No abstract

In this work, planar inorganic perovskite solar cells (PSCs) with the simple structure of glass/ITO/SnO2/CsPbI2Br/C have been fabricated.

Carbon-based inorganic perovskite solar cells (C-PSCs) have attracted intensive attention owing to their low cost and superior thermal stability. However, the bulk defects in perovskites and interfacial energy level mismatch seriously undermine their performance. To overcome these issues, a multifunctional dualinterface engineering is proposed with a focus on low-temperature CsPbI 2 Br C-PSCs, where the potassium trifluoroacetate (KTFA) and the 4-trifluorophenyl methylammonium bromide (CF 3 PMABr) are introduced beneath and on top of the perovskite layer, respectively. It is found that TFAions locate at the SnO 2 /CsPbI 2 Br interface, whereas a small amount of K + ions diffuse into perovskite lattice to participate in nucleation and crystallization, resulting in more favored interfacial energy level alignment, improved film quality, passivated interfacial defects, released interfacial strain, as well as suppressed charge recombination and ion migration. Meanwhile, the CF 3 PMABr passivates I/Br vacancies and forms 2D perovskite capping layer to facilitate hole extraction at the CsPbI 2 Br/carbon interface. As a result, a remarkable power conversion efficiency (PCE) of 14.05% with an open-circuit voltage of 1.273 V is achieved. To the best of the authors' knowledge, it is currently the highest PCE reported for low-temperature CsPbI 2 Br C-PSCs. Furthermore, the nonencapsulated device exhibits improved moisture, thermal, and illumination stability in ambient air.

Hybrid photovoltaic devices based on poly(3-hexylthiophene) (P3HT) and an ordered electrospun ZnO nanofibrous network have been investigated. The diameters of the ZnO nanofibers have been controlled within 30-150 nm. The performance of the P3HT/ZnO hybrid solar cell is dependent on fabrication conditions, especially the thickness of the nanofibrous film. It has been found that the lifetime of carriers is lower in the device consisting of thicker ZnO nanofibrous films due to the higher density of surface traps in the ZnO nanofibers. The device with optimum fabrication conditions exhibits a power conversion efficiency of 0.51%.

In this work, the observations of different resistive switching polarities of epitaxial BaTiO3 (BTO) thin films fabricated by pulsed laser deposition are reported. The BTO films with various ferroelectric states and oxygen vacancy (VO) concentrations are achieved by carefully controlling the oxygen pressure during the depositions. For films with no ferroelectricity and high VO concentrations, the resistance will change from a low resistance state (LRS) to a high resistance state (HRS) during a positive voltage cycle (0 → 3 → 0 V), and from a HRS to a LRS during a negative voltage cycle (0 → −3 → 0 V). However, completely opposite RS polarity is observed for the films with weak ferroelectricity and intermediate VO concentrations. Such RS behaviors and polarity can be hardly observed or negligible for the films with good ferroelectricity and nearly free of VO. It is proposed that the unique resistance switching polarities of BTO films are attributed to the competition between the ferroelectricity and oxygen vacancy migration dynamics. Results clarify the complex RS mechanisms in the BTO films, and address the competing ferroelectricity and VO migration in modulating the RS behaviors of ferroelectric oxide‐based resistive memory devices.

A high-quality polycrystalline SnO 2 electron-transfer layer is synthesized through an in situ, low-temperature, and unique butanol-water solventassisted process. By choosing a mixture of butanol and water as a solvent, the crystallinity is enhanced and the crystallization temperature is lowered to 130 °C, making the process fully compatible with flexible plastic substrates. The best solar cells fabricated using these layers achieve an efficiency of 20.52% (average 19.02%) which is among the best in the class of planar n-ip-type perovskite (MAPbI 3 ) solar cells. The strongly reduced crystallization temperature of the materials allows their use on a flexible substrate, with a resulting device efficiency of 18%.

Triple cation perovskites (Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 ) have received lots of attention owing to the excellent stability and photovoltaic performance. However, the development toward efficient solar cells has been significantly impeded by its intrinsic precursor instability, as well as defective crystal surface. Herein, a strategy for introducing the additive of 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6) in the precursor solution, rendering an excellent stability of more than one month, and the defect passivation effect on the crystal surface are demonstrated. In those perovskite solar cells, a power conversion efficiency of 20.73% has been achieved with a substantially improved open-circuit voltage and fill factor. As evidenced by the density functional theory calculations, the fundamental reason relating to the enhanced performance is found to be the interaction effect between the 18C6 and cations, and in particular the formation of the 18C6/Pb complex. This finding represents an alternative strategy for achieving a stable precursor solution and efficient perovskite solar cells.

In the past decades, the inverted structure (p‐i‐n structure) perovskite solar cells (PVSCs) have been attracted more by the researchers owing to their ease of fabrication, cost‐effectiveness, lower processing temperature for the fabrication of large scale and flexible devices with negligible J−V hysteresis effects. The hole transporting layer (HTL) as a major served content of PVSCs has significant influence on light harvesting, carrier extraction and transportation, perovskite crystallization, stability and cost. Generally, the organic materials are used as HTLs which have less stability due to their morphology under thermal conditions; thus, leads to change in properties of them. A tantalizing possibility is replacement of p‐type inorganic materials instead of organic materials but the plenty of options are available for inorganic HTLs. However, the development of more variants for inorganic HTL is a major challenge. Till date, many materials have been reported, but their performances have not superseded that of their organic counterparts. Herein, the review on various inorganic HTLs based inverted PVSCs has been reported and analyzed their performances with appropriate properties such as proper energy level and high carrier mobility which are not only assisted with charge transport, but also improved the stability of PVSCs under ambient conditions.