Manipulating SnO₂ Growth for Efficient Electron Transport in Perovskite Solar Cells

Abstract

binding energy, and high charge transport mobility. [1] The record power conversion efficiency of solar cells based on perovskite materials have recently reached up to 25.5%, [2] not far off traditional crystalline silicon solar cells.In a typical perovskite solar cell, the perovskite layer is sandwiched between a transparent electrode and a reflective back electrode, and electron transport layer (ETL) and hole transport layer are usually inserted between the perovskite and the electrodes to facilitate majority charge transport and to block minority charge carriers. The performance of perovskite solar cells is strongly related to the properties of the charge transport layers, especially the underneath layer on which the perovskite was cast, such as ETL in case of conventional n-i-p device architecture. In particular, the polarity of the substrates determines the nature of perovskite layer and specifically its doping state (n, p, or intrinsic) near the charge-extraction layers, [3] and the surface energy and morphology of the underneath layer affects the crystallization of the perovskite thin films. In addition, the interface issues in terms of interfacial nonradiative recombination and energy level alignment between the ETL and perovskite play an important role in the device performance, hysteresis phenomenon, and operational stability of the corresponding solar cells. [4] Furthermore, the optical constant of the underneath layer determines the light incidence and optoelectric field distribution. [5] Solution-processed tin oxide (SnO 2 ) is ubiquitously used as the electron transport layer (ETL) in perovskite solar cells, while the main concerns related to the application of SnO 2 nanoparticles are the self-aggregation potential and infeasible energy level adjustment, leading to inhomogeneous thin films and mismatched energy alignment with perovskite. Herein, a novel route is developed by adding a functional titanium diisopropoxide bis(acetylacetonate) (TiAcAc) molecule, comprising TiO 4 4core, functional CO, and long alkene groups, into the SnO 2 nanoparticle solution, to optimize the electronic transfer property of SnO 2 for efficient perovskite solar cells. It is found that the TiO 4 4can be used to tune the electronic property of the SnO 2 layer, and the long alkenes can act as a stabilizer to avoid the nanoparticle aggregation and electronic glue among the SnO 2 nanoparticles in the eventual nanoparticulate thin film, enhancing its homogeneity and conductivity. Furthermore, the residual CO groups on the ETL surface can strongly associate with the Pb 2+ and improve the interface intimacy between the ETL and perovskite. As a result, the efficiency of perovskite solar cells can be boosted from 18% to above 20% with significantly reduced hysteresis by employing SnO 2 -TiAcAc as electron transport layer, indicating a great potential for efficient perovskite solar cells.

Advances in SnO2 for Efficient and Stable n–i–p Perovskite Solar Cells

“…[79] In addition, the surface state of SnO 2 can affect the reaction between SnO 2 and perovskite precursor related to the mechanical integrity of SnO 2 /perovskite interfaces and perovskite crystal growth. [80][81][82] In this section, we discuss several key aspects of the SnO 2 /perovskite interface, with a focus on the n-i-p device configuration.…”

Amino‐Functionalized Niobium‐Carbide MXene Serving as Electron Transport Layer and Perovskite Additive for the Preparation of High‐Performance and Stable Methylammonium‐Free Perovskite Solar Cells

“…[5,6] The commonly used ETLs such as titanium dioxide (TiO 2 ) and tin dioxide (SnO 2 ) have their disadvantages including high preparation temperature, spontaneous aggregation of nanoparticles, and poor bending resistance in the mass production of large-area and flexible devices. [7][8][9] Therefore, the development of new ETL materials with good optoelectrical properties and energy level matching the perovskite layer is essential for the preparation of large-area and flexible PVSCs.…”

Electron transport layer assisted by nickel chloride hexahydrate for open-circuit voltage improvement in MAPbI3 perovskite solar cells

“…33,34 Compared with FTO/SnO 2 , FTO/SnO 2 -NiCl 2 lms were denser, and Ni 2+ had the effect of antireection, which promoted the increase of transmittance of FTO/SnO 2 -NiCl 2 lms in the visible region. 35,36 Fig. 1a and b show the SEM images of the SnO 2 lms without and with NiCl 2 , respectively.…”