Efficient Perovskite Solar Cells with a CuI-Modified Polymer Hole-Transport Layer

Abstract

Poly­[bis­(4-phenyl)­(2,4,6-trimethylphenyl)­amine] (PTAA) is one of the most used polymer hole-transport layers in inverted perovskite solar cells (PVSCs). However, due to the poor crystal quality of perovskite films prepared on the PTAA underlayer, the solar cells with the PTAA hole-transport layer have not shown excellent photoelectric performance. Furthermore, as a polymer semiconductor material, PTAA is highly hydrophobic, and the wettability of the perovskite precursor solution on the surface of PTAA is not very good, affecting the crystal quality of the perovskite film. CuI has not only a suitable energy-level structure and excellent charge transfer efficiency but also the same element iodine as perovskite, which is conducive to the formation of good interface contact. In this paper, a PTAA film is modified with CuI, which not only improves the wettability but also promotes the crystallization of the perovskite film. A method is developed to estimate the deep defect density from transient open-circuit voltage decay. Using this method, we compare the density of deep-level traps of the perovskite active layer on a CuI-modified PTAA film with that on a PTAA film. We demonstrate that CuI modification to PTAA can inhibit both shallow defects and deep defects, which facilitates carrier transport effectively. The power conversion efficiency (PCE) of the CuI-modified devices achieves 20.20%, which is significantly higher than the 18.07% of the PTAA-only devices. This study demonstrates that the inorganic semiconductor material CuI-modified polymer hole-transport layer is an approach that would provide guidance for interface modification engineering of PVSCs.

Buried Interface‐The Key Issues for High Performance Inverted Perovskite Solar Cells

“…Inorganic CuI and GO were also used to obtain a good interface contacts and efficient carrier transport between PTAA or PEDOT:PSS and perovskite, respectively, considering their suitable energy-level structure and excellent charge transfer capability. [244,245] Particularly, the above discussed surface passivation for NiO x could also effectively improve the work function to reduce energy loss. Wu et al implemented NiO x /PTAA bilayer to optimize the energy level alignment at NiO x /perovskite interface (Figure 8c), resulting the improved PCE and V OC .…”

Critical Review of Cu‐Based Hole Transport Materials for Perovskite Solar Cells: From Theoretical Insights to Experimental Validation

“…After the incorporation of CuI, a significant reduction in defect density was observed, which resulted in a device PCE of 20.20%, significantly higher than the 18.07% PCE of the pure PTAA. [ 152 ] In this CuI/PTAA composite HTM, CuI enhances the wetting properties of the PTAA layer, while PTAA improves the charge extraction property of the composite HTM layer due to its superior photoelectric performance. Therefore, both the film quality and the charge extraction property of this composite HTM improve compared to their individual counterparts.…”

Recent Progress of Inorganic Hole‐Transport Materials for Perovskite Solar Cells†

“…Top view SEM images of perovskite films on (a) PTAA and (b) PTAA/CuI. [ 79 ] (c) Crystal structure of Cu(Tu)I. Hydrogen atoms have been omitted for clarity. [ 83 ] (d) Admittance spectra of the reference PSCs and the devices with CuI or Cu(Tu)I treatments, measured at temperature between 230 and 300 K with a step of 10 K. [ 83 ] (e) Schematic illustration of possible mechanism for the trap state passivation.…”

“…Figure 6 Top view SEM images of perovskite films on (a) PTAA and (b) PTAA/CuI [79]. (c) Crystal structure of Cu(Tu)I. Hydrogen atoms have been omitted for clarity [83].…”