High-Performance Ideal Bandgap Sn-Pb Mixed Perovskite Solar Cells Achieved by MXene Passivation.

Ideal bandgap (1.3-1.4 eV) Sn-Pb mixed perovskite solar cells (PSC) hold the maximum theoretical efficiency given by the Shockley-Queisser limit. However, achieving high efficiency and stable Sn-Pb mixed PSCs remains challenging. Here, piperazine-1,4-diium tetrafluoroborate (PDT) is introduced as spacer for bottom interface modification of ideal bandgap Sn-Pb mixed perovskite. This spacer enhances the quality of the upper perovskite layer and forms better energy band alignment, leading to enhanced charge extraction at the hole transport layer (HTL)/perovskite interface. Then, 2D Ti3C2Tx MXene is incorporated for surface treatment of perovskite, resulting in reduced surface trap density and enhanced interfacial electron transfer. The combinations of double-sided treatment afford the ideal bandgap PSC with a high efficiency of 20.45% along with improved environment stability. This work provides a feasible guideline to prepare high-performance and stable ideal-bandgap PSCs.

Large-Area Fabrication of Hexaazatrinaphthylene-Based 2D Metal-Organic Framework Films for Flexible Photodetectors and Optoelectronic Synapses.

2D conjugated metal-organic frameworks (c-MOFs) have emerged as promising materials for (opto)electronic applications due to their excellent charge transport properties originating from the unique layered-stacked structures with extended in-plane conjugation. The further advancement of MOF-based (opto)electronics necessitates the development of novel 2D c-MOF thin films with high quality. Cu-HHHATN (HHHATN: hexahydroxyl-hexaazatrinaphthylene) is a recently reported 2D c-MOF featuring high in-plane conjugation, strong interlayer π-π stacking, and multiple coordination sites, while the production of its thin-film form has not yet been reported. Herein, large-area Cu-HHHATN thin films with preferential orientation, high uniformity, and smooth surfaces are realized by using a convenient layer-by-layer growth method. Flexible photodetectors are fabricated, showing broadband photoresponse ranging from UV to short-wave infrared (370 to 1450 nm). The relatively long relaxation time of photocurrent, which arises from the trapping of photocarriers, renders the device's synaptic plasticity similar to that of biological synapses, promising its use in neuromorphic visual systems. This work demonstrates the great potential of Cu-HHHATN thin films in flexible optoelectronic devices for various applications.