Interface Engineering to Eliminate Hysteresis of Carbon-Based Planar Heterojunction Perovskite Solar Cells via CuSCN Incorporation

Abstract

A carbon electrode with low cost and high stability exhibited competitiveness for its practical application in organic–inorganic hybrid perovskite solar cells (PSCs). Nonetheless, issues such as poor interface contact with an adjacent perovskite layer and obvious hysteresis phenomenon are bottlenecks that need to be overcome to make carbon-based PSCs (C-PSCs) more attractive in practice. Herein, we report an effective method to enhance the interfacial charge transport of C-PSCs by introducing the CuSCN material into the device. Two types of CuSCN-assisted devices were studied in this work. One was based on the deposition of an ultrathin CuSCN layer between the perovskite absorber layer and the carbon cathode (PSK/CuSCN/C), and the other was by infiltrating CuSCN solution into the carbon film (PSK/C-CuSCN) by taking advantage of the macroporous structure of the carbon. We have found that the CuSCN incorporation by both methods can effectively address the hysteretic feature in planar C-PSCs. The origin for the hysteresis evolution was unraveled by the investigation of the energy alignment and the kinetics of interfacial charge transfer and hole trap-state density. The results have shown that both types of CuSCN-containing devices showed improved interfacial charge carrier extraction, suppressed carrier recombination, reduced trap-state density, and enhanced charge transport, leading to negligible hysteresis. Furthermore, the CuSCN-incorporated C-PSCs demonstrated enhanced device stability. The power conversion efficiency remained 98 and 91% of the initial performance (13.6 and 13.4%) for PSK/CuSCN/C and PSK/C-CuSCN, respectively, after being stored under a high humidity (75–85%) environment for 10 days. The devices also demonstrated extraordinary long-term stability with a negligible performance drop after being stored in air (relative humidity: 33–35%) for 90 days.

An Approach to Quantify the Negative Capacitance Features in a Triple‐Cation based Perovskite Solar Cells

“…This difference is attributed to the presence of shallow trap states at the interfaces of the perovskite/charge selective layer interface. [40] The loss of electron generated by the weaker monochromatic light used in the EQE measurement at the perovskite/charge selective contact interface becomes severe as a consequence of the trapping process, while these trap states can be filled up under high illumination intensity as in the case of the J-V measurement, leading to the mismatch between two measurements. [41] To gain a deeper insight into the effect of the HTL on the charge (ions, electrons, and holes) transport and accumulation at the interfaces, we probed the fabricated PSCs by EIS.…”

Halide Perovskite Materials for Energy Storage Applications

“…[157] The presence of the ion diffusion often leads to hysteresis and unstable overall conversion efficiencies during the I-V measurement. [41,[158][159][160][161][162][163][164][165][166] The ion transports in halide perovskite materials is contributed by the point and extended defects (intrinsic). In addition, extrinsic factors such as light, heat, and electrical fields accelerate the ion transports.…”

Defect healingviaa gradient cooling strategy for efficient all-inorganic perovskite solar cells

“…It should be noted that no white light bias was exerted on the devices during EQE measurements to avoid the trap filling effect. 53 It was found that the gradient-cooled device exhibited larger EQE values compared to the quenched device, and the statistical distribution of EQE values at three typical wavelengths (400 nm, 500 nm, and 600 nm, Fig. S8, ESI †) demonstrated the reproducibility of this result.…”