No abstract

Straightforward evidence for ion‐diffusion‐induced interfacial degradation in inverted perovskite solar cells is presented. Over 1000 h, solar cells inevitably undergo degradation, especially with respect to the current density and fill factor. The Ag electrode is peeled off and re‐evaporated to investigate the effect of the Ag/[6,6]‐phenyl C71 butyric acid methyl ester (PCBM) interfacial degradation on the photovoltaic performance at days 10 (240 h), 20 (480 h), 30 (720 h), and 40 (960 h). The power conversion efficiency increases after the Ag electrode restoration process. While the current density shows a slightly decreased value, the fill factor and open‐circuit voltage increase for the new electrode devices. The decrease in the activation energy due to the restored Ag electrode induces recovery of the fill factor. The diffused I− ions react with the PCBM molecules, resulting in a quasi n‐doping effect of PCBM. Upon electrode exchange, the reversible interaction between the iodine ions and PCBM causes current density variation. The disorder model for the open‐circuit voltage over a wide range of temperatures explains the open‐circuit voltage increase at every electrode exchange. Finally, the degradation mechanism of the inverted perovskite solar cell over 1000 h is described under the proposed recombination system.

A review towards the commercialization of colloidal quantum dot solar cells.

Low operational lifetime is a critical issue in perovskite light-emitting diodes. The forward-bias currents for light emission accelerate device degradation, which needs to be identified and understood to be able to improve the device stability. Here, we systematically analyze the degradation mechanism of perovskite lightemitting diodes (PeLEDs) fabricated with a sequential deposition method that produce a compact and pinhole-free perovskite film. The device exhibits an efficient green electroluminescence (peak wavelength at 533 nm and full width at half-maximum of 22 nm) with a maximum luminance of more than 67 000 cd/m 2 . The lifetime, however, is quite short; under the constant current bias for an initial luminance of 1000 cd/ m 2 , the decay time to reach half of the initial luminance is approximately 13 min. Dark spots are created and enlarged as a result of perovskite film deterioration and ion migration. By investigating morphological changes in the perovskite films and the amount of ion accumulation under the Al electrode for the unoperated, T 50 (luminance decay to 50% of the initial value), and T 10 (luminance decay to 10% of the initial value) devices, we propose a degradation mechanism for PeLEDs. The ion migration from the perovskite layer experienced electrochemical interactions with the Al electrode, causing device degradation.

Cellulose nanocrystals were preparedviashort-time pretreatment by electron-beam irradiation in the solid state and disintegration using high pressure homogenization.