Chen Weijie

Publication date: October 2022

Source: Journal of Energy Chemistry, Volume 73

Author(s): Yanyu Deng, Guanhua Ren, Danao Han, Wenbin Han, Zhuowei Li, Chunyu Liu, Wenbin Guo

In this study, the quality of large-area perovskite film is improved by using ionic liquid additives via forming a new Pb-N bonding between the ionic liquid and Pb²⁺. A champion power conversion efficiency of 24.4% for small-area (0.148 cm²) devices and 20.4% for larger-area modules (10.0 cm²) are achieved. The devices and modules exhibit excellent long-term stability.

Abstract

Metal-halide perovskite solar cells (PSCs) exhibit outstanding power conversion efficiencies (PCEs) when fabricated as mm-sized devices, but creation of high-performing large-area modules that are stable on a sufficiently long timescale still presents a significant challenge. Herein, the quality of large-area perovskite film is improved by using ionic liquid additives via forming a new Pb-N bonding between the ionic liquid and Pb²⁺. This new bond can be modulated by a critical screening of the anion structure of the ionic liquid. The selected ionic liquid effectively reduces the defects of the perovskite films and markedly elongate their carrier lifetimes. As a result, a champion PCE of 24.4% for small-area (0.148 cm²) devices and 20.4% for larger-area (10.0 cm²) modules under AM 1.5G irradiation is achieved. More importantly, the modified devices retain 90% of their peak PCE after aging for 1900 h at 65 ± 5 °C (ISOS-T-1) and 80% after continuous light soaking for 750 h. The non-encapsulated modules maintained 80% of their peak PCE after 1100 h of aging in the air with a relative humidity of 35 ± 5% and temperature of 25 ± 5 °C under dark (ISOS-D-1), showing great potential for future commercialization.

The wide-bandgap perovskite (WBG) of Cs_0.2FA_0.8Pb(I_0.6Br_0.4)₃ (FA: HC(NH₂)₂) is employed for semitransparent perovskite solar cells (ST-PSCs). By simultaneous interfacial modification and defect passivation to suppress energy loss and nonradiative recombination, a high efficiency of 15.06% is achieved for WBG-PSCs with excellent stability. Consequently, the ST-PSCs realize 14.4% of efficiency with high average visible transmittance of 38% through optimizing the semitransparent electrode.

Abstract

Perovskite materials offer a great potential in the application of semitransparent solar cells, owing to the tunable bandgap, ease of preparation and excellent photovoltaic property. A majority of works exhibit high average visible-light transmittance (AVT) for semitransparent perovskite solar cells (ST-PSCs) through decreasing perovskite thickness, leading to sacrificing the power conversion efficiency (PCE) of the device. Herein, a wide-bandgap (WBG) perovskite of Cs_0.2FA_0.8Pb(I_0.6Br_0.4)₃ is applied as absorber in ST-PSCs, which is a tremendous progress to balance both large PCE and high AVT. Moreover, a strategy of simultaneous interfacial modification and defect passivation is provided to enhance the performance of WBG ST-PSCs. Consequently, an inverted planar structure WBG perovskite solar cell (PSC) achieves 15.06% of PCE with excellent stability by restraining the interfacial energy loss and suppressing the nonradiative recombination. Furthermore, the ST-PSC obtains high PCE of 14.40% with an AVT of 38% by means of optimizing the transparent electrode. This work provides an efficient and simple method to improve the performance and AVT of ST-PSCs for the application in building-integrated photovoltaics.

Efficient red perovskite light-emitting diodes (PeLEDs) with high luminance and low efficiency roll-off are fabricated by manipulating the crystallization kinetics of PEABr-CsPbI₃. The nonradiative losses are greatly reduced in the passivation-free perovskite films with excess PbI₂ and anti-solvent treatment. The optimized PeLEDs achieve a peak external quantum efficiency of 19.6%, which keeping at 17.2% under the luminance of 1000 cd m^–2.

