The operational stability of perovskite solar cells (PSCs) remains a limiting factor in their commercial implementation. We studied the long-term outdoor stability of ITO/SnO2/Cs0.05((CH3NH3)0.15(CH­(NH2)2)0.85)0.95PbI2.55Br0.45/spiro-OMeTAD/Au cells, as well as the dynamics of their degradation, under simulated sunlight indoors and their recovery in the dark. The extent of overall degradation was found to depend on processes occurring both under illumination and in the dark, i.e., during the daytime and nighttime, with the dynamics varying with cell aging. Full recovery of efficiency in the dark was observed for cells at early degradation stages. Further cell degradation resulted in recovery times much longer than one night, appearing as irreversible degradation under real operational conditions. At later degradation stages, very different dynamics were observed: short-circuit current density and fill factor exhibited a pronounced drop upon light turn-off but strong improvement under subsequent illumination. The interplay of reversible and irreversible degradation processes with different recovery dynamics was demonstrated to result in changes in the cell’s diurnal PCE dependence during its operational lifespan under real sunlight conditions.

Understanding degradation mechanisms in halide perovskite solar cells is the key aspect to achieve a breakthrough in photovoltaics.

We propose a new approach for assessing the lifetimes of perovskite photovoltaics based on daily energy output which accounts for reversible diurnal changes.

Perylenediimide/carbon nanotube films solution-fabricated in air were used as back contacts for CsPbBr3 solar cells resulting in excellent outdoor performance.

Degradation rates in perovskite solar cells (PSCs) were previously shown to be bias dependent; however, little is known about the mechanisms and driving factors that account for such degradation. Herein, stability studies under concentrated sunlight are demonstrated as a powerful experimental methodology to investigate bias-dependent PSC degradation mechanisms. Stress testing of encapsulated PSCs' stability shows that light intensity is more significant than the illumination dose for PSC degradation under short-circuit (SC) conditions, whereas the dose is the determining factor under open-circuit (OC) stressing. This indicates that different degradation mechanisms are dominant under different bias conditions. It is postulated that degradation at SC biasing is dominated by ion migration, facilitated by photogenerated defects. Degradation at OC biasing can be explained by photogenerated radicals acting as nonradiative recombination centers (charge traps), which are created via reactions with accumulated charge carriers. Trap formation upon OC biasing is in accordance with degradation of photoluminescence and OC voltage (V OC ) observed under this stress. A combination of multiple mechanisms, all with reduced driving forces compared with OC /SC biasing, explains degradation at maximum power point biasing. Understanding the bias effect on PSC stability can elucidate the underlying degradation mechanisms and lead to routes to reduce them.

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Morphology of the donor/acceptor network in the photoactive layer is critical in order to optimize the device performance. In the present study, new trihydrazone-functionalized cyanopyridine (CPTH-D16) demonstrating ambient temperature hexagonal columnar liquid crystalline phase is introduced into the well-known photoactive layer i.e. P3HT:PCBM as processing additive towards the construction of an efficient solar cell. Photon absorption and emission properties of the blends in solution/film state are systematically investigated by UVvisible and fluorescence spectroscopy. Further, surface morphology, degree of crystallinity, changes in nanostructure, and conductivity of the blend films are observed through epifluorescence and atomic force microscopy. It is observed that the addition of CPTH-D16 liquid crystal drastically increases the TUNA current passing throughout the P3HT:PCBM film. Here, the structural anisotropic nature of CPTH-D16 material helps to obtain well-ordered morphology with nanostructured crystallite formation as well as the enhanced current in the P3HT:PCBM film.

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