Generalized Einstein relation for disordered semiconductors - implications for device performance

The ratio between mobility and diffusion parameters is derived for a Gaussian-like density of states. This steady-state analysis is expected to be applicable to a wide range of organic materials (polymers or small molecules) as it relies on the existence of quasi-equilibrium only. Our analysis shows that there is an inherent dependence of the transport in trap-free disordered organic-materials on the charge density. The implications for the contact phenomena and exciton generation rate in light emitting diodes as well as channel-width in field-effect transistors is discussed

Nanoparticulate Metal Oxide Top Electrode Interface Modification Improves the Thermal Stability of Inverted Perovskite Photovoltaics

Solution processed {\gamma}-Fe2O3 nanoparticles via the solvothermal colloidal synthesis in conjunction with ligand-exchange method are used for interface modification of the top electrode in inverted perovskite solar cells. In comparison to more conventional top electrodes such as PC(70)BM/Al and PC(70)BM/AZO/Al, we show that incorporation of a {\gamma}-Fe2O3 provides an alternative solution processed top electrode (PC(70)BM/{\gamma}-Fe2O3/Al) that not only results in comparable power conversion efficiencies but also improved thermal stability of inverted perovskite photovoltaics. The origin of improved stability of inverted perovskite solar cells incorporating PC(70)BM/ {\gamma}-Fe2O3/Al under accelerated heat lifetime conditions is attributed to the acidic surface nature of {\gamma}-Fe2O3 and reduced charge trapped density within PC(70)BM/ {\gamma}-Fe2O3/Al top electrode interfaces.Comment: 24 pages, 11 figure

Preventing Hysteresis in Perovskite Solar Cells by Undoped Charge Blocking Layers

Preventing hysteresis in lead halide perovskite solar cells remains one of the key challenges hindering their integration into industrial applications. Herein, we numerically study a model solar cell system that is based on a mixed electron–ion conducting perovskite active layer and vary the configuration of undoped charge-blocking layers within the device. We find that the use of undoped blocking layers significantly reduces the potential drop across the perovskite active layer. This redistribution of voltage across the device suppresses the ion accumulation, or deficiency, which would otherwise develop at the two ends of the active layer. The fill factor is not compromised, provided that the blocking layers’ mobility value is not lower than 0.01 cm² V^–1 s^–1, which results in devices with power-conversion efficiencies surpassing 20% and minimal hysteresis. We believe that this method not only can suppress hysteresis effectively but could also contribute to the long-term stability of such cells that have been shown to be adversely affected by ion migration