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Abstract:

Cesium lead halide perovskite nanocrystals (PNCs) exhibit promising prospects for application in optoelectronic devices. However, electroactivated near-infrared (NIR) PNC light-emitting diodes (LEDs) with emission peaks over 800 nm have not been achieved. Herein, we demonstrate the electroactivated NIR PNC LEDs based on Yb³⁺-doped CsPb(Cl_1-xBr_x)₃ PNCs with extraordinary high NIR photoluminescence quantum yields over 170%. The fabricated NIR LEDs possess an irradiance of 584.7 μW cm^-2, an EQE of 1.2%, and a turn-on voltage of 3.1 V. The ultrafast quantum cutting process from the PNC host to Yb³⁺ has been revealed as the main mechanism of electroluminescence (EL)-activated Yb³⁺ for the first time via exploring how the trend between the EL intensity of PNC and Yb³⁺ varies with different voltages along with the tendency of temperature- and doping-concentration-dependent PL and EL spectra. This work will extend the application of PNCs to optical communication, night-vision devices, and biomedical imaging.

Abstract:

Vacuum deposition is a solvent-free method suitable for growing thin films of metal halide perovskite (MHP) semiconductors. However, most reports of high-efficiency solar cells based on such vacuum-deposited MHP films incorporate solution-processed hole transport layers (HTLs), thereby complicating prospects of industrial upscaling and potentially affecting the overall device stability. In this work, we investigate organometallic copper phthalocyanine (CuPc) and zinc phthalocyanine (ZnPc) as alternative, low-cost, and durable HTLs in all-vacuum-deposited solvent-free formamidinium-cesium lead triodide [CH(NH₂)₂]_0.83Cs_0.17PbI₃ (FACsPbI₃) perovskite solar cells. We elucidate that the CuPc HTL, when employed in an “inverted” p–i–n solar cell configuration, attains a solar-to-electrical power conversion efficiency of up to 13.9%. Importantly, unencapsulated devices as large as 1 cm² exhibited excellent long-term stability, demonstrating no observable degradation in efficiency after more than 5000 h in storage and 3700 h under 85 °C thermal stressing in N₂ atmosphere.