Photostability Of Perovskite Solar Cells Research Articles

Waste-derived carbon quantum dots for improving the photostability of perovskite solar cells to > 1,000 h

Power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached 26.1%, but PSC devices are plagued by poor stability when exposed to light (especially ultraviolet (UV) radiation), heat, and moisture. UV stability remains a significant challenge to overcome. Luminescent down-shifting (LDS) filters have shown significant enhancement in photostability and efficiency for PSCs. However, most explored LDS materials are costly, non-biodegradable, and the resulting photostability is limited to ∼100 h. In this report, as-obtained waste filtrate from the polyaniline (PANI) synthesis is used to synthesize fluorescent PANI carbon quantum dots (PANI-CQDs) using a facile hydrothermal method. Here we report, for the first time, the use of waste-derived PANI-CQDs to fabricate UV filters that are low-cost, bio-degradable, and room-temperature processible and, importantly, impart high UV and photostability to the PSCs. PSCs with these filters retained 90% and 100% of their initial performance when exposed to UV light and AM 1.5 solar radiation, respectively, for more than 900 h, while PSCs without filters degraded to 14 and 70% of their initial performance under the same conditions. Hence, we clearly show that using a waste-derived LDS filter improves the UV stability of PSCs by six times and photostability beyond 1,000 h.

Enhanced Thermal and Photostability of Perovskite Solar Cells by a Multifunctional Eu (III) Trifluoromethanesulfonate Additive

AbstractPerovskite solar cells (PSCs) have witnessed a meteoric rise in device performance. However, maintaining photostability, particularly under thermal stress, remains a challenge due to defect formation in the perovskite layer. This study introduces europium (III) trifluoromethanesulfonate [Eu(OTF)3] as a multifunctional additive in two‐step processed perovskite films, significantly improving the performance and high‐temperature photostability of n‐i‐p PSCs. Density function theory (DFT) calculations reveal that the OTF− anion strongly coordinates with Pb2+, effectively inhibiting iodine vacancy defect formation. The addition of Eu(OTF)3 promotes perovskite grain growth to ≈2 µm and enhances film crystallinity. PSCs with a structure of ITO/SnO2/perovskite/PDCBT/NiOx/Au achieve a champion power conversion efficiency (PCE) of 23.8%. Under 85 ± 5 °C and 1 sun illumination at an open circuit in ambient air, the PSCs with Eu(OTF)3 retain 82% of their initial PCE after aging for 1500 h.

Near field control for enhanced photovoltaic performance and photostability in perovskite solar cells

We present a strategy for photon management in front contact of perovskite solar cells (PSCs) compatible with tandem and flexible PSCs capable of optimizing device characteristics while providing an additional mechanism to overcome excessive focusing that affects the device’s photostability. Rigorous validation of the numerical modeling used was performed by fabricating PSCs in a superstrate configuration optimized to reach high performance, ECE = 17.4%, V OC = 1.02 V, J SC = 22.3 mA/cm 2 , and FF = 77%. These 3D electromagnetic simulations combining the finite-difference time-domain (FDTD) and finite element method (FEM) techniques provide detailed insights of the photonic and electrical effects in PSCs. Numerical optimization of the dual capabilities of a novel nanostructured front contact enables control of the absorbed power density distribution to maximize efficiency while simultaneously minimizing nanostructure-related sub-wavelength focusing effects. In-depth analysis of the proposed photon management reveals enhanced electrical characteristics to maximize charge extraction leading to J SC enhancements of ~15 that can be as high as 33% for ultra-thin active layers suitable for flexible PSCs compared to planar PSCs performance. Furthermore, we show that the design of the front contact layer’s nanostructure enables control of the power density distribution in the device to engineer PSCs' photostability without compromising performance enhancements afforded by the nanophotonic front contact. Details of the nanophotonic front contact, device, and fabrication process are provided. • The front contact integrated with hybrid nanoholes is designed for efficient perovskite solar cells (PSCs). • Demonstrates the ability to modulate the illumination for high efficiency and better photostability of PSCs. • Optoelectronic device modeling and performance, including photonic response, were investigated by 3D Multiphysics approach. • Validation of the Multiphysics approach against high-quality PSC’s detailed experimental data is conducted. • The proposed nanophotonic device allows enhancing J SC and ECE by 15~33% and 30%, respectively, compared to the reference device.

