversion efficiency (PCE) of 22.25%, which remains 93.32% of its initial efficiency after 3000 h without any encapsulation. Furthermore, 3 × 3 cm2 perovskite mini‐modules are presented, achieving a champion efficiency of 18.10%. All these results suggest that the PAPT method is promising for promoting the commercial application of large‐area PSCs.
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