Chen Weijie

A zwitterion formamidine sulfinic acid (FSA) is deposited at the tin(IV) oxide (SnO₂)/perovskite interface to induce the crystallization of high-quality black-phase formamidinium lead iodide (FAPbI₃), and also help reduce the side effect of the residual lead iodide (PbI₂), yielding an impressive power conversion efficiency (PCE) of 24.1% and 1000 h long-term operational stability.

Abstract

Black-phase formamidinium lead iodide (FAPbI₃) with narrow bandgap and high thermal stability has emerged as the most promising candidate for highly efficient and stable perovskite photovoltaics. In order to overcome the intrinsic difficulty of black-phase crystallization and to eliminate the lead iodide (PbI₂) residue, most sequential deposition methods of FAPbI₃-based perovskite will introduce external ions like methylammonium (MA⁺), cesium (Cs⁺), and bromide (Br^–) ions to the perovskite structure. Here a zwitterion-functionalized tin(IV) oxide (SnO₂) is introduced as the electron-transport layer (ETL) to induce the crystallization of high-quality black-phase FAPbI₃. The SnO₂ ETL treated with the zwitterion of formamidine sulfinic acid (FSA) can help rearrange the stack direction, orientation, and distribution of residual PbI₂ in the perovskite layer, which reduces the side effect of the residual PbI₂. Besides, the FSA functionalization also modifies SnO₂ ETL to suppress deep-level defects at the perovskite/SnO₂ interface. As a result, the FSA–FAPbI₃-based perovskite solar cells (PSCs) exhibit an excellent power conversion efficiency of up to 24.1% with 1000 h long-term operational stability. These findings provide a new interface engineering strategy on the sequential fabrication of black-phase FAPbI₃ PSCs with improved optoelectronic performance.

A pseudosymmetric electron acceptor, BS3TSe-4F, designed from asymmetric selenium substitution strategy promotes free charge generation to enhance exciton dissociation and suppress energy loss in sequentially processed organic solar cells, leading to a record power conversion efficiency of over 19%.

Abstract

A record power conversion efficiency (PCE) of over 19% is realized in planar-mixed heterojunction (PMHJ) organic solar cells (OSCs) by adopting the asymmetric selenium substitution strategy in making a pseudosymmetric electron acceptor, BS3TSe-4F. The combined molecular asymmetry with more polarizable selenium substitution increases the dielectric constant of the D18/BS3TSe-4F blend, helping lower the exciton binding energy. On the other hand, dimer packing in BS3TSe-4F is facilitated to enable free charge generation, helping more efficient exciton dissociation and lowering the radiative recombination loss (ΔE ₂) of OSCs. As a result, PMHJ OSCs based on D18/BS3TSe-4F achieve a PCE of 18.48%. By incorporating another mid-bandgap acceptor Y6-O into D18/BS3TSe-4F to form a ternary PMHJ, a higher open-circuit voltage (V _OC) can be achieved to realize an impressive PCE of 19.03%. The findings of using pseudosymmetric electron acceptors in enhancing device efficiency provides an effective way to develop highly efficient acceptor materials for OSCs.

A highly crystalline tempered-glass-like perovskite with compressed surface lattice-structure can be made by a thermal-shocking fabrication process, which significantly enhances the ionic activation temperature and contributes to hysteresis-free operation of perovskite solar cells (PSCs) at high temperature up to 363 K, enabling efficient and stable PSCs fabricated by a high-speed post-annealing-free process in air with the scalable bar-coating technique.

Abstract

A highly crystalline tempered-glass-like perovskite grain structure with compressed surface lattice realized by a thermal-shocking fabrication is shown. The strained perovskite grain structure is stabilized by Cl⁻-reinforcing surface lattice and shows enhanced bonding energy and ionic activation temperature, which contributes to hysteresis-free operation of perovskite solar cells (PSCs) at much higher temperature up to 363 K in thermal-shocking-processed MAPbCl _x I_{3− x} (T-MPI). The PSCs can be fabricated by a high-speed fully air process without post-annealing based on the scalable bar-coating technique. Both high efficiency and stability are achieved in T-MPI PSC with a power conversion efficiency (PCE) up to 22.99% and long-term operational stability with T ₈₀ lifetime exceeding 4000 h.

Organic solar cells (OSCs) have experienced rapid progress with the innovation of near-infrared-absorbing small-molecular acceptors. This work prescribes a facile, cost-effective, and scalable method for the preparation of high-performance fluorinated perylene-diimide as cathode interlayers, making OSCs more promising.

