Chen Weijie

Nature Energy, Published online: 09 February 2023; doi:10.1038/s41560-023-01205-y

The preparation of 2D/3D perovskite as the optoelectronic material for perovskite solar cells has gradually become an important means to solve the problem of device stability. This review systematically summarizes and discusses the mechanism of 2D/3D structure improving the efficiency and stability of devices from materials to structures to optoelectronic properties.

Perovskite materials have demonstrated excellent performance in the field of solar cells, and the device efficiency has already exceeded 25%. However, to date, perovskite solar cells (PSCs) have not been able to achieve large-scale production. The biggest obstacle to commercializing PSCs is the stability problem that has been widely criticized since their inception. In the last 5 years, the emergence of 2D/3D perovskites has provided a new way to solve this problem. In this review, the representative work on 2D/3D perovskites is summarized, focusing on how 2D/3D structures can simultaneously improve device efficiency and stability. Starting from materials, the current perovskite material system with 2D/3D structure, as well as the bulky organic molecules used to prepare 2D/3D perovskites, is summarized and the corresponding preparation methods are discussed. After that, the influence of the 2D/3D structure on the crystallization of perovskites, the passivation, stabilization, and protection of 2D perovskite on 3D perovskite, and the mechanism of the 2D/3D perovskite heterojunction are discussed in depth. In the end, the development of 2D/3D perovskite from the aspects of research status, advantages, problems encountered, and future research directions is analyzed and prospected.

The mechanical behavior of perovskite films during thermal cycling is investigated and the mechanisms that guide the formation and development of microscopic cracks are revealed. An effective strategy to restrain the generation of cracks in perovskite films is further proposed by constructing a benign compressive strain perovskite film, leading to durable perovskite solar cells.

Abstract

Metal halide perovskites are promising as next-generation photovoltaic materials, but stability issues are still a huge obstacle to their commercialization. Here, the formation and evolution of cracks in perovskite films during thermal cycling, which affect their mechanical stability, are investigated. Compressive strain is employed to suppress cracks and delamination by in situ formed polymers with low elastic modulus during crystal growth. The resultant devices pass the thermal-cycling qualification (IEC61215:2016), retaining 95% of the initial power conversion efficiency (PCE) and compressive strain after 230 cycles. Meanwhile, the p–i–n devices deliver PCEs of 23.91% (0.0805 cm²) and 23.27% (1 cm²). The findings shed light on strain engineering with respect to their evolution, which enables mechanically stable perovskite solar cells.

Publication date: May 2023

Source: Nano Energy, Volume 109

Author(s): Luigi Angelo Castriotta, Emanuele Calabrò, Francesco Di Giacomo, Sathy Harshavardhan Reddy, Daimiota Takhellambam, Barbara Paci, Amanda Generosi, Luca Serenelli, Francesca Menchini, Luca Martini, Mario Tucci, Aldo Di Carlo

A bifunctional cellulose derivative, 6-O-[4-(9H-carbazol-9-yl)butyl]-2,3-di-O-methyl cellulose (C-Cz), with decent carrier transportation and superior passivation effect is developed. When utilized as the interfacial modifier in perovskite solar cells, a remarkably enhanced efficiency of 23.02% is achieved along with significantly improved long-term stability.

Abstract

Interfacial engineering is a vital strategy to enable high-performance perovskite solar cells (PSCs). To develop efficient, low-cost, and green biomass interfacial materials, here, a bifunctional cellulose derivative is presented, 6-O-[4-(9H-carbazol-9-yl)butyl]-2,3-di-O-methyl cellulose (C-Cz), with numerous methoxy groups on the backbone and redox-active carbazole units as side chains. The bifunctional C-Cz shows excellent energy level alignment, good thermal stability and strong interactions with the perovskite surface, all of which are critical for not only carrier transportation but also potential defects passivation. Consequently, with C-Cz as the interfacial modifier, the PSCs achieve a remarkably enhanced power conversion efficiency (PCE) of 23.02%, along with significantly enhanced long-term stability. These results underscore the advantages of bifunctional cellulose materials as interfacial layers with effective charge transport properties and strong passivation capability for efficient and stable PSCs.