Abstract

CsPbI₃ is attractive for efficient and cost-effective red perovskite light-emitting diodes (PeLEDs), but its black phases still suffer from the metastable structure. The incorporation of large-size organic cations has been widely used to construct quasi-2D perovskites to stabilize the black phases. However, the multiple-phase quasi-2D perovskites usually show abundant interface defects and enhanced Auger recombination, leading to the low luminance and serious efficiency roll-off in PeLEDs. Herein, highly efficient red PeLEDs are demonstrated with high luminance and low efficiency roll-off realized by manipulating the crystallization kinetics of phenethylamine bromide (PEABr) incorporated CsPbI₃. PEABr-CsPbI₃ nanocrystal films with much larger and more oriented β-CsPbI_xBr_3-x grains are successfully obtained through appropriately increasing PbI₂ content and coordinating with anti-solvent treatment. The carrier recombination dynamics investigations reveal that the trap-assisted recombination and Auger recombination are greatly reduced in the passivation-free PEABr-CsPbI₃ films by rational crystallization regulation. A peak external quantum efficiency (EQE) up to 19.6% is achieved in the red PeLEDs with a stable emission peak at 672 nm, which is maintained as high as 17.2% at a high luminance of over 1000 cd m⁻². This study could shed light on modulating the crystallization kinetics of pervoskites to optimize carrier recombination dynamics toward high performance PeLEDs.

In this study, a fluorinated dual-interface design is proposed for low-temperature carbon-based CsPbI₂Br perovskite solar cells by applying potassium trifluoroacetate as cathode interlayer and 4-trifluorophenyl methylammonium bromide as anode passivation layer. As a result, the optimized device achieves the highest efficiency of 14.05% and improved moisture, thermal, and illumination stability in ambient air.

Abstract

Carbon-based inorganic perovskite solar cells (C-PSCs) have attracted intensive attention owing to their low cost and superior thermal stability. However, the bulk defects in perovskites and interfacial energy level mismatch seriously undermine their performance. To overcome these issues, a multifunctional dual-interface engineering is proposed with a focus on low-temperature CsPbI₂Br C-PSCs, where the potassium trifluoroacetate (KTFA) and the 4-trifluorophenyl methylammonium bromide (CF₃PMABr) are introduced beneath and on top of the perovskite layer, respectively. It is found that TFA^- ions locate at the SnO₂/CsPbI₂Br interface, whereas a small amount of K⁺ ions diffuse into perovskite lattice to participate in nucleation and crystallization, resulting in more favored interfacial energy level alignment, improved film quality, passivated interfacial defects, released interfacial strain, as well as suppressed charge recombination and ion migration. Meanwhile, the CF₃PMABr passivates I/Br vacancies and forms 2D perovskite capping layer to facilitate hole extraction at the CsPbI₂Br/carbon interface. As a result, a remarkable power conversion efficiency (PCE) of 14.05% with an open-circuit voltage of 1.273 V is achieved. To the best of the authors’ knowledge, it is currently the highest PCE reported for low-temperature CsPbI₂Br C-PSCs. Furthermore, the nonencapsulated device exhibits improved moisture, thermal, and illumination stability in ambient air.

A device architecture with n-type oxide/perovskite halide/p-type oxide for sputtering damage-free semi-transparent perovskite solar cells (PSCs) is reported. The semi-transparent PSC based on oxide/halide/oxide architecture shows an enhanced power conversion efficiency of 19.5% (20.5% with a back reflector), which is the highest value among reported organic-free semi-transparent PSCs thus far.

Abstract

A device architecture with n-type oxide/perovskite halide/p-type oxide for the sputtering damage-free semi-transparent perovskite solar cells (PSCs) is reported. A p-type nickel oxide (NiO _x ) nanoparticle overlayer on a perovskite layer is introduced to act as both a hole transporting layer and buffer layer to avoid sputtering damage during deposition of transparent conducting oxide. The NiO _x based semi-transparent PSCs exhibit superior durability under harsh sputtering conditions such as high temperature and sputtering power, enabling the high quality of transparent electrodes. With optimal sputtering condition for tin-doped indium oxide (ITO) as a top transparent electrode, the semi-transparent device shows an enhanced power conversion efficiency (PCE) of 19.5% (20.5% with a back reflector), which is higher than that of the opaque device (19.2%). The semi-transparent devices also shows superior storage stability without encapsulation under 10% relative humidity, retaining over 90% of initial PCE for 1000 h. By controlling the molar concentration of perovskite solution, a semi-transparent PSC with a PCE of 12.8%, showing a high average visible transmittance (AVT) of 30.3%, is fabricated. The authors believe that this architecture with n-type oxide/perovskite halide/p-type oxide represents a cornerstone for the high performance and commercialization of semi-transparent PSCs.

Developing efficient and flexible thick-film organic solar cells (OSCs) is crucial for potential industrial printing. An effective strategy combining ternary strategy with functional solid additives is proposed to optimize intra-domain molecular stacking and inter-domain interactions, effectively improve mechanical stability, and reduce thickness sensitivity of the active layer, offering a superior solution for the problems faced by OSC industrial production.

