The certified efficiency of 1 cm2 scale all-perovskite tandem solar cells tends to lag behind that of their small-area (~0.1 cm2) counterparts. This performance deficit originates from inhomogeneity in wide-bandgap (WBG) perovskite solar cells (PSCs) at a large scale. The inhomogeneity is thought to be introduced at the bottom interface and within the perovskite bulk itself.
Researchers from Nanjing University, Jilin University, University of Cambridge, University of Victoria, The Australian National University, Chinese Academy of Sciences (CAS) and Renshine Solar (Suzhou) have reported an all-perovskite tandem solar cell based on a wide-bandgap top perovskite cell with a 20.5% efficiency.
In their recent work, the team uncovered another crucial source for the inhomogeneity – the top interface formed during the deposition of the electron transport layer (ETL, C60). Meanwhile, the poor ETL interface is also a significant limitation of device performance.
The scientists addressed this issue by introducing a mixture of 4-fluorophenethylamine (F-PEA) and 4-trifluoromethyl-phenylammonium (CF3-PA) to create a tailored two-dimensional perovskite layer (TTDL), in which F-PEA forms a two-dimensional perovskite at the surface reducing contact losses and inhomogeneity, CF3-PA enhances charge extraction and transport.
As a result, they demonstrated a high open-circuit voltage of 1.35 V and an efficiency of 20.5% in 1.77-eV WBG PSCs at a square centimeter scale. By stacking with a narrow-bandgap perovskite sub-cell, the scientists reported 1.05 cm2 all-perovskite tandem cells delivering 28.5% (certified 28.2%) efficiency, the highest among all reported so far.
This work showcases the importance of treating the top perovskite/ETL contact for upscaling perovskite solar cells. In addition, the technology will likely be further developed by Renshine Solar, a startup company founded by co-corresponding author Hairen Tan, that took part in this study.