Abstract

Organic solar cells (OSCs) have experienced rapid progress with the innovation of near-infrared (NIR)-absorbing small-molecular acceptors (SMAs), while the unique electronic properties of the SMAs raise new challenges in relation to cathode engineering for effective electron collection. To address this issue, two fluorinated perylene-diimides (PDIs), PDINN-F and PDINN-2F, are synthesized by a simple fluorination method, for application as cathode interlayer (CIL) materials. The two bay-fluorinated PDI-based CILs possess a lower lowest unoccupied molecular orbital (LUMO) energy level of ≈−4.0 eV, which improves the energy level alignment at the NIR-SMAs (such as BTP-eC9)/CIL for a favorable electron extraction efficiency. The monofluorinated PDINN-F shows higher electron mobility and better improved interfacial compatibility. The PDINN-F-based OSCs with PM6:BTP-eC9 as active layer exhibit an enhanced fill factor and larger short-circuit current density, leading to a high power conversion efficiency (PCE) exceeding 18%. The devices with PDINN-F CIL retain more than 80% of their initial PCE after operating at the maximum power point under continuous illumination for 750 h. This work prescribes a facile, cost-effective, and scalable method for the preparation of stable, high-performance fluorinated CILs, and instilling promise for the NIR-SMAs-based OSCs moving forward.

Publication date: September 2022

Source: Nano Energy, Volume 100

Author(s): Zicheng Li, Can Wang, Ping-Ping Sun, Zhihao Zhang, Qin Zhou, Yitian Du, Jianbin Xu, Yibo Chen, Qiu Xiong, Liming Ding, Mohammad Khaja Nazeeruddin, Peng Gao

Publication date: October 2022

Source: Journal of Energy Chemistry, Volume 73

Author(s): Xuejiao Zuo, Yiyang He, Hongyu Ji, Yong Li, Xiuying Yang, Binxun Yu, Tao Wang, Zhike Liu, Wenliang Huang, Jing Gou, Ningyi Yuan, Jianning Ding, Shengzhong Frank Liu

Publication date: August 2022

Source: Applied Materials Today, Volume 28

Author(s): Yuqiong Huang, Hao Luo, Baohao Zhang, Kuo Su, Wentao Chen, Guomin Sui, Lusheng Liang, Bao Zhang, Jian Song, Peng Gao

A precursor stabilization and defect passivation strategy was developed by employing 3-hydrazinobenzoic acid (3-HBA) as a versatile additive. The synergistic effect of −NHNH₂ and −COOH suppresses oxidation of I⁻, deprotonation of organic cations and amine-cation reaction. The NiO _x -based inverted device achieves a certified efficiency of 23.3 % with excellent operational stability.

Abstract

Perovskite solar cells suffer from poor reproducibility due to the degradation of perovskite precursor solution. Herein, we report an effective precursor stabilization strategy via incorporating 3-hydrazinobenzoic acid (3-HBA) containing carboxyl (−COOH) and hydrazine (−NHNH₂) functional groups as stabilizer. The oxidation of I⁻, deprotonation of organic cations and amine-cation reaction are the main causes of the degradation of mixed organic cation perovskite precursor solution. The −NHNH₂ can reduce I₂ defects back to I⁻ and thus suppress the oxidation of I⁻, while the H⁺ generated by −COOH can inhibit the deprotonation of organic cations and subsequent amine-cation reaction. The above degradation reactions are simultaneously inhibited by the synergy of functional groups. The inverted device achieves an efficiency of 23.5 % (certified efficiency of 23.3 %) with an excellent operational stability, retaining 94 % of the initial efficiency after maximum power point tracking for 601 hours.

Publication date: September 2022

Source: Nano Energy, Volume 100

Author(s): Zeyu Song, Jihuai Wu, Liuxue Sun, Tingting Zhu, Chunyan Deng, Xiaobing Wang, Guodong Li, Yitian Du, Qi Chen, Weihai Sun, Leqing Fan, Hongwei Chen, Jianming Lin, Zhang Lan

A novel amino-functionalized fullerene derivative (C ₆₀-BPAM) is synthesized and applied as an ‘improbable’ spacer cation for 2D/3D hybrid perovskite affording enhanced electron transport, which represents the first fullerene spacer and the largest aromatic spacer applicable in 2D/3D perovskite solar cells (PSCs). Incorporation of C ₆₀-BPAM²⁺ spacer bearing highly conductive fullerene tail leads to increased PCE of 2D/3D PSCs from 19.36% to 20.21% along with significantly improved humidity stability.

Abstract

2D perovskites possess superior humidity stability but inferior power conversion efficiency (PCE) compared with 3D perovskites due to their typically insulating spacers. Size of the spacer cation is determinative for the formation of 2D perovskite, and fullerene is believed not to be capable of templating 2D perovskite structure because of its larger size than the width of the lead-halide octahedron despite its well-known strong electron-accepting ability. Herein, a novel amino-functionalized fullerene derivative (abbreviated as C₆₀-BPAM) is developed and an ‘improbable’ spacer for 2D/3D hybrid perovskite solar cells (PSCs), achieving enhanced electron transport is applied. Unlike most of the reported alkylammonium spacers that are based on insulating organic tails, the incorporation of a highly conductive fullerene tail within C₆₀-BPAM²⁺ leads to increased electron density in 2D/3D perovskite and induces an additional built-in electric field, facilitating electron transport in PSCs. Besides, the 2D/3D hybrid structure helps to passivate both of the shallow- and deep-level defects within perovskite. As a result, the PCE of 2D/3D PSCs improves from 19.36% (3D MAPbI₃ PSCs) to 20.21%. Moreover, the 2D/3D PSCs show significant improvement in the humidity stability compared to the 3D counterparts.