Abstract

Efficient organic solar cells (OSCs) equipped with thick-film active layers and high flexibility are of great significance for industrial preparation and practical applications. Herein, a ternary strategy coupled with a functional additive is employed to obtain efficient thick-film flexible OSCs. A novel polymer donor PBB1-F with good planarity is synthesized as a third component to optimize photon capture and molecular stacking. Meanwhile, a high dielectric constant polyarene ether (PAE) functional additive with strong adhesion not only greatly improves exciton dissociation efficiency, but also acts as locking cage-like for effective enhancement of the mechanical stability of active layer. As a result, the PM6:PBB1-F:Y6-BO-4Cl and PM6:PBB1-F:BTP-eC9 based ternary OSCs with PAE exhibit an efficiency of 17.91% and 18.51% under rigid thin-film state, and perform better under thick-film state of rigid (16.40% and 16.84%) and flexible (14.78% and 14.95%). Under the protection of the polymers, tight entanglement and cage-like PAE adhesion, the elongation at break of the active layer increases by more than fourfold (27.3%), and gives a super flexible thick-film OSCs that maintains more than 90% performance after 1000 bending cycles with a diameter of 10 mm. Overall, this work provides a new feasible scheme to effectively solve thickness sensitivity and flexibility issues in the context organic photovoltaic applications.

A high-performance polythiophene organic solar cell with a power conversion efficiency of 16.4% is demonstrated, which is enabled by sequentially fluorinated thiophene-based polymers with a low-lying highest occupied molecular orbital level, high crystalline properties, and the desired temperature-dependent aggregation behavior. These beneficial features afford an optimal bulk heterojunction morphology with a suitable energy offset and low energetic disorder.

Abstract

Polythiophenes (PTs) have attracted considerable interest for application in organic solar cells (OSCs) owing to their simple molecular structures and low-cost synthesis. However, the power conversion efficiencies (PCEs) of PT-based OSCs are lower than those of state-of-the-art OSCs. Herein, the development of two sequentially fluorinated PT donors (PT-2F and PT-4F) is reported for realizing highly efficient OSCs. PT-2F and PT-4F are designed to contain two and four fluorine atoms, respectively, per repeating unit to decrease their highest occupied molecular orbital energy levels and increase the open-circuit voltages of the OSCs. Importantly, the PT-4F polymers exhibit high backbone rigidity and the desired temperature-dependent aggregation behavior, affording well-developed crystalline structures in thin films for efficient charge transport. These beneficial features promote the construction of an optimal blend morphology of PT-4F:small-molecule acceptor with a suitable energy offset and low energetic disorder. Thus, the PT-4F-based binary and ternary OSCs achieve high PCEs of 15.6% and 16.4%, respectively.

Publication date: October 2022

Source: Nano Energy, Volume 101

Author(s): Yan Zhan, Jingsong Peng, Can Cao, Qunfeng Cheng

Publication date: October 2022

Source: Nano Energy, Volume 101

Author(s): Zaheer Abbas, Seung Un Ryu, Muhammad Haris, Chang Eun Song, Hang Ken Lee, Sang Kyu Lee, Won Suk Shin, Taiho Park, Jong-Cheol Lee

Publication date: 17 August 2022

Source: Joule, Volume 6, Issue 8

Author(s): Xiaobo Zhou, Chao Zhao, Awwad Nasser Alotaibi, Hongbo Wu, Hafiz Bilal Naveed, Baojun Lin, Ke Zhou, Zaifei Ma, Brian A. Collins, Wei Ma

Publication date: 17 August 2022

Source: Joule, Volume 6, Issue 8

Author(s): Xin Liu, Ziping Zhong, Rihong Zhu, Jiangsheng Yu, Gang Li

Nature Energy, Published online: 07 July 2022; doi:10.1038/s41560-022-01059-w

The photovoltaic gap measured by ultraviolet and low-energy photoelectron spectroscopy (UPS/LE-IPES) gives the best correlation to device properties, enabling the prediction of maximum V _oc. Cyclic voltammetry (CV)-derived redox potentials are less meaningful for predicting the energetic landscape at the “donor”–“acceptor” interface.

