Copper Iodide Interlayer for Improved Charge Extraction and Stability of Inverted Perovskite Solar Cells

Abstract

Nickel oxide (NiO) is one of the most promising and high-performing Hole Transporting Layer (HTL) in inverted perovskite solar cells due to ideal band alignment with perovskite absorber, wide band gap, and high mobility of charges. At the same time, however, NiO does not provide good contact and trap-free junction for hole collection. In this paper, we examine this problem by developing a double hole transport configuration with a copper iodide (CuI) interlayer for efficient surface passivation. Transient photo-current (TPC) measurements showed that Perovskite/HTL interface with CuI interlayer has an improved hole injection; CuI passivation reduces the concentration of traps and the parasitic charge accumulation that limits the flow of charges. Moreover, we found that CuI protect the HTL/perovskite interface from degradation and consequently improve the stability of the cell. The presence of CuI interlayer induces an improvement of open-circuit voltage VOC (from 1.02 V to 1.07 V), an increase of the shunt resistance RSH (100%), a reduction of the series resistance RS (−30%), and finally a +10% improvement of the solar cell efficiency.

Robust Inorganic Hole Transport Materials for Organic and Perovskite Solar Cells: Insights into Materials Electronic Properties and Device Performance

“…[ 319 ] Saranin et al later reported the advantageous application of CuI as a HTL in p–i–n‐type (inverted) MAPbI 3 ‐based PSCs with a PCE of 14.23%. [ 320 ] Few other reports on CuI as the HTL in MAPbI 3 ‐based PSCs with PCEs of 14.7% [ 321 ] and 13.5% [ 322 ] have also appeared recently in the literature. Wang et al [ 323 ] adopted a simple solid–gas reaction method to deposit compact and uniform CuI films.…”

Progress in Perovskite Solar Cells towards Commercialization—A Review

“…CuI with a wide band gap of 3.1 eV were observed to improve the device stability due to its hydrophobic nature. Sun et al achieved the highest PCE of 16.8% using room-temperature and solution-processed CuI as HTL, and this device maintained more than 93% of its original PCE after 288 h of storage under 25% humidity and room temperature [ 142 ]. CuO x including Cu 2 O and CuO are typical p-type semiconductors and can work as attractive inorganic HTMs in PSCs due to their high conductivity, solution-processing, and suitable band levels ( Figure 8 a).…”

Simulating the Performance of a Formamidinium Based Mixed Cation Lead Halide Perovskite Solar Cell

“…Hörantner et al [ 53 ] have shown that long alkyl chained silane molecules can be used to block shunt pathways without obstructing the charge transfer of the solar cell devices, leading to the significant increase in the V oc values, while other inorganic materials can also be used as passivation materials. Saranin et al [ 54 ] report the use of copper (I) iodide, which has been usually applied as a hole transport layer, as an interlayer between the perovskite and the electron transport layer in their experiments; the inclusion of CuI increased the efficiency of the solar cell as well as their shelf-life stability.…”