In recent years, substantial progress has been made in developing perovskite light-emitting diodes with near-infrared, red and green emissions and over 20% external quantum efficiency. However, the development of perovskite light-emitting diodes with blue emission remains a great challenge, which retards further development of full-color displays and white-light illumination based on perovskite emissive materials. Here, firstly, through composition and dimensional engineering, we prepare quasi-two-dimensional perovskite thin films with improved blue emission, taking advantages of reduced trap density and enhanced photoluminescence quantum yield. Secondly, we find a vertically non-uniform distribution of perovskite crystals in the PEDOT:PSS/perovskite hybrid film. Through modulating the position of the recombination zone, we activate the majority of quasi-two-dimensional perovskite crystals, and thus demonstrate the most efficient blue perovskite light-emitting diode to date with emission peak at 480 nm, record luminance of 3780 cd m −2 and record external quantum efficiency of 5.7%.
In this work, a SnO /ZnO bilayered electron transporting layer (ETL) aimed to achieve low energy loss and large open-circuit voltage (V ) for high-efficiency all-inorganic CsPbI Br perovskite solar cells (PVSCs) is introduced. The high-quality CsPbI Br film with regular crystal grains and full coverage can be realized on the SnO /ZnO surface. The higher-lying conduction band minimum of ZnO facilitates desirable cascade energy level alignment between the perovskite and SnO /ZnO bilayered ETL with superior electron extraction capability, resulting in a suppressed interfacial trap-assisted recombination with lower charge recombination rate and greater charge extraction efficiency. The as-optimized all-inorganic PVSC delivers a high V of 1.23 V and power conversion efficiency (PCE) of 14.6%, which is one of the best efficiencies reported for the Cs-based all-inorganic PVSCs to date. More importantly, decent thermal stability with only 20% PCE loss is demonstrated for the SnO /ZnO-based CsPbI Br PVSCs after being heated at 85 °C for 300 h. These findings provide important interface design insights that will be crucial to further improve the efficiency of all-inorganic PVSCs in the future.
SummaryLow-band-gap metal halide perovskite semiconductor based on mixed Sn/Pb is a key component to realize high-efficiency tandem perovskite solar cells. However, the mixed perovskites are unstable in air due to the oxidation of Sn2+. To overcome the stability problem, we introduced N-(3-aminopropyl)-2-pyrrolidinone into the CH3NH3Sn0.5Pb0.5IxCl3-x thin film. The carbonyl group on the molecule interacts with Sn2+/Pb2+ by Lewis acid coordination, forming vertically oriented 2D layered perovskite. The 2D phase is seamlessly connected to the bulk perovskite crystal, with a lattice coherently extending across the two phases. Based on this 2D/3D hybrid structure, we assembled low-band-gap Sn-based perovskite solar cells with power conversion efficiency greater than 12%. The best device was among the most stable Sn-based organic-inorganic hybrid perovskite solar cells to date, keeping 90% of its initial performance at ambient condition without encapsulation, and more than 70% under continuous illumination in an N2-filled glovebox for over 1 month.
In the past few years, substantial progress has been made in perovskite light-emitting devices. Both pure green and infrared thin-film perovskite light-emitting devices with external quantum efficiency over 20% have been successfully achieved. However, pure-red and blue thin-film perovskite light-emitting diodes still suffer from inferior efficiency. Therefore, the development of efficient and stable thin-film perovskite light-emitting diodes with pure-red and blue emissions is urgently needed for possible applications as a new display technology and solid-state lighting. Here, we demonstrate an efficient light-emitting diode with pure-red emission based on polymer-assisted in situ growth of highquality all-inorganic CsPbBr 0.6 I 2.4 perovskite nanocrystal films with homogenous distribution of nanocrystals with size 20−30 nm. With this method, we can dramatically reduce the formation temperature of CsPbBr 0.6 I 2.4 and stabilize its perovskite phase. Eventually, we successfully demonstrate a pure-red-emission perovskite light-emitting diode with a high external quantum efficiency of 6.55% and luminance of 338 cd/m 2 . Furthermore, the device obtains an ultralow turn-on voltage of 1.5 V and a half-lifetime of over 0.5 h at a high initial luminance of 300 cd/m 2 .
Recent studies of sky‐blue perovskite light‐emitting diodes (PeLEDs) have extensively promoted optimal device design to achieve an external quantum efficiency (EQE) above 12%. However, the development of thin‐film deep‐blue PeLEDs lags dramatically behind, especially with regards to meeting the latest Rec. 2020 standard. A trichloro(3,3,3‐trifluoropropyl) silane post‐treatment that drives the emission of perovskite into the deep‐blue region, ranging from 440 to 460 nm, which meets the Rec. 2020 standard, is proposed. The chlorine ions released from the organotrichlorosilane molecules during their polycondensation reaction provide an addition halide source to fine tune the composition of the mixed halide perovskite films, leading to increase of bandgap and deep‐blue emission. In addition, hydrogen bonds between the hydroxy groups of silane molecules and halide anions in perovskite can suppress ion migration for improving emission stability. As a result, an optimal PeLED is developed with deep‐blue emission at 458 nm and excellent color stability, which yields an EQE and luminance of 1.1% and 130 cd m−2, respectively, representing a state‐of‐the‐art result for thin‐film PeLEDs in this emission region. This work paves the way to achieve high‐performance deep‐blue PeLEDs with stable emissions to meet the demand for potential applications such as full‐color display.
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