Optoelectronic Modulation of Undoped NiO_x Films for Inverted Perovskite Solar Cells via Intrinsic Defect Regulation

Abstract

Ni vacancy (V Ni ) as an intrinsic defect plays an important role in the optical and electronic properties of NiO x films for inverted planar perovskite solar cell (PSC) applications. This work presents a facile method to fabricate highly dense and continuous NiO x films with excellent optical transmittance and electronic conductivity by pulsed laser deposition. By simply adjusting the preparation parameters, including oxygen partial pressure, postannealing temperature, and duration time, the well-regulated V Ni defects contribute to the modified conductivity and optical transmittance of the NiO x films. The conductivity and optical transmittance of NiO x films are all dramatically enhanced with the increasing oxygen partial pressure. Specifically, the valence band level of NiO x is adjusted by the V Ni defect densities to better match or align with that of the perovskite layer for faster hole extraction with lower energy losses. Density functional theory calculation displays that the Fermi energy level is shifted to a lower energy level due to the enhanced hole carrier concentration generated from the increased V Ni . Benefiting from the excellent optical transmittance, electronic conductivity, and well-matched energy alignment, the inverted PSC with NiO x hole transport layer (HTL) exhibits the highest power conversion efficiency of 16.85% with high open-circuit voltage (1.14 V), short-circuit current density (20.49 mA/cm 2 ), fill factor (0.72), and negligible current−voltage hysteresis effect. This work reveals that modulating the intrinsic defects of NiO x HTLs is an efficient way to achieve high performance of NiO x -based inverted PSCs.

Heterostructure Silicon Solar Cells with Enhanced Power Conversion Efficiency Based on Six/Ni3+ Self-Doped NiOx Passivating Contact

“…The obtained optical band gaps of NiO x -3, NiO x -5, NiO x -10, and NiO x -15 samples are 3.55, 3.52, 3.51, and 3.46 eV, respectively, showing a decreasing trend with the increase in the oxygen flow rate. The calculated optical band gap of NiO x is consistent with the value from the other literature …”

“…However, Ni 2 O 3 is not stable at low temperatures in ambient air and easily binds the atmospheric hydroxyl groups and forms NiOOH during the transfer of the sample . Meanwhile, Ni 2 O 3 species will lead to the improved optical band gap, according to the reported literature. , Our experimental results show that the band gap decreases with the increase in the Ni 3+ ratio. Therefore, it is very likely that the Ni 3+ peaks in our work come from the NiOOH species.…”

“…28 Meanwhile, Ni 2 O 3 species will lead to the improved optical band gap, according to the reported literature. 25,29 Our experimental results show that the band gap decreases with the increase in the Ni 3+ ratio. Therefore, it is very likely that the Ni 3+ peaks in our work come from the NiOOH species.…”

“…The calculated optical band gap of NiO x is consistent with the value from the other literature. 25 XPS was used to analyze the effect of the F O2/Ar on the chemical components and electronic states of the NiO x film. As shown in Figure 2, the asymmetric Ni 2p 3/2 and Ni 2p 1/2 doublet cannot be detected within the detection limit, suggesting the absence of the metallic nickel in all the NiO x samples.…”

Metal oxide charge transporting layers for stable high-performance perovskite solar cells

“…[205][206][207][208][209] The electrical conductivity and transmittance of nickel oxide films are crucially controlled by partial oxygen pressure. 210 The valence band level of NiO X is 211 With variation in partial oxygen pressure during pulsed laser deposition of NiO X layer, its V Ni defect densities are modulated, which resulted in high J SC , V OC and PCE of 20.49 mA cm −2 , 1.14 V, 16.85% respectively (11 Pa partial oxygen pressure). In another work, post treatment on the NiO X layer before perovskite deposition aids in the removal of reactive Ni ≥3+ sites and prevents further reaction between NiO X and perovskite layers to help to achieve V OC and PCE values of 1.15 V and 20.1%, respectively.…”