Efficiency and stability enhancement of perovskite solar cells by introducing CsPbI3 quantum dots as an interface engineering layer

Although great efforts have been devoted to enhancing the efficiency and stability of perovskite solar cells (PSCs), the performance of PSCs has been far lower than anticipated. Interface engineering is helpful for obtaining high efficiency and stability through control of the interfacial charge transfer in PSCs. This paper demonstrates that the efficiency and stability of PSCs can be enhanced by introducing stable α-CsPbI3 quantum dots (QDs) as an interface layer between the perovskite film and the hole transport material (HTM) layer. By synergistically controlling the valence band position (VBP) of the perovskite and the interface layer, an interface engineering strategy was successfully used to increase the efficiency of hole transfer from the perovskite to the HTM layer, resulting in the power conversion efficiency increasing from 15.17 to 18.56%. In addition, the enhancement of the stability of PSCs can be attributed to coating inorganic CsPbI3 QDs onto the perovskite layer, which have a high moisture stability and result in long-term stability of the PSCs in ambient air. Researchers have used tiny inorganic crystals known as quantum dots to engineer improved moisture resistance and enhanced power conversion into low-cost solar cells. Perovskites, a family of crystals that includes methylammonium lead tri-iodide, can be easily assembled into photovoltaic devices that harvest sunlight nearly as well as silicon. Baomin Xu and Chun Cheng from China’s Southern University of Science and Technology, Shenzhen, and co-workers report a solar cell containing cesium–lead–iodine quantum dots inserted between a perovskite film and an organic conducting material. The dots introduce new electronic states that improve extraction of photogenerated charge. They also migrate through pores in the perovskite film to form a water-repelling surface layer. This strategy enabled the team to operate the device with high efficiency for over a month in humid conditions that normally degrade perovskite films. Due to the matching energy level of CsPbI3 quantum dots and perovskite layer, the efficiency of perovskite solar cells was substantially enhanced from 15.17% to 18.56% by introducing CsPbI3 quantum dots as interface engineering layer. Moreover, perovskite solar cells with CsPbI3 QDs maintained 82% of its initial performance for 30 days at over 30% RH without any encapsulation.