Publication date: 15 February 2023

Source: Joule, Volume 7, Issue 2

Author(s): Cheng Sun, Jin-Woo Lee, Changyeon Lee, Dongchan Lee, Shinuk Cho, Soon-Ki Kwon, Bumjoon J. Kim, Yun-Hi Kim

Publication date: May 2023

Source: Journal of Energy Chemistry, Volume 80

Author(s): Dongmei He, Ru Li, Baibai Liu, Qian Zhou, Hua Yang, Xuemeng Yu, Shaokuan Gong, Xihan Chen, Baomin Xu, Shangfeng Yang, Jiangzhao Chen

Publication date: May 2023

Source: Nano Energy, Volume 109

Author(s): Zhenyu Wang, Jintao Wang, Ze Li, Ziqiang Chen, Lianchao Shangguan, Siyu Fan, Yu Duan

Publication date: May 2023

Source: Nano Energy, Volume 109

Author(s): Zijun Yi, Bo Xiao, Xin Li, Yubo Luo, Qinghui Jiang, Junyou Yang

Herein, a hybrid electrode based on Ti₃C₂ MXene nanosheet and Ag nanowires (AgNWs) using reverse sequential process exhibits highly enhanced conductivity and transmittance (13.08 ohm sq⁻¹, 79% @ 550 nm) compared with MXene-alone electrode (113.6 ohm sq⁻¹, 59%). Flexible organic photovoltaic devices using MXene/AgNW/colorless polyimide (cPI) hybrid electrode show improved efficiency of 10.3% than 6.70% of the corresponding MXene/cPI electrode.

To realize flexible and wearable electronic devices in the future, it is important to develop flexible transparent electrodes while replacing indium tin oxide-based transparent electrodes. Herein, a highly conductive transparent electrode based on hybrid materials of MXene nanosheet films and Ag nanowires (AgNWs) is reported, which synergistically combines the advantageous properties of each material. MXene/AgNW/colorless polyimide (cPI) hybrid electrode is prepared utilizing reverse sequential processing of MXene nanosheets and AgNWs and exhibits significantly improved conductivity and transmittance compared with the MXene/cPI electrode. Furthermore, owing to the abundant hydrophilic termination groups (-O and -OH) on the MXene surface, the MXene/AgNW/cPI hybrid electrode shows hydrophilic surface properties and a highly uniform film. Therefore, the MXene/AgNW/cPI hybrid electrode exhibits higher transmittance at 550 nm to 79% than MXene/cPI electrode (59%) and considerably lower sheet resistance (13.08 ohm sq⁻¹) than MXene/cPI electrode (113.6 ohm sq⁻¹). Flexible organic photovoltaic devices fabricated with MXene/AgNW/cPI hybrid electrode achieve higher power conversion efficiency of 10.3% compared with 6.70% of the corresponding MXene/cPI electrode. These results provide the great potential of Ti₃C₂-based MXene hybrid electrode as a flexible transparent electrode, paving the way for various and wider range of applications include solar cells and light-emitting diodes.

High-efficiency perovskite light-emitting diode (PeLED) with an optimized external quantum efficiency of 21.3% is achieved through delicate engineering of monovalent cations. The inorganic cation Cs⁺ in the perovskite leads to suppressed cation accumulation and mitigated electrochemical reactions in different functional layers. The device exhibits a long half-lifetime T ₅₀ of 190.1 h, representing the most stable PeLEDs based on 3D perovskite layer.

Abstract

The delicate engineering of monovalent cations in perovskite material has led to continuous performance breakthroughs and stability improvement for the perovskite light-emitting diodes (PeLEDs). However, the exact role of A-site cations on the electroluminescence (EL) performance and degradation mechanism of PeLEDs has not been systematically answered yet. Herein, it is demonstrated that the most commonly used methylammonium cation (MA⁺) has an adverse effect on the electrochemical reaction at the interface between perovskite and metal-oxide layer, leading to deteriorated EL performance as compared to that of the formamidinium cation (FA⁺)-based perovskite. It reveals that the accelerated deprotonation process of MA⁺ under an electric field will aggravate the reaction between iodide and metal ion in oxide layer. The further substitution of a small portion of FA⁺ with inorganic cesium cation (Cs⁺) results in much enhanced crystallinity and enlarged crystal size, leading to an optimized peak external quantum efficiency of 21.3%. The ion migration process in the PeLEDs can be significantly suppressed with Cs⁺ incorporation, leading to a smaller roll-off under large current density and an elongated half-lifetime of 190.1 h under a current density of 20 mA cm^-2, representing one of the most stable PeLEDs based on 3D perovskite layer.

