Stability and Dark Hysteresis Correlate in NiO‐Based Perovskite Solar Cells

Abstract

for commercialization. [2,3] Thus, if metal halide perovskite (PSK) solar cells are to take part in supplying the world's energy demand, device stability must be significantly improved.Several kinds of stimuli have been found to degrade PSCs. When exposed to moist atmosphere, CH 3 NH 3 PbI 3 (MAPI) undergoes an irreversible degradation via the formation of hydrated phases. [4,5] Even the all-inorganic perovskite CsPbBr 3 undergoes intricate structural modifications when exposed to relative humidity (RH) above 60%, highlighting the sensitivity of lead halide perovskites to moisture also in the absence of organic cations. [6] Perovskites are also sensitive to atmospheric oxygen, which can rapidly diffuse inside the perovskite film through grain boundaries and inside the lattice via iodine vacancies. [7] Under illumination, the superoxide anion (O 2 − ) forms, which is highly reactive and triggers lattice decomposition. [8,9] Nevertheless, proper encapsulation procedures [10,11] can mitigate or, in the best scenario, eliminate the influence of moisture or oxygen on device stability. In addition to that, metal halide perovskites are also sensitive to heat, illumination, and electrical bias, three certain conditions in photovoltaic operation. In perovskite solar cells (PSCs), the interfaces are a weak link with respect to degradation. Electrochemical reactivity of the perovskite's halides has been reported for both molecular and polymeric hole selective layers (HSLs), and here it is shown that also NiO brings about this decomposition mechanism.Employing NiO as an HSL in p-i-n PSCs with power conversion efficiency (PCE) of 16.8%, noncapacitive hysteresis is found in the dark, which is attributable to the bias-induced degradation of perovskite/NiO interface. The possibility of electrochemically decoupling NiO from the perovskite via the introduction of a buffer layer is explored. Employing a hybrid magnesiumorganic interlayer, the noncapacitive hysteresis is entirely suppressed and the device's electrical stability is improved. At the same time, the PCE is improved up to 18% thanks to reduced interfacial charge recombination, which enables more efficient hole collection resulting in higher V oc and FF.

Progress, highlights and perspectives on NiO in perovskite photovoltaics

“…Defect engineering has been widely applied to improve the performance of NiO based devices, either by tuning the concentration of Ni 3+ or by inducing the formation of additional NiOOH. [124][125][126][127] Increasing the Ni 3+ concentration can improve conductivity and charge transfer, but at the same time, it causes non-negligible parasitic absorption. 125,128 The proper use of NiOOH also appear complex due to the very different energetic levels at the different crystalline surfaces.…”

“…3e). 124 Light soaking might be benecial for improving the perovskite crystallinity 138 or either induce interface degradation to NiI 2 (Fig. 3c) 139 or PbI 2 (Fig.…”

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

“…The detrimental interaction of NiO with perovskite ions has been further highlighted by Di Girolamo et al, who reported the occurrence of noncapacitive hysteresis in the dark for NiO-based p-i-n PSCs. [258] The noncapacitive hysteresis has been proposed to arise from bias-induced reactions (e.g., electrochemical reactions such as iodide oxidation) [259,260] at the interface between the HTL and perovskite. In fact, by introducing a solution-processed MgO interlayer, the hysteresis vanished and the devices became electrically more stable.…”

Diffusive and Drift Halide Perovskite Memristive Barristors as Nociceptive and Synaptic Emulators for Neuromorphic Computing

“…In HPs, these filaments are most likely formed by halogen vacancies. [ 32 ] Electrochemical reaction between NiO x and HP upon electrical bias, [ 33 ] and halide oxidation promoted by NiO x [ 34 ] might further increase halogen vacancies in the system and increase the probability of conductive filament formation. Upon sufficient negative bias application, the ions drift to the opposite direction rupturing the conductive filament and subsequently increase the device's resistance (RESET, Figure 1c).…”