Thiocyanate-Passivated Diaminonaphthalene-Incorporated Dion–Jacobson Perovskite for Highly Efficient and Stable Solar Cells

Abstract

Two-dimensional (2D) metal halide perovskites have recently emerged as promising photovoltaic materials due to their superior ambient stability and rich structural diversity. However, power conversion efficiencies (PCEs) of the 2D perovskites solar cells (PSCs) still lag behind their three-dimensional (3D) counterpart, particularly due to the anisotropy in the charge carrier mobility and inhomogeneous energy landscape. A promising alternative is Dion−Jacobson (D−J) phase quasi-2D perovskite, where the bulky organic diammonium cations are introduced into inorganic frameworks to remove the weak van der Waals interactions between interlayers and to improve the open-circuit voltage (V oc ). Although the D−J phase 2D perovskite shows a homogeneous energy landscape and better charge transport, their poor crystallinity and existence of higher trap states remain a major challenge for the development of high-efficiency solar cells device. To address this issue, here, we report the eclipsed D−J phase 2D perovskite using 1,5-diaminonaphthalene cation and subsequently treated the film with ammonium thiocyanate (NH 4 SCN) additive to further improve the film crystallinity, out-of-plane orientation, and carrier mobility. We observe that 2 mol NH 4 SCN surface treatment in NDA-based D−J phase perovskite leads to better film morphology and improved crystallinity, as confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Time-resolved photoluminescence (TRPL) spectroscopy and steady-state space charge limited current (SCLC) mobility measurement reveal a significant reduction of trap-assisted nonradiative recombination and improvement of carrier mobility in the thiocyanate-passivated perovskite. Consequently, the PCE of the NH 4 SCN-treated (NDA)(MA) 3 (Pb) 4 (I) 13 perovskite device enhanced nearly 46% from 10.3 to 15.08%. We have further studied intensity-dependent J−V characteristics, which demonstrate the reduction of ideality factor, confirming the effective suppression of trap-assisted nonradiative recombination, consistent with the transient PL results. Electrochemical impedance spectroscopy (EIS) confirms the improved charge carrier transport in NH 4 SCN additive-treated devices. Interestingly, our additive-engineered unsealed perovskite devices retained 75% of their initial efficiency after 1000 h of continuous storage under 60% relative humidity. This study opens up the strategy for developing high-efficiency and stable 2D perovskite solar cells.

Efficient and Highly Stable X-ray Detection and Imaging using 2D (BA)2PbI4 Perovskite Single Crystals

“…The average carrier decay lifetime is 3.02 ns. The narrow FWHM (in PL spectrum) and short average carrier lifetime suggest a strong probability for excitonic carrier recombination and reduced trap-assisted nonradiative recombination. , …”

Ammonium Thiocyanate-Passivated Quasi-Two-Dimensional Dion Jacobson Perovskite Solar Cells for Improved Efficiency and Stability

“…Additive engineering has been proven as an established protocol to improve perovskite film uniformity, crystallinity, compactness, and also to minimize the defect states. , Here, to further improve the photovoltaic efficiency of selected n = 4 phase (XDA)­(MA) 3 (Pb) 4 (I) 13 perovskite active layer, NH 4 SCN passivation was done by adding it directly into the perovskite precursor solution. The detailed scheme for precursor solution of NH 4 SCN additive-assisted (XDA)­(MA) 3 (Pb) 4 (I) 13 perovskite is included in the experimental section . The (XDA)­(MA) 3 (Pb) 4 (I) 13 perovskite with different amounts of NH 4 SCN were fabricated with the molar ratio of XDA/MAI/PbI 2 /HI/NH 4 SCN = 1:3:4:2: x .…”

“…The MASCN additive-assisted PSCs achieved the maximum PCE of 16.25% and maintain superior ambient stability (35 days) in 45% humidity exposure . Recently, our group has shown that 1,5-diamino naphthalene (NDA) organic cation incorporated 2D D-J phase perovskite with NH 4 SCN treatment can lead to PCE of 15% with high moisture stability …”

Highly Efficient and Stable 2D Dion Jacobson/3D Perovskite Heterojunction Solar Cells

“…Almost all of these works have predominately focused on stability enhancement while keeping PCE high by using different organic spacers. Another alternative approach to improve the stability and PCE was pursued by using different surface engineering techniques like cross-linking additives, additive engineering, interface defect engineering, etc. − Among these techniques, additive engineering is one of the most widely employed method which enhances the carrier transport and reduces nonradiative recombination. Various additives such as ammonium chloride (NH 4 Cl), methylammonium chloride (MACl), lead thiocyanate (PbSCN), ammonium thiocyanate (NH 4 SCN), and methylammonium thiocyanate (MASCN) have been utilized for this purpose. − However, a collective effect of incorporating 2D perovskite along with additional passivation engineering on 3D perovskite is almost not explored.…”