A pressure-driven self-trapping exciton transformation from dark to bright state was achieved in low-dimensional halide perovskites, revealing the physicochemical mechanism of pressure-induced emission.

Abstract

Pressure-induced emission (PIE) associated with self-trapping excitons (STEs) in low-dimensional halide perovskites has attracted great attention for better materials-by-design. Here, using 2D layered double perovskite (C₆H₅CH₂CH₂NH₃ ⁺)₄AgBiBr₈ as a model system, we advance a fundamental physicochemical mechanism of the PIE from the perspective of carrier dynamics and excited-state behaviors of local lattice distortion. We observed a pressure-driven STE transformation from dark to bright states, corresponding a strong broadband Stokes-shifted emission. Further theoretical analysis demonstrated that the suppressed lattice distortion and enhanced electronic dimensionality in the excited-state play an important role in the formation of stabilized bright STEs, which could manipulate the self-trapping energy and lattice deformation energy to form an energy barrier between the potential energy curves of ground- and excited-state, and enhance the electron-hole orbital overlap, respectively.

Publication date: 10 March 2023

Source: Electrochimica Acta, Volume 444

Author(s): Min Shi, Tiancheng Bai, Shushu Du, Huimin Sha, Hao Chen, Xiaohu Ma, Yudong Xu, Yiqing Chen

Herein, a model for calculating the loss distribution for different operating conditions is presented. A perovskite/silicon tandem module is used as a case study. Simulations show that the thermalization, reflection, and inverter losses increase by 1.2%, 1.1%, and 1.4%, when operating outdoors compared to standard test conditions. Additionally, it shows that fill factor gains compensation for current mismatches.

The tandem PV technology can potentially increase the efficiency of PV modules over 30%. To design efficient modules, a quantification of the different losses is important. Herein, a model for quantifying the energy loss mechanisms in PV systems under real-world operating conditions with a level of detail back to the components and their fundamental properties is presented. Totally, 17 losses are defined and divided into four categories (fundamental, optical, electrical, and system losses). As example, a system based on a > 29% two-terminal perovskite/silicon tandem cell is considered. The loss distribution at standard test conditions is compared to four geographical locations. The results show that the thermalization, reflection, and inverter losses increase by 1.2%, 1.1%, and 1.4%, respectively, when operating outdoors. Additionally, it is quantified how fill factor gains partly compensate the current mismatch losses. For example, a mismatch of 7.0% in photocurrent leads to a power mismatch of 1.2%. Therefore, the power mismatch should be used as indicator for mismatch losses instead of a current mismatch. Finally, herein, it is shown that solar tracking increases not only the in-plane irradiance but also the efficiency of the tandem module.

In this study, a synergistic strategy is reported via initiatively inducing vertical graded PbI₂ distribution in the whole perovskite film and capping cis-Ru(H₂dcbpy)(dnbpy)(NCS)₂ (Z907) internal encapsulation layer on the surface of perovskite. The resultant perovskite solar cells employing 1.60 eV perovskite absorber achieves a superior power conversion efficiency of 24.28% with outstanding open circuit voltage (V _OC) (1.253 V) and fill factor (81.25%).

