Perovskite solar cells (PSC) have developed rapidly since the past decade with the aim to produce highly efficient photovoltaic technology at a low cost. Recently, physical and chemical defects at the buried interface of PSC including vacancies, impurities, lattice strain, and voids are identified as the next formidable hurdle to the further advancement of the performance of devices. The presence of these defects has unfavorably impacted many optoelectronic properties in the PSC, such as band alignment, charge extraction/recombination dynamics, ion migration behavior, and hydrophobicity. Herein, a broad but critical discussion on various essential aspects related to defects at the buried interface is provided. In particular, the defects existing at the surface of the underlying charge transporting layer (CTL) and the bottom surface of the perovskite film are initially elaborated. In situ and ex situ characterization approaches adopted to unveil hidden defects are elucidated to determine their influence on the efficiency, operational stability, and photocurrent-voltage hysteresis of PSC. A myriad of innovative strategies including defect management in CTL, the introduction of passivation materials, strain engineering, and morphological control used to address defects are also systematically elucidated to catalyze the further development of more efficient, reliable, and commercially viable photovoltaic devices.
Growing energy demands make cost-effective, high-performance perovskite solar cells (PSCs) desirable. However, their commercial applications are limited due to defect formation and instability. Passivation technologies help enhance their favorable traits. Herein, we propose a pioneering technique utilizing non-thermal plasma (NTP) synthesis for passivating inherent defects and optimizing the energy levels of perovskites. AC-NTP utilizes ionic charges and uniform electric fields to effectively neutralize defect-induced charge traps, acting as a field-effect passivator. This approach not only mitigates energetic defects, but also facilitates the transformation of NH4PbI3 into a CH3NH3PbI3 perovskite through a self-degassing mechanism. The perovskites synthesized using this method demonstrate notable advancements in their properties, as evidenced by X-ray diffraction, UV-vis spectroscopy, and scanning electron microscopy. These improvements include enhanced crystalline quality, superior optical characteristics, and precise nanoparticle size control, with an average size of 54 nm. In situ Rietveld refinement analysis reveals minimal PbI2 formation, resulting in fewer lead iodide inversion defects. Accordingly, the PSC fabricated by AC-NTP shows a PCE of 15.25%, significantly higher than that fabricated by the DC one (13.29%), which demonstrates improved stability under ambient conditions for over 160 hours. Hysteresis assessment, SCLC analysis, and Shockley diode modeling show our PSCs' low defect densities and high interface quality. Moreover, DFT was applied to indirectly analyze the effects of NTP on the perovskites, focusing on quantum confinement effects and lattice arrangement's influence on the optoelectronic characteristics of MAPbI3 nanoparticles. The findings confirm that NTP synthesis leads to more optimal PSCs, showing notable improvement in photovoltaics.
Here we use triple-cation metal-organic halide perovskite single crystals for the transistor channel of a flash memory device. Moreover, we design and demonstrate a 10 nm thick single-layer nanofloating gate. It consists of a ternary blend of two organic semiconductors, a p-type polyfluorene and an n-type fullerene that form a donor:acceptor interpenetrating network that serves as the charge storage unit, and of an insulating polystyrene that acts as the tunneling dielectric. Under such a framework, we realize the first non-volatile flash memory transistor based on a perovskite channel. This simplified, solution-processed perovskite flash memory displays unique performance metrics such as a large memory window of 30 V, an on/off ratio of 9 × 107, short write/erase times of 50 ms, and a satisfactory retention time exceeding 106 s. The realization of the first flash memory transistor using a single-crystal perovskite channel could be a valuable direction for perovskite electronics research.