摘要
High-efficiency solar cells often require light absorbers prepared from alloys, such as Cd Te_(1-x)Se_(x),CuIn_(x)Ga_(1-x)Se_(2), Cu_(2)ZnSnS_(4-x)Se_(x), and(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3). However, how alloying affects solar cell performance is poorly understood, and determining common features associated with alloying is of significant interest. Herein, we studied the correlation between the A/X site compositional ratio and the photogenerated carrier dynamics using mixed halide perovskites(Cs_(x)FA_(1-x))Pb(I_(1-y)Br_(y))_(3)as examples.Nonadiabatic molecular dynamics calculations demonstrated that charge carrier recombination is highly sensitive to the compositional ratio at the A/X-site. The enhanced lifetime is attributable to the suppression of atomic fluctuations, the weakening of electron-phonon coupling, and a reduction in the electrontransition probability between band edges. The optimal Br concentration was determined to be ~18%, in agreement with experimental observations. This study not only advances our understanding of why mixed perovskites usually exhibit superior experimental photoelectric properties, but also provides a route for optimizing the carrier lifetimes and efficiencies of perovskite solar cells.
基金
support from the National Key Research and Development Program of China(2020YFB1506400)
the National Natural Science Foundation of China (11974257)
Jiangsu Distinguished Young Talent Funding (BK20200003)
the Yunnan Provincial Key S&T Program(202002AB080001-1)
the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
support from the China Postdoctoral Science Foundation (2020M671570)。