Influence of grain size on the photo-stability of perovskite solar cells

Organometallic perovskite solar cells have recently attracted huge attention as one of the most promising photovoltaic technologies. Despite higher efficiency achieved in recent years, the instability of perovskite solar cells remains as the biggest problem to be solved. Recently, researchers have developed several encapsulation techniques to enhance the device stability against moisture, but the stability of the device under light soaking did not receive that much attention. Previously, we had studied the device physics behind photo-induced degradation of the perovskite solar cells, and we found that the performance degradation during light exposure is attributed to the generation and migration of mobile ions. In this paper, we investigated the effect of the grain size on the photo-stability and mobile ion generation in perovskite solar cells. We found that with larger perovskite film grain size, the ion generation rate decreased significantly under light exposure, which leads to less performance degradation. This result was further confirmed by our ion density measurement using transient ionic current.

A UV-stable Perovskite Solar Cell Based on Mo-doped TiO2 Interlayer

Mo-doped TiO2 interlayer increases the UV photostability of perovskite solar cells through the redox shuttle between Mo(VI) and Mo(V), which is actually a kind of Mo redox microbattery. These micro...

Photo-stability of perovskite solar cells with Cu electrode

Towards higher stability of perovskite solar cells, Cu has been observed to be more suitable electrode material compared to conventional Al and Ag electrodes. The photo-stability of such devices has not been explored much in the literature, therefore we present here the investigation carried out towards the photo-stability of PSCs based on top Cu electrodes. The PSCs were prepared in normal geometry and stored in dark, under continuous illumination of a white LED lamp inside the laboratory and under direct sunlight outside the laboratory and tested as per the international summit on organic photovoltaics stability protocols. In dark storage the encapsulated solar cells exhibited highest stability but under illumination they exhibited degradation in their performance and the degradation was fastest in the direct sunlight. Degradation under illumination has been attributed to the photo-oxidation of the perovskite film. Cu has been observed to diffuse into and react with the underlying perovskite film and the ultraviolet and infrared contents in direct sunlight accelerated the photo-oxidation and chemical reactions between Cu and perovskite film. The chemical reactions of Cu electrode with perovskite constituents made it disappear after some time. These investigations suggest that Cu too is not a very stable electrode material for PSCs under natural operating conditions.

Enhancing Photostability of Perovskite Solar Cells by Eu(TTA)2(Phen)MAA Interfacial Modification.

Organic-inorganic lead halide perovskite solar cells (PSCs) exhibit spectacular changes in the photovoltaic area, but they still face the challenges of full spectral utilization and photostability under continuous light irradiation. The ultraviolet (UV) part in sunlight could induce oxygen vacancy in the mesoporous TiO2 (m-TiO2) layer, resulting in the degradation of perovskite photoactive films and the rapidly decreased device performance. In this work, we demonstrate that an effective luminescent downconversion material, Eu(TTA)2(Phen)MAA (ETPM), can be used as an interfacial modifier between the m-TiO2 layer and the perovskite photoactive layer to improve the power conversion efficiency (PCE) from 17.00 to 19.07%. The improved device performance can be ascribed to the effective utilization of incident UV light and reduced carrier recombination. Meanwhile, the conversion of the UV light by ETPM could inhibit the stability loss of the device under irradiation. As a result, the modified PSCs can maintain 86% of their initial value under continuous light soaking for 100 h, higher than that of 40% for the control device. This work indicates that the introduction of the luminescent downconversion material ETPM can successfully improve the PCE and photostability of PSCs.

