Highlights of this article
1. Discussed the important issues that need to be solved in the future development of flexible perovskite solar cells: Mechanical stability and water and oxygen resistance stability.
2. Discussed the flexible perovskite solar cellroll-to-roll large-scale manufacturing technology.
3. Discussed how to achieve this bybalancing the transmittance and conductivity of flexible transparent electrodes Key technologies for high-efficiency flexible perovskite solar cells.
Brief introduction
Professor Wang Mingkui’s research group at Wuhan National Research Center for Optoelectronics, Huazhong University of Science and Technology reviewed the development trends and core issues of high-performance flexible perovskite photovoltaic devices in recent years, focusing on the impact The mechanism of mechanical stability of flexible perovskite photovoltaic devices and its effective improvement methods. This work details the latest research progress of flexible perovskite photovoltaic devices, including internal stress engineering, grain boundary modification, self-healing strategies and crystallization control. At the same time, the challenges faced by flexible perovskite photovoltaic devices in terms of water and oxygen stability and packaging technology are also analyzed.
Graphical guide
I Advantages and industrialization prospects of flexible perovskite cells
Roll-to-roll manufacturing technology is an effective method for large-scale manufacturing of large-area F-PSCs. The roll-to-roll manufacturing process can produce F-PSCs quickly and at low cost, making it suitable for various wearable electronic products, portable power supplies and other fields. Flexible substrates have an important impact on the lightweight and flexibility of perovskite structural devices. Currently, the power-to-weight ratio of battery devices based on ultra-thin flexible substrates can reach up to 23W g⁻¹, which is much higher than the power-to-weight ratio of existing power generation devices. It can be seen that flexible F-PSCs will become the key to the development of overall flexible self-powered electronic products, large-scale photovoltaic integrated buildings, wearable photovoltaics, vehicle-mounted photovoltaics, and space and aerospace applications.
Figure 1. (a) Schematic diagram of F-PSCs manufactured by roll-to-roll process; (b) Power-to-mass ratio of different types of solar cells; (c) Rigid/flexible PSCs and commercial applications Comparison of c-Si device efficiency and corresponding lifetime.
II Core issues faced in the application of flexible perovskite batteries
The industrial application of F-PSCs still faces many problems: (1) The problem of insufficient bending resistance of the perovskite light-absorbing layer; (2) The problem of mismatch between the transmittance and conductivity of the flexible transparent electrode; (3) ) Device packaging methods and key packaging material selection issues.
Compared with rigid devices, F-PSCs still have a large gap in bending durability and environmental stability. The low crystallinity of perovskites is usually attributed to the existence of a large number of grain boundaries, which generate deep energy level defect states in semiconductors, leading to increased carrier recombination and performance degradation. Similarly, there are a large number of defects in flexible perovskite films, especially at grain boundaries, which reduces the mechanical stability and reliability of F-PSCs. Relevant researchers introduced polymerizable organic molecules into the crystallization of perovskite films, and promoted the in-situ polymerization of the molecules at the grain boundaries through photopolymerization, effectively passivating defects at the grain boundaries and improving its mechanical stability. In addition, the dimensional engineering control strategy induces the in-situ formation of two-dimensional perovskite across grain boundaries on the surface of the perovskite film, which can greatly improve the bending stability of the device.
Figure 2. (a) Crystal model at the grain boundary of a perovskite film; (b) In-situ polymerization of cross-linked [6,6]-phenyl C61 butoxetane ester (C-PCBOD) at the grain boundary ; (c) Spatial distribution of defect density in a perovskite film after bending cycles; (d) Schematic diagram of grain boundary modification of two-dimensional perovskite on a three-dimensional perovskite surface based on induced growth of water molecules; (e) Average Young's modulus of 3D MHP, 2-BBAI and 4-BBAI films; (f) Schematic diagram of two-dimensional perovskite improving the bending resistance of F-PSCs.
III Flexible electrode materials for perovskite batteries
In addition to the mechanical stability of F-PSCs being related to the bending resistance of the perovskite light-absorbing layer, transparent electrodes with high conductivity are crucial to improving the stability and photoelectric performance of F-PSCs. Transparent conductive oxides (TCOs), conductive polymers, carbon nanomaterials, and metal nanostructures are widely used as transparent electrodes for F-PSCs. Transparent ITO electrodes are commonly used in F-PSCs due to their excellent optoelectronic properties. However, due to the mechanical deformation process of the flexible substrate, ITO often cracks, thus affecting its conductivity and transmittance. To this end, high conductivity and high flexibility metal conductive networks and metal nanowires are introduced into F-PSCs to match the transmittance and conductivity of transparent electrodes and significantly improve the device's bending resistance.