Hanben Niu

Film-through large perovskite grains formation via a combination of sequential thermal and solvent treatment

Organic–inorganic halide perovskites have recently attracted strong research interest for fabrication of high-performance, low-cost photovoltaic devices. Recently, we reported a highly reproducible procedure to fabricate high-performance organic–inorganic halide perovskite solar cells. This procedure, based on a one-step, solvent-induced, fast deposition-crystallization method, involves the use of sec-butyl alcohol as a new solvent to induce the CH3NH3PbI3 fast crystallization deposition. In the present study, we propose a reproducible fabrication method to prepare both flat and large-grain perovskite film by adding a pre-annealing step to strengthen the perovskite nucleation, aiming to facilitate the excess CH3NH3I and solvent removal in the sec-butyl alcohol soaking process, in which all films with thickness between 420 nm and 1 μm performed uniformly. The best performing planar device obtained with this procedure had an efficiency of 17.2% under AM 1.5G illumination and an average power conversion efficiency of 16.2 ± 0.5%. We also analyzed the efficiency of halide perovskite planar solar cells as a function of the perovskite film thickness; the efficiency dropped only slightly to 15.7% when the perovskite film thickness was increased to 1 μm.

sec-Butyl alcohol assisted pinhole-free perovskite film growth for high-performance solar cells

Perovskites have recently emerged as promising materials for high-performance, low-cost photovoltaic devices. Here, we report a one-step, solvent-induced, fast crystallization method based on sec-butyl alcohol to produce flat, uniform CH3NH3PbI3 films. sec-Butyl alcohol has proven to be a suitable solvent not only for the CH3NH3PbI3 fast crystallization deposition process, but also for adjusting the amount of CH3NH3I in CH3NH3PbI3 films. Planar heterojunction solar cells with flat and pinhole-free CH3NH3PbI3 films yielded an average power conversion efficiency (PCE) of 13.1 ± 1.2% and the highest PCE of 14.3%; no hysteresis was observed by changing the scan direction in our devices under standard AM 1.5 illumination. Remarkably, we found that the presence of CH3NH3I in CH3NH3PbI3 films has a positive effect on the photovoltaic device performance.

Synthesis, characterization and application of starburst 9-alkyl-1,3,6,8-tetraaryl-carbazole derivatives for blue-violet to UV OLEDs

A series of starburst carbazole derivatives, which comprise various aryl groups appended to the 1,3,6,8-positions of a 9-alkyl-carbazole core, are synthesized and characterized. These compounds exhibit good thermal stabilities with glass transition temperatures up to 199 °C and thermal decomposition temperatures ranging from 321 to 485 °C. The starburst configuration of the as-prepared compounds results in fluorescence emission in the UV to blue-violet region (λmax = 389–409 nm) with photoluminescence quantum efficiency (ΦPL) reaching 90% and narrow full width half maximum (FWHM) of 43–54 nm in solution. Light-emitting devices are successfully fabricated using these materials as emitters, and emit UV to blue-violet light. With a device structure of indium tin oxide (ITO)/molybdenum trioxide (MoO3)/1,3,6,8-tetraaryl carbazole derivatives/1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI)/8-hydroxyquinoline aluminum (Alq3)/LiF/Al, maximum external quantum efficiency (EQEmax) of 2.05% and 3.4% have been obtained at UV wavelength of 394 nm with FWHM of 42 nm and blue-violet wavelength of 415 nm with FWHM of 46 nm, respectively.

Star-configured carbazole as an efficient near-ultraviolet emitter and hole-transporting material for organic light-emitting devices

A novel organic material, 9-methyl-1,3,6,8-tetraphenyl-carbazole (MTPC-Me), for use in organic electroluminescent devices has been developed. This star-configured carbazole gives a strong near-ultraviolet (n-UV) emission (λmax=389nm) with a high emission quantum efficiency of 47% and a narrow full width half maximum of 40nm. Two types of high-performance organic light-emitting devices were obtained using MTPC-Me as a n-UV emitter and hole-transporting material with maximum external quantum efficiency, brightness, and turn-on voltage of 1.2%, 1040cd∕m2, and 3.5V for the former and 1.1%, 18000cd∕m2, and 2.4V for the latter, respectively.