Abstract
Hybrid organic-inorganic perovskites are promising materials for the application in solar cells and light-emitting diodes. However, the basic current-voltage behavior for electrons and holes is still poorly understood in these semiconductors due to their mixed electronic-ionic character. Here, we present the analysis of space-charge-limited electron and hole currents in the archetypical perovskite methyl ammonium lead iodide (MAPbI3). We demonstrate that the frequency dependence of the permittivity plays a crucial role in the analysis of space-charge-limited currents and their dependence on voltage scan rate and temperature. Using a mixed electronic-ionic device model based on experimentally determined parameters, the current-voltage characteristics of single-carrier devices are accurately reproduced. Our results reveal that in our solution processed MAPbI3 thin films transport of electrons dominates over holes. Furthermore, we show that the direction of the hysteresis in the current-voltage characteristics provides a fingerprint for the sign of the dominant moving ionic species.
Highlights
Hybrid organic-inorganic perovskites are promising materials for the application in solar cells and light-emitting diodes
space-charge-limited currents (SCLCs) are observed in so-called electron- and holeonly devices, in which, by careful choice of the electrodes, either only electrons or holes are injected into the semiconductor
We investigate SCLCs in singlecarrier devices of methylammonium lead iodide (MAPbI3), the work-horse material in perovskite solar-cell research
Summary
Hybrid organic-inorganic perovskites are promising materials for the application in solar cells and light-emitting diodes. Using a mixed electronic-ionic device model based on experimentally determined parameters, the current-voltage characteristics of single-carrier devices are accurately reproduced. A powerful technique that has proven its value in determining the time-averaged steady-state mobility of organic semiconductors is the measurement of space-charge-limited currents (SCLCs)[33,34]. There are numerous publications on SCLC measurements of perovskite single crystals and thin films, the effect of mobile ions, permittivity, and temperature on the current–voltage behavior are missing[7,19,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54]. We develop a drift-diffusion model, including experimentally validated ion dynamics that can consistently reproduce the scan-rate dependence and temperature dependence of the current–voltage characteristics of electron-only and hole-only devices. It is demonstrated that the direction of the hysteresis in the electron and hole currents reveals the sign of the dominant mobile ionic species
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