Lead-free perovskite infrared light-emitting diodes are achieved by using a halide perovskite CsSnI as an emissive layer. The film shows compact micrometer-sized grains with only a few pinholes and cracks at the grain boundaries. The device exhibits maximum radiance of 40 W sr m at a current density of 364.3 mA cm and maximum external quantum efficiency of 3.8% at 4.5 V.

Through the incorporation of various halogen‐substituted chiral organic cations, the effects of chiral molecules on the chiroptical properties of hybrid organic–inorganic perovskites (HOIPs) are investigated. Among them, the HOIP having a Cl‐substituted chiral cation exhibits the highest circular dichroism (CD) and circular polarized luminescence (CPL) intensities, indicating the existence of the largest rotatory strength, whereas the F‐substituted HIOP shows the weakest intensities. The observed modulation can be correlated to the varied magnetic transition dipole of HOIPs, which is sensitive to the d‐spacing between inorganic layers and the halogen–halogen interaction between organic cations and the inorganic sheets. These counteracting effects meet the optimal CD and CPL intensity with chlorine substitution, rendering the rotatory strength of HOIPs arranged in the order of (ClMBA)2PbI4>(BrMBA)2PbI4>(IMBA)2PbI4>(MBA)2PbI4>(FMBA)2PbI4.

Articles you may be interested inHigh output current in vertical polymer space-charge-limited transistor induced by self-assembled monolayer Appl. Phys. Lett. 101, 093307 (2012); 10.1063/1.4748284High-performance space-charge-limited transistors with well-ordered nanoporous aluminum base electrode Appl. Phys. Lett. 99, 093306 (2011); 10.1063/1.3632045 Space-charge limited conduction in doped polypyrrole devicesA metal grid is sandwiched between poly͑3-hexylthiophene͒ to form a solid-state version of vacuum tube triode, where the vertical space-charge-limited current is modulated by the grid potential. The Al grid contains random submicron openings formed by a nonlithographic method. The multilayer polymer structure is made by spin coating. The operating voltage of the polymer space-charge-limited transistor is 3 V, and the current gain of 506 is obtained. The characteristics of the transistor can be tuned by the diameters and the density of the openings on the grid. Similar to the vacuum tube triode, the current follows a power law voltage dependence.

Perovskite white light-emitting diodes with only a single emissive layer were realized with CIE chromaticity coordinates of (0.3, 0.49).

The microscopic states and performance of organic solar cell are investigated theoretically to explore the effect of the carrier mobility. With Ohmic contacts between the semiconductor and the metal electrodes there are two origins of carriers in the semiconductor: the photocarriers generated by photon absorption and the dark carriers diffused from the electrodes. The power efficiency of the solar cell is limited by the recombination of a carrier with either the photocarrier or a dark carrier. Near the short-circuit condition the photocarrier recombination in the semiconductor bulk decreases as the mobility increases. Near the open-circuit condition the dark carrier recombination increases with the mobility. These two opposite effects balance with one another, resulting in an optimal mobility about 10 −2 cm 2 / V s which gives the highest power conversion efficiency. The balance of the electron and hole mobilities are not necessary to maintain the optimal efficiency also because of the balance of the photocarrier and dark carrier recombination. The efficiency remains about the same as one carrier mobility is fixed at 10 −2 cm 2 / V s while the other one varies from 10 −1 to 10 −3 cm 2 / V s. For solar cell with a Schottky barrier between the semiconductor and the metal electrode there is no dark carrier recombination. The efficiency therefore always increases with the mobility.