Stability Improvement of Perovskite Solar Cells for Application of CuInS2 Quantum Dot-Modified TiO2 Nanoarrays

The construction of a three-dimensional donor/acceptor interface based on a bilayered titanium dioxide nanorod array-flower for perovskite solar cells

Recently, organic-inorganic hybrid perovskite solar cells have been considered as the new generation of photovoltaic devices due to their excellent performance. However, their finite interfacial stability limits their further commercialization. How to improve their stability is one of the important issues in current scientific research. Herein, a bilayered titanium dioxide nanorod array-flower (B-TiO₂-NAF) was prepared as an electron transport material for hybrid perovskite solar cells in order to overcome this difficulty. A device based on B-TiO₂-NAF exhibits an excellent power conversion efficiency (PCE) of 21.8% due to its low electron trap density (n_trap), low carrier recombination resistance (R_s), facilitated electron injection, and reduced nonradiative recombination rate. The application of B-TiO₂-NAF provides a stable three-dimensional (3-D) D/A interface and shortens the internal photoexciton diffusion distance. As a result, the device shows excellent long-term stability, which is maintained at over 83% of the initial efficiency after 30 days. Our work should be beneficial for the preparation of 3-D semiconductor materials and provides new insights into highly stable perovskite solar cells.

Application of Quantum Dot Interface Modification Layer in Perovskite Solar Cells: Progress and Perspectives

Perovskite solar cells (PSCs) are currently attracting a great deal of attention for their excellent photovoltaic properties, with a maximum photoelectric conversion efficiency (PCE) of 25.5%, comparable to that of silicon-based solar cells. However, PSCs suffer from energy level mismatch, a large number of defects in perovskite films, and easy decomposition under ultraviolet (UV) light, which greatly limit the industrial application of PSCs. Currently, quantum dot (QD) materials are widely used in PSCs due to their properties, such as quantum size effect and multi-exciton effect. In this review, we detail the application of QDs as an interfacial layer to PSCs to optimize the energy level alignment between two adjacent layers, facilitate charge and hole transport, and also effectively assist in the crystallization of perovskite films and passivate defects on the film surface.

Application of quantum dots in perovskite solar cells

Perovskite solar cells (PSCs) are important candidates for next-generation thin-film photovoltaic technology due to their superior performance in energy harvesting. At present, their photoelectric conversion efficiencies (PCEs) are comparable to those of silicon-based solar cells. PSCs usually have a multi-layer structure. Therefore, they face the problem that the energy levels between adjacent layers often mismatch each other. Meanwhile, large numbers of defects are often introduced due to the solution preparation procedures. Furthermore, the perovskite is prone to degradation under ultraviolet (UV) irradiation. These problems could degrade the efficiency and stability of PSCs. In order to solve these problems, quantum dots (QDs), a kind of low-dimensional semiconductor material, have been recently introduced into PSCs as charge transport materials, interfacial modification materials, dopants and luminescent down-shifting materials. By these strategies, the energy alignment and interfacial conditions are improved, the defects are efficiently passivated, and the instability of perovskite under UV irradiation is suppressed. So the device efficiency and stability are both improved. In this paper, we overview the recent progress of QDs' utilizations in PSCs.

Preparation of Low Grain Boundary Perovskite Crystals with Excellent Performance: The Inhibition of Ammonium Iodide

For the study, we prepared a low grain boundary three-dimensional CH3NH3PbI3 crystal (3D-MAPbI3) on TiO2 nanoarrays by inhibition of ammonium iodide and discussed the formation mechanism of the crystal. Based on the 3D-MAPbI3 crystal, solar cells showed modified performance with a power conversion efficiency (PCE) of up to 19.3%, which increases by 36.8% in contrast to the counterparts. We studied the internal photocurrent conversion process. The highest external quantum efficiency is up to 92%, and the electron injection efficiency is remarkably facilitated where the injection time decreases by 37.8% compared to the control group. In addition, based on 3D-MAPbI3, solar cells showed excellent air stability, which possesses 78.3% of the initial PCE, even though they were exposed to air for 30 days. Our results demonstrate a promising approach for the fabrication of perovskite solar cells with high efficiency and stability.

Performance of WO3-Incorporated Carbon Electrodes for Ambient Mesoscopic Perovskite Solar Cells

The stability of perovskite solar cells (PSC) is often compromised by the organic hole transport materials (HTMs). We report here the effect of WO₃ as an inorganic HTM for carbon electrodes for improved stability in PSCs, which are made under ambient conditions. Sequential fabrication of the PSC was performed under ambient conditions with mesoporous TiO₂/Al₂O₃/CH₃NH₃PbI₃ layers, and, on the top of these layers, the WO₃ nanoparticle-embedded carbon electrode was used. Different concentrations of WO₃ nanoparticles as HTM incorporated in carbon counter electrodes were tested, which varied the stability of the cell under ambient conditions. The addition of 7.5% WO₃ (by volume) led to a maximum power conversion efficiency of 10.5%, whereas the stability of the cells under ambient condition was ∼350 h, maintaining ∼80% of the initial efficiency under light illumination. At the same time, the higher WO₃ concentration exhibited an efficiency of 9.5%, which was stable up to ∼500 h with a loss of only ∼15% of the initial efficiency under normal atmospheric conditions and light illumination. This work demonstrates an effective way to improve the stability of carbon-based perovskite solar cells without affecting the efficiency for future applications.