The effect of rubidium and guanidinium additives on the morphological, optoelectronic and photovoltaic properties of the state-of-the-art triple A-cation based PSCs is investigated.
Interfacial engineering between the perovskite and hole transport layers has emerged as an effective way to improve perovskite solar cell (PSC) performance. A variety of organic halide salts are developed to passivate the traps and enhance the charge carrier transport. Here, the use of guanidinium iodide (GuaI) for interfacial modification of mixed‐cation (Cs)x(FA)1−xPbI3 perovskite films, which results in the formation of a low‐dimensional δ‐FAPbI3‐like phase on the 3D perovskite surface, is reported. The presence of this thin layer facilitates charge transfer at interfaces and reduces charge carrier recombination pathways as evidenced by enhanced carrier lifetimes and favorable interfacial band alignment. As a result, the power conversion efficiency of the control device is boosted from 19.22% to 20.07%, mainly due to improved open‐circuit voltage (Voc) and fill factor. Furthermore, the post‐treatment with GuaI improves the moisture stability of perovskite polycrystalline films and ambient stability of PSCs.
The quality of perovskite films plays a crucial role in improving the optoelectronic properties and performance of perovskite solar cells (PSCs). Herein, high‐quality CsxFA1−xPbI3 perovskite films with different compositions (x = 0, 5, 10, and 15) are achieved by controlling the amount of cesium chloride (CsCl) in the respective FAPbI3 precursor solution. The effects of CsCl addition on the morphological and optoelectronic properties of the resulting perovskite films and on the performance of the corresponding devices are systematically studied. Introduction of CsCl into FAPbI3 shows a great potential to stabilize the α‐FAPbI3 perovskite phase by forming CsxFA1−xPbI3 films with improved morphology and carrier lifetimes. With an optimal 10 mol% CsCl additive, the average power conversion efficiency (PCE) is increased from 16.83 ± 0.30% for the reference FAPbI3‐based PSCs to 18.87 ± 0.25% (with a steady‐state PCE of 18.89%). Moreover, the optimized device performance is more stable after 20 days than the controlled one under ≈40% humidity in air.
Methylammonium lead bromide (MAPbBr3), which
belongs
to the larger material family of lead halide perovskites (LHPs), has
emerged as a promising semiconductor for the fabrication of single-crystal
(SC)-based photodetectors (PDs). However, there is still a lack of
sufficient understanding of the effect of irradiation power and applied
temperature on the photodetection performance of SC-based perovskite
PDs. Here, we investigate the impact of different light intensities
and temperatures on the photodetection properties of planar-type MAPbBr3 SC-based PD with the help of transient photoresponse and
impedance spectroscopy. The light intensity-dependent study revealed
that the key performance parameters of PD decrease with increasing
irradiation intensity due to changes in charge recombination and carrier
lifetime. On the other hand, the detrimental effect of increasing
temperature on the performance of PD was found to be related to the
ion accumulation, increasing scattering of impurities and phonons,
and change in conductivity and band gap rather than the change in
charge recombination. This study provides a thorough understanding
of the origin of light intensity and temperature-dependent photodetection
properties of SC-based PD, which is crucial for the further advancement
of optoelectronic devices based on LHPs.
Perovskite
solar cells (PSCs) have experienced outstanding advances in power
conversion efficiencies (PCEs) by employing new electron transport
layers (ETLs), interface engineering, optimizing perovskite morphology,
and improving charge collection efficiency. In this work, we study
the role of a new ultrathin interface layer of titanium nitride (TiN)
conformally deposited on a mesoporous TiO2 (mp-TiO2) scaffold using the atomic layer deposition method. Our characterization
results revealed that the presence of TiN at the ETL/perovskite interface
improves the charge collection as well as reduces the interface recombination.
We find that the morphology (grain size) and optical properties of
the perovskite film deposited on the optimized mp-TiO2/TiN
ETL are improved drastically, leading to devices with a maximum PCE
of 19.38% and a high open-circuit voltage (V
oc) of 1.148 V with negligible hysteresis and improved environmental
(∼40% RH) and thermal (80 °C) stabilities.
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.
Titanium dioxide (TiO2) is an extensively used electron transporting layer (ETL) in n–i–p perovskite solar cells (PSCs). Although, TiO2 ETL experiences the high surface defect together with low electron extraction ability, which causes severe energy loss and poor stability in the PSC. In this study, a new intermediate layer consisting of gold nanoparticles functionalized with fully conjugated fullerene C60 derivative (C60‐BCT@Au NPs) that enhances the interfacial contact at ETL/perovskite interface leading to a perovskite film with improved crystallinity and morphology is reported. Moreover, the studies demonstrate that the interface modification of the TiO2 ETL with C60‐BCT@Au NPs substantially improves the charge extraction efficiency from the perovskite layer and suppresses charge recombination processes. Consequently, the resulting device yields a champion efficiency of 19.08% as well as devaluation in hysteresis. In addition, the unencapsulated PSCs with c‐TiO2/C60‐BCT@Au NPs ETL retain 83% and 90% of their original PCEs after 500 h storage in air and exposure to continuous UV illumination for 200 h, respectively. This study provides an effective method to address the electron transporting issues between perovskite and c‐TiO2 ETL for developing stable and efficient PSCs.
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