Two isomeric small-molecule acceptors of ThPy5 and ThPy6 are developed by moving the thiophene position of the central core in IDTP-4F, and the organic solar cells based on PM6:ThPy6 achieve a power conversion efficiency as high as 16.11% with an excellent fill factor of 0.789.

Abstract

Moving one subunit of the central core to the other side in a small-molecule acceptor (SMA) is an effective approach to achieve the goal of isomerization, which has proven viable to enhance photovoltaic performance. Herein, two isomeric SMAs of ThPy5 and ThPy6 are developed by changing the position of the thiophene unit of the dithieno[3,2-b:2′,3′-d]pyrrol in IDTP-4F. The effect of altering the thiophene position on morphological characteristics, macroscopic factors, and device performance is thoroughly investigated among these three isomeric SMAs. Compared to ThPy5, IDTP-4F and ThPy6 show planar molecular structures and better molecular orientation. Moreover, tighter π–π stacking as well as enhanced electron mobility is observed in ThPy6 relative to IDTP-4F. PM6:ThPy6-based organic solar cells (OSCs) achieve the maximum efficiency of 16.11%, along with an excellent fill factor (FF) of 0.789, which are among the best results for A-D-A-type SMA-based OSCs. The high FF ascribes to the improved molecular packing and charge collection/extraction efficacy and the reduced charge recombination. The structure–morphology–performance relationship drawn from this work can offer better guidance for designing the molecular structure, especially the central cores of SMAs.

Random copolymerization, which can reduce molecular regio-regularity and enhance the solubility, is purposefully utilized to fabricate high-performance nonhalogenated processed polymer donors. Additionally, the terpolymers display a temperature-dependent aggregation feature, thus the phase morphology of the active layer is effectively controlled. Finally, organic solar cells based on terpolymer (PL1) exhibit a power conversion efficiency of 18.14% with a low nonradiative energy loss.

Abstract

Three terpolymer donors (PL1, PL2, and PL3) employing repeating units of two popular photovoltaic polymers PM6 and D18 are synthesized by random copolymerization. The terpolymers can reduce the regio-regularity of the polymer backbones and endow them with much-enhanced solubility in nonhalogenated solvents such as o-xylene. Furthermore, along with the appearance of temperature-dependent aggregation behavior, indicating the adaptability for fabricating organic solar cells (OSCs) by eco-friendly solvent processing. Among them, PL1-based OSCs display higher and more balanced hole and electron mobilities, longer charge separation exciton lifetime, and better exciton dissociation and charge collection capabilities than the parent polymers (PM6 and D18) based ones. A power conversion efficiency of   18.14% with a very low energy loss is achieved based on terpolymer PL1, which is much higher than that of PM6 (15.16%) and D18 (16.18%). The result provides an effective way to realize high-performance nonhalogenated processing polymer donor materials.

Ink engineering plays an important role in blade-coated large-area perovskite solar cells (PSCs). In this review, the perovskite ink engineering for blade-coated PSCs is systematically summarized, including perovskite composition management, solvent engineering, and additive strategy to passivate perovskite defects. Moreover, recent advances in functional layer ink engineering, fully blade-coated PSCs, and hole transporting material-free carbon-based PSCs are summarized.

Abstract

To date, organic–inorganic hybrid perovskite solar cells (PSCs) have reached a certified efficiency of 25.7%, showing great potential in upscale industrial commercialization. However, a huge obstacle facing the industrialization of PSCs is the decreased efficiency and long-term stability when upscaling the device area. To overcome these issues, blade-coating methods have been developed to fabricate large-area PSCs due to their capability to deposit uniform large-area perovskite films. Ink engineering plays an important role in the blade-coating, especially for crystallinity and defect control. In this review, the blade-coating method to fabricate large-area perovskite films is first introduced. Then, the perovskite ink engineering for blade-coating PSCs is systematically summarized. Specifically, the effects of perovskite composition management and solvent engineering on perovskite film quality are discussed, and recent efforts in additive strategy to passivate perovskite defects are also summarized. Subsequently, recent advances in functional layer ink engineering and fully blade-coated PSCs are summarized. Moreover, the applications of blade-coating method in hole transporting material-free carbon-based PSCs are discussed. Finally, some suggestions and an outlook on this field are provided to help facilitate highly efficient and stable blade-coated PSCs.

A formamidinium methylammonium lead iodide (FAMAPbI₃) perovskite is reported that is passivated by bifunctional methyl bromoacetate (MBrA), which has a strong interaction with Pb²⁺ by forming a dimer complex ([C₆H₁₀Br₂O₄Pb]²⁺) to reduce defect density and suppress non-radiative recombination; the Br⁻ in MBrA can passivate iodine-related defects. The MBrA-modified-device achieves efficiency of 24.29% that is one of the best values for FAMAPbI₃-based devices.

Abstract

Formamidinium methylammonium lead iodide (FAMAPbI₃) perovskite has been intensively investigated as a potential photovoltaic material because it has higher phase stability than its pure FAPbI₃ perovskite counterpart. However, its