Intrinsic Behavior of CH3NH3PbBr3 Single Crystals under Light Illumination

AbstractSingle crystal CH3NH3PbBr3 samples are exposed to light illumination, with a light intensity about seven times stronger than the sun while under ultrahigh vacuum (UHV) conditions, in order to investigate their chemical and structural stability from prolonged light illumination. X‐ray photoemission spectroscopy measurements show that within 10 h of illumination, about half of the initial C, N, and Br elemental concentrations leave the surface and about half of the perovskite's Pb is converted into metallic Pb. Light exposures while in the UHV system also significantly roughen the surface, and surprisingly, empty voids form ≈1 to 3 µm down in the light exposed region. A framework based on the Kirkendall effect is put forward to explain the observed void formation. This proposed model may be relevant to the slow degradation of perovskite solar cells, which is sometimes attributed to irreversible chemical reactions from undesired diffusion. These measurements and observations reveal the intrinsic behavior of the CH3NH3PbBr3 single crystals under light illumination while in a UHV system where volatile species are free to leave, in contrast to existing device studies on the photostability of perovskite solar cells.

Photostability of Perovskite Solar Cells: Unraveling Photostability of Mixed Cation Perovskite Films in Extreme Environment (Advanced Optical Materials 20/2018)

Photostability of Perovskite Solar Cells: Unraveling Photostability of Mixed Cation Perovskite Films in Extreme Environment (Advanced Optical Materials 20/2018)

Discrete Iron(III) Oxide Nanoislands for Efficient and Photostable Perovskite Solar Cells

Perovskite solar cells typically use TiO2 as charge extracting materials, which reduce the photostability of perovskite solar cells under illumination (including ultraviolet light). Simultaneously realizing the high efficiency and photostability, it is demonstrated that the rationally designed iron(III) oxide nanoisland electrodes consisting of discrete nanoislands in situ growth on the compact underlayer can be used as compatible and excellent electron extraction materials for perovskite solar cells. The uniquely designed iron(III) oxide electron extraction layer satisfies the good light transmittance and sufficient electron extraction ability, resulting in a promising power conversion efficiency of 18.2%. Most importantly, perovskite solar cells fabricated with iron(III) oxide show a significantly improved UV light and long‐term operation stabilities compared with the widely used TiO2‐based electron extraction material, owing to the low photocatalytic activity of iron(III) oxide. This study highlights the potential of incorporating new charge extraction materials in achieving photostable and high efficiency perovskite photovoltaic devices.

Spray deposited lanthanum doped TiO2 compact layers as electron selective contact for perovskite solar cells

TiO2 compact layers are wildly used for electron selective contact in perovskite solar cells. The function of TiO2 selective contact can be modified by doping metal ions in the TiO2 compact layers. As lanthanide elements usually exhibit unique properties for their incompletely occupied 5d or 4f orbitals, we prepared lanthanum doped TiO2 compact layers by spray pyrolysis method as the electron selective contact of perovskite solar cells. SEM images indicate lanthanum dopants improve the smoothness of TiO2 layers. In the optimized concentration, the average PCE of devices is promoted from 12.4% to 14.4% with the highest PCE of 17.2%, which comes from the improvement on charge transfer and recombination. Moreover, the Lanthanum dopants also lead to the improvement in photo-stability of perovskite solar cells. For the device with optimized La concentration, 80% of its original PCE is preserved after 200h aging under continuous one sun illumination.

Enhanced Performance and Photostability of Perovskite Solar Cells by Introduction of Fluorescent Carbon Dots.

Perovskite solar cells (PSCs) with high efficiency have recently received tremendous attention, but the stability under light irradiation, namely, photostability, of PSCs still represents a major obstacle that must be overcome before their practical applications can be used. The degeneration of perovskite under ultraviolet irradiation from sunlight is a major impacting factor. To solve this problem, in this work we introduce fluorescent carbon dots (CDs), which could effectively convert ultraviolet to blue light in the mesoporous TiO2 (m-TiO2) layer of the traditional PSCs. As a result, CD-based devices exhibit an improved power conversion efficiency (PCE) of 16.4% on average compared to 14.6% for bare devices, and the light stability of CD-based devices is highly enhanced. These devices can maintain nearly 70% of the initial efficiency after 12 h of full sunlight illumination, while the bare devices maintain only 20% of the initial efficiency. This work indicates that fluorescent down conversion based on CDs is a novel and effective approach to improve the performance and photostability of PSCs.