Bimolecularly passivated interface enables efficient and stable inverted perovskite solar cells.

Compared with the n-i-p structure, inverted (p-i-n) perovskite solar cells (PSCs) promise increased operating stability, but these photovoltaic cells often exhibit lower power conversion efficiencies (PCEs) because of nonradiative recombination losses, particularly at the perovskite/C60 interface. We passivated surface defects and enabled reflection of minority carriers from the interface into the bulk using two types of functional molecules. We used sulfur-modified methylthio molecules to passivate surface defects and suppress recombination through strong coordination and hydrogen bonding, along with diammonium molecules to repel minority carriers and reduce contact-induced interface recombination achieved through field-effect passivation. This approach led to a fivefold longer carrier lifetime and one-third the photoluminescence quantum yield loss and enabled a certified quasi-steady-state PCE of 25.1% for inverted PSCs with stable operation at 65°C for >2000 hours in ambient air. We also fabricated monolithic all-perovskite tandem solar cells with 28.1% PCE.

Solid-Ionic Memory in a van der Waals Heterostructure.

Defect states dominate the performance of low-dimensional nanoelectronics, which deteriorate the serviceability of devices in most cases. But in recent years, some intriguing functionalities are discovered by defect engineering. In this work, we demonstrate a bifunctional memory device of a MoS2/BiFeO3/SrTiO3 van der Waals heterostructure, which can be programmed and erased by solely one kind of external stimuli (light or electrical-gate pulse) via engineering of oxygen-vacancy-based solid-ionic gating. The device shows multibit electrical memory capability (>22 bits) with a large linearly tunable dynamic range of 7.1 × 106 (137 dB). Furthermore, the device can be programmed by green- and red-light illuminations and then erased by UV light pulses. Besides, the photoresponse under red-light illumination reaches a high photoresponsivity (6.7 × 104 A/W) and photodetectivity (2.12 × 1013 Jones). These results highlighted solid-ionic memory for building up multifunctional electronic and optoelectronic devices.