Simulation-guided Design and Fabrication of High-performance Perovskite/Organic Tandem Solar Cells

To tackle the daunting challenges of increasing global energy demand and achieving carbon neutrality simultaneously to preserve the environment, it is imperative to develop a viable solution that combines the development of novel materials and scalable processing methods to produce clean energy. The emergence of both solution-processed organic and metal halide perovskite semiconductors and their derived solar cells has the potential to transform the landscape of photovoltaic technology in delivering scalable and high-performance solar cells to provide sustainable green energy. While the power conversion efficiencies (PCEs) of both single-junction organic solar cells (OSCs) and perovskite solar cells (PSCs) are rapidly ascending to >19% and >25%, respectively, their maximum efficiency is limited to ~30% accordingly to the Shockley-Queisser model for single-junction devices. However, it is possible to significantly increase the efficiency of solar cells to over 40% by constructing a multi-junction (or tandem) device that consists of multiple light absorbers with considerably different bandgaps to reduce the overall transmission and thermalization losses of the solar cells.In this project, we will develop high-performance monolithic perovskite/organic tandem solar cells (TSCs) comprising a wide bandgap (WBG) perovskite front cell and a narrow bandgap (NBG) organic rear cell connected through a recombination junction. The WBG (Eg: 1.7-1.85 eV) PSCs are chosen for the front cell due to their strong and broad absorption for visible light, smaller voltage loss, and higher photoresponse when compared to their organic counterparts with approximate bandgap. While NBG (Eg: 1.1-1.25 eV) OSCs can potentially offer better near-infrared absorption tunability and stability compared with the Sn-based NBG perovskites, making them favorable candidates for the rear cell of the tandem cells. Moreover, the advantage of the perovskite and organic light absorbing layers being processed from orthogonal solvents imposes fewer constraints on the choice of the materials for constructing the recombination junction and provides better flexibility on the device design of TSCs. To demonstrate state-of-the-art perovskite/organic TSCs, an integrated strategy combining materials, interface, optical, and process engineering will be adopted to optimize the two subcells and the interconnect junction simultaneously. In addition, a comprehensive optoelectronic model will also be developed to simulate the electrical and optical properties of the TSCs and to provide guidelines to optimize their device performance. The successful implementation of this proposed project will have farreaching impacts on developing high-efficiency, low-cost and scalable TSC technology and will further pave the way for its commercialization.