Abstract

Introducing excess PbI₂ has proven to be an effective in situ passivation strategy for enhancing efficiency of perovskite solar cells (PSCs). Nevertheless, the photoinstability and hysteresis are still tough issues owing to the photolysis nature of PbI₂. Moreover, the humidity-related degradation of perovskite films is also a difficult territory to cover in such an in situ passivation strategy. Herein, a synergistic strategy is reported via initiatively inducing vertical graded PbI₂ distribution (GPD) in the whole perovskite film and capping a cis-Ru(H₂dcbpy)(dnbpy)(NCS)₂ (Z907) internal encapsulation (IE) layer on the surface to ameliorate the above issues. The GPD design can enhance luminescence, prolong carrier lifetimes, ascertaining the improvement of efficiency and elimination of photoinstability in the PSCs. Besides, the introduced IE layer not only can promote the moisture and thermal resistance, but also inhibit Pb leakage and ion migration in the PSCs. Through the synergetic regulations, the resultant PSCs exhibit an impressive open circuit voltage (V _OC) of 1.253 V, fill factor of 81.25%, and power conversion efficiency (PCE) of 24.28%. Moreover, the PSCs maintain 91% of its initial PCE at relative humidity of 85% after 500 h aging and 94% under continuous heating at 85 °C after 750 h aging.

Publication date: April 2023

Source: Nano Energy, Volume 108

Author(s): Yue Ma, Qizhen Song, Xiaoyan Yang, Huachao Zai, Guizhou Yuan, Wentao Zhou, Yihua Chen, Fengtao Pei, Jiaqian Kang, Hao Wang, Tinglu Song, Xueyun Wang, Huanping Zhou, Yujing Li, Yang Bai, Qi Chen

A reactive surface modification strategy exploiting the pyrolysis of urea is developed to deal with the nickel oxide hole selective contact. The surface reactions reduce high-valence nickel states and hydroxyl groups on the NiO _x surface, enabling a high-quality NiO _x /perovskite heterointerface. The NiO _x -based perovskite solar cells achieve an impressive efficiency of 23.61% and a fill factor of over 86%.

Abstract

The poor interface quality between nickel oxide (NiO _x ) and halide perovskites limits the performance and stability of NiO _x -based perovskite solar cells (PSCs). Here a reactive surface modification approach based on the in situ decomposition of urea on the NiO _x surface is reported. The pyrolysis of urea can reduce the high-valence state of nickel and replace the adsorbed hydroxyl group with isocyanate. Combining theoretical and experimental analyses, the treated NiO _x films present suppressed surface states and improved transport energy level alignment with the halide perovskite absorber. With this strategy, NiO _x -based PSCs achieve a champion power conversion efficiency (PCE) of 23.61% and a fill factor of over 86%. The device's efficiency remains above 90% after 2000 h of thermal aging at 85 °C. Furthermore, perovskite solar modules achieve PCE values of 18.97% and 17.18% for areas of 16 and 196 cm², respectively.

A series of terpolymers are developed by introducing the BN bond into the polymer chain of PM6, which lowers the HOMO level, reduces the ΔE _ST, and optimizes the morphology of the active blend, contributing to a high PCE of 19.02% with reduced E _loss and charge recombination.

Abstract

Suppressing the photon energy loss (E _loss), especially the non-radiative loss, is of importance to further improve the device performance of organic solar cells (OSCs). However, typical π-conjugated semiconductors possess a large singlet–triplet energy gap (ΔE _ST), leading to a lower triplet state than charge transfer state and contributing to a non-radiative loss channel of the photocurrent by the triplet state. Herein, a series of triplet polymer donors are developed by introducing a BNIDT block into the PM6 polymer backbone. The high electron affinity of BNIDT and the opposite resonance effect of the BN bond in BNIDT results in a lowered highest occupied molecular orbital (HOMO) and a largely reduced ΔE _ST. Moreover, the morphology of the active blends is also optimized by fine-tuning the BNIDT content. Therefore, non-radiative recombination via the terminal triplet loss channels and morphology traps is effectively suppressed. The PNB-3 (with 3% BNIDT):L8-BO device exhibits both small ΔE _ST and optimized morphology, favoring more efficient charge transfer and transport. Finally, the simultaneously enhanced V _oc of 0.907 V, J _sc of 26.59 mA cm⁻², and FF of 78.86% contribute to a champion PCE of 19.02%. Therefore, introducing BN bonds into benchmark polymers is a possible avenue toward higher-performance of OSCs.