Abstract

The frontier molecular energy levels of organic semiconductors are decisive for their fundamental function and efficiency in optoelectronics. However, the precise determination of these energy levels and their variation when using different techniques makes it hard to compare and establish design rules. In this work, the energy levels of 33 organic semiconductors via cyclic voltammetry (CV), density functional theory, ultraviolet photoelectron spectroscopy, and low-energy inverse photoelectron spectroscopy are determined. Solar cells are fabricated to obtain key device parameters and relate them to the significant differences in the energy levels and offsets obtained from different methods. In contrast to CV, the photovoltaic gap measured using photoelectron spectroscopy (PES) correlates well with the experimental device V _OC. It is demonstrated that high-performing systems such as PM6:Y6 and WF3F:Y6, which are previously reported to have negligible ionization energy (IE) offsets (ΔIE), possess sizable ΔIE of ≈0.5 eV, determined by PES. Using various D–A blends, it is demonstrated that ΔIE plays a key role in charge generation. In contrast to earlier reports, it is shown that a vanishing ΔIE is detrimental to device performance. Overall, these findings establish a solid base for reliably evaluating material energetics and interpreting property–performance relationships in organic solar cells.

Symmetric and asymmetric near-infrared double-cable conjugated polymers based on a non-fused-ring thieno[3,4-c]pyrrole-4,6-dione (TPD) core with 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) side units were successfully synthesized for application in single-component organic solar cells (SCOSCs). The asymmetric polymer exhibited improved hole mobility, leading to SCOSCs with high quantum efficiencies over 0.80 and power conversion efficiencies over 10 %.

Abstract

Double-cable conjugated polymers with near-infrared (NIR) electron acceptors are synthesized for use in single-component organic solar cells (SCOSCs). Through the development of a judicious synthetic pathway, the highly sensitive nature of the 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC)-based electron acceptors in basic and protonic solvents is overcome. In addition, an asymmetric design motif is adopted to optimize the packing of donor and acceptor segments, enhancing charge separation efficiency. As such, the new double-cable polymers are successfully applied in SCOSCs, providing an efficiency of over 10 % with a broad photo response from 300 to 850 nm and exhibiting excellent thermal/light stability. These results demonstrate the powerful design of NIR-acceptor-based double-cable polymers and will enable SCOSCs to enter a new stage.

The synthetic process of dithienophthalimide (DPI) was simplified with a significant reduction of the synthetic cost by using chromium-mediated cyclization. Furthermore, two DPI-based nonhalogenated wide-band gap copolymers are synthesized. The binary organic solar cells based on pBDTT-DPI-Me : Y6 achieve a power conversion efficiency as high as 16.55 %. These results highlight DPI as an attractive A-unit for the development of new high-performance and low-cost organic semiconductors.

Abstract

Imide-functionalized arenes have been one of the most promising acceptor (A) units in organic solar cells (OSCs). However, dithienophthalimide (DPI), a hybrid of thieno-[3,4-c]pyrrole-4,6-dione (TPD) and bithiophene imide (BTI) units, has not been revisited since its first synthesis, likely owing to the high synthetic cost of the reported method. In this work, we simplified the synthetic procedure of the DPI skeleton with a significant reduction of the synthetic cost by using chromium-mediated cyclization as the key chemistry. Using this method, two DPI-based nonhalogenated D–A copolymers are synthesized. The binary OSCs based on pBDTT-DPI-Me : Y6 achieves a power conversion efficiency as high as 16.55 %, highlighting DPI as an attractive A-unit for further exploration in OSCs.

The residual strain in 2D Ruddlesden–Popper perovskite films is investigated by X-ray diffraction and atomic force microscopy. Strain relaxation facilitated by the organic spacer cations leads to improved film quality, suppressed recombination, and enhanced device performance under external stress.

Abstract

Although the photovoltaic performance of perovskite solar cells (PSCs) has reached the commercial standards, the unsatisfactory stability limits their further application. Hydrophobic interface and encapsulation can block the damage of water and oxygen, while the instability induced by intrinsic residual strain remains inevitable. Here, the residual strain in a two-dimensional (2D) Ruddlesden–Popper (RP) perovskite film is investigated by X-ray diffraction and atomic force microscopy. It's found that the spacer cations contribute to the residual strain even though they are not in the inorganic cages. Benefited from strain relaxation, the film quality is improved, leading to suppressed recombination, promoted charge transport and enhanced efficiency. More significantly, the strain-released devices maintain 86 % of the initial efficiency after being kept in air with 85 % relative humidity (RH) for 1080 h, 82 % under maximum power point (MPP) tracking at 50 °C for 804 h and 86 % after continuous heating at 85 °C for 1080 h.