Photovoltaic & Optoelectronic Device Group

Abstract:

Light-emitting devices (LEDs) with inorganic perovskite nanocrystals (PNCs) fabricated through the all-solution process have tremendous potential for new-generation illumination and displays on account of their large area and cost-effective manufacturing. However, the development of efficient solution-processed PNC LEDs remains challenge, which mainly results from the fact that only a few types of charge transport layers can be employed for the subsequent deposition steps, thus leading to injection barriers and charge injection imbalance inside these LEDs. Herein 4,4'-bis(carbazole-9-yl) biphenyl (CBP) is introduced as a dopant into the poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine) (TFB) hole transport layer (HTL), which efficiently modulates the mobility of charge carrier as well as the energy level of the HTL, resulting in the barrier-free injection of the charge carrier in the as-fabricated solution-processed PNC LEDs. Consequently, the luminance of red LEDs (688 nm) reaches 2990 cd m^-2, and the external quantum efficiency achieves 8.1%, which is the optimal performance for solution-processed PNC LEDs to date. Additionally, the turn-on voltage and roll-off have also been improved by the more balanced charge injection.

Abstract:

Mn ²⁺ ion doped 2D (PEA) ₂ PbBr ₄ perovskite nanocrystals with a high PLQY of 54% were synthesized using a crystallization method at room temperature, and efficient energy transfer from excitons to the Mn ²⁺ dopant was proven.

Abstract:

LED light bulbs that simulate solar spectrum were fabricated using CdSe core-shell quantum dots in combination with GaN blue-light chips. They exhibited excellent optical properties such as white CIE coordinates of (0.33, 0.33), high color rendering index (CRI) of 98 and correlated color temperature (CCT) of 5352 K. Moreover, a circuit system was used to control the LEDs so that the lighting spectrum changes with the time in a day to simulate the actual solar spectrum. The results show that the sun-like spectrum smart bulbs not only have good optical properties and high electrical stability, but also can automatically adjust their spectrum according to the time, making the lighting natural. This work makes sun-like lighting conditions for some special environments to promote the application of smart bulbs in smart lighting.