Carrier transport layers of tin-based perovskite solar cells

Abstract

To avoid environmental pollution caused by lead, the tin-based perovskite solar cells have become a research hotspot in the photovoltaic field. Numerical simulations of tin-based perovskite solar cells are conducted by the solar cell simulation software, SCAPS-1D, with different electron transport layers and hole transport layers. And then the performances of perovskite solar cells are compared with each other and analyzed on different carrier transport layers. The results show that band alignment between the carrier transport layer and the perovskite layer are critical to cell performances. A higher conduction band or electronic quasi-Fermi level of electron transport layer can lead to a higher open circuit voltage. Similarly, a lower valence band or hole quasi-Fermi level of hole transport layer can also promote a higher open circuit voltage. In addition, when the conduction band of electron transport layer is higher than that of the absorber, a spike barrier is formed at the interface between the electron transport layer and perovskite layer. Nevertheless, a spike barrier is formed at the interface between the perovskite layer and the hole transport layer if the valence band of hole transport layer is lower than that of the absorber. However, if the conduction band of electron transport layer is lower than that of the absorber or the valence band of hole transport layer is higher than that of the absorber, a cliff barrier is formed. Although the transport of carrier is hindered by spike barrier compared with cliff barrier, the activation energy for carrier recombination becomes lower than the bandgap of the perovskite layer, leading to the weaker interface recombination and the better performance. Comparing with other materials, satisfying output parameters are obtained when Cd_0.5Zn_0.5S and MASnBr₃ are adopted as the electron transport layer and the hole transport layer, respectively. The better performances are obtained as follows: <i>V</i>_oc = 0.94 V, <i>J</i>_sc = 30.35 mA/cm², FF = 76.65%, and PCE = 21.55%, so Cd_0.5Zn_0.5S and MASnBr₃ are suitable carrier transport layer materials. Our researches can help to design the high-performance tin-based perovskite solar cells.