Within recent years, metal halide perovskite solar cells (PSCs) attracted enormous attention in research and industries as a future sustainable technology to harvest solar energy at very low cost. The material has demonstrated outstanding optoelectronic properties as well as the tunability of the perovskite bandgap over a wide range of energies by compositional engineering of the crystal structure. These properties enable Perovskite-Perovskite multijunction solar cells (PSK-PSK MJ SCs), which can harvest a wide range of the sun spectrum at very high efficiencies. These aspects bring an outstanding research quality to focus on resolving the obstacles in scaling up this tremendous photovoltaic devices. To date, PSK-PSK MJ SCs technology is limited by the low performance and the instabilities of low bandgap (LBG) PSCs. In this project, this key challenge will be tackled by following approaches as the innovation aspects of the project : a) chemical engineering of the perovskite composition both in 3D and 2D as well as the 2D/3D perovskite microstructures b) novel approaches in protecting the Sn from oxidation in the perovskite compositions using the new reducing agents, and c) fabricating the efficient and stable LBG PSCs with an optimal perovskite composition, appropriate ETLs and HTLs, and optical modification of the devices which will enable a PSK-PSK MJ SC with power conversion efficiency (PCE) of >27% and >100 hours of stable power output. So far, by compositional engineering the Sn-based perovskite layers, a promising enhancement in the stability was reported. The fabricated perovskite multijunction using the reported 1.25eV LBG perovskite and 1.8 eV WBG perovskite showed an interesting 23% efficiency. In this regard, by adjusting the LBG perovskite structure (with novel 2D/3D compositional engineering of the perovskite) and choosing an appropriate WBG perovskite in the range of 1.6-1.8 eV as well as optical engineering of the device architecture, the PCE of >27% and >100 hours would be achievable.
The key challenge of PSK-PSK MJ photovoltaics is the lack of a stable and high efficiency LBG perovskite bottom solar cell. In this project, this challenge will be tackled by researching and developing LBG perovskites of 2D/3D and stable perovskite structure. The overarching targets are I) developing an efficient and stable 2D/3D LBG PSCs II) employing the stable and efficient LBG PSCs in a PSK-PSK MJ SC with PCE of >27% and >100 hours of stable power output. This project will reach these targets along the research objectives outlined below:
a) Engineering Low Bandgap PSCs with Bandgap of 1.1 - 1.3 eV.
b) Demonstrating High Efficiency in LBG PSCs.
c) Demonstrating High Stability in LBG PSCs.
d) Prototype of PSK-PSK MJ SCs.
