Researchers from the Chinese Academy of Sciences (CAS), ShanghaiTech University, Zhejiang Laboratory and Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering recently reported an efficient (>27% reported efficiency) perovskite solar cell that uses a back mirror based on silver to improve light harvesting.
The ultrathin perovskite solar cell utilizes a Gires-Tournois resonator to improve light absorption - an optical standing-wave resonator designed for generating chromatic dispersion. Gires-Tournois resonators are usually based on a reflective metal mirror and are primarily used in chirping applications such as pulse compression. The structure of the resonator in this study had a simple optical structure, combined with a silver back mirror, to optimize light capture and utilization while improving light absorption capacity.
The researchers explained that they aimed to carefully design the thickness of each layer in the solar cell and ended up choosing silver for the reflective metal mirror after a series of simulations.
They cell has a 10 nm electron transport layer (ETL) based on zinc oxide (ZnO), a 45 nm perovskite absorber, a 5 nm hole transport layer (HTL) made of nickel(II) oxide (NiOx), and a 60 nm silver back mirror. The team tested the effectiveness of the proposed theoretical framework using optical simulation and SCAPS software analysis.
The proposed cell configuration, according to the research group, could achieve an average absorptivity of approximately 85%. This would be mainly due to an increase in light absorption in the wavelength range of 400-800 nm, which would result in a “significant” enhancement in the incident photon current efficiency (IPCE) attributable to “pronounced” light-matter interference effects between the perovskite absorber and the metal mirror.
According to the team, electrical simulations indicate that the ultrathin MAPbI3 perovskite solar cell boasts a photoelectric conversion efficiency up to around 26%, higher than its conventional counterparts, and under ideal conditions, the conversion efficiency of ultra-thin perovskite solar cells can even reach about 27%.
They added this kind of ultrathin perovskite cell requires the use of vacuum deposition techniques to achieve the desired efficiency levels in commercial production.
The team believes that this theoretical framework's successful formulation will be beneficial for the experimental progression of ultrathin perovskite solar cells.
