Dr zhongcheng yuan

Abstract:

Solar cells based on metal halide perovskites are one of the most promising photovoltaic technologies1,2,3,4. Over the past few years, the long-term operational stability of such devices has been greatly improved by tuning the composition of the perovskites5,6,7,8,9, optimizing the interfaces within the device structures10,11,12,13, and using new encapsulation techniques14,15. However, further improvements are required in order to deliver a longer-lasting technology. Ion migration in the perovskite active layer—especially under illumination and heat—is arguably the most difficult aspect to mitigate16,17,18. Here we incorporate ionic liquids into the perovskite film and thence into positive–intrinsic–negative photovoltaic devices, increasing the device efficiency and markedly improving the long-term device stability. Specifically, we observe a degradation in performance of only around five per cent for the most stable encapsulated device under continuous simulated full-spectrum sunlight for more than 1,800 hours at 70 to 75 degrees Celsius, and estimate that the time required for the device to drop to eighty per cent of its peak performance is about 5,200 hours. Our demonstration of long-term operational, stable solar cells under intense conditions is a key step towards a reliable perovskite photovoltaic technology.

Abstract:

Metal halide perovskites are emerging as promising semiconductors for cost-effective and high-performance light-emitting diodes (LEDs). Previous investigations have focused on the optimisation of the emissive perovskite layer, for example, through quantum confinement to enhance the radiative recombination or through defect passivation to decrease non-radiative recombination. However, an in-depth understanding of how the buried charge transport layers affect the perovskite crystallisation, though of critical importance, is currently missing for perovskite LEDs. Here, we reveal synergistic effect of precursor stoichiometry and interfacial reactions for perovskite LEDs, and establish useful guidelines for rational device optimization. We reveal that efficient deprotonation of the undesirable organic cations by a metal oxide interlayer with a high isoelectric point is critical to promote the transition of intermediate phases to highly emissive perovskite films. Combining our findings with effective defect passivation of the active layer, we achieve high-efficiency perovskite LEDs with a maximum external quantum efficiency of 19.6%.

Abstract:

We investigate the effect of commonly used solution-processed TiOx, SnO2 and ZnO interlayers on the perovskite film crystallization process. We find that the ZnO/perovskite interface can efficiently catalyze the perovskite crystallization even without thermal annealing.