Hot-injection has become the most widespread method used for the synthesis of perovskite quantum dots (QDs) with enormous interest for application in optoelectronic devices.

We fabricated perovskite quantum dot solar cells (PQDSCs) and varied the thickness of the QD layer by controlling the number of deposition cycles; the cells were systematically investigated with impedance spectroscopy. Despite the evident structural differences with respect to standard perovskite solar cells (PSCs), similar impedance spectra were obtained for PQDSCs, pointing to similar working principles in terms of the active layer. We distinguish two different regimes: At low illumination, recombination is ruled by multiple trapping with trap distributions and/or shunting. However, at higher light intensities, Shockley−Read−Hall recombination is observed. In addition, the low-frequency capacitance, C LF , of PQDSCs increases several orders of magnitude when the illumination is varied from dark to 1-sun conditions. This feature has not been observed in other kinds of photovoltaic devices and is characteristic of PSCs. Although there is no consensus about the exact mechanism responsible for C LF , the suggested models point to an ion migration origin. Its observation in thin-film and PQDSCs devices implies a similar effect in both.

Perovskite light-emitting diodes (PeLEDs) have emerged as a promising candidate for next-generation display technology and lighting applications owing to their high current efficiency, low operating voltage, narrow spectral emission and tuneable emission colour. Keys to achieving efficient PeLEDs are, beside an emitter layer with high optical quality, negligible charge injection barrier between charge injecting layers (CILs) and an optimized thickness of these CILs for a controlled flow of charge carriers through the device. In this study, we systematically optimized hole transport layers (HTL) and electron transport layers (ETL) in PeLEDs employing CsPbI 3 quantum dots (QDs) as an emitter layer. We also investigated two bilayer cathodes (Liq/Ag and LiF/Al) with the various ETLs employed in our study and observed that 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T) as ETL improves the band alignment, leading to better electron injection. The improved electron/hole current balance results in ~63% higher external quantum efficiency (EQE) in PO-T2T based devices compared to PeLEDs employing other ETLs. In addition, we tracked the operational stability of the different devices observing a correlation with the EQE, where samples with higher EQE (PO-T2T based devices) also present the highest stable operation at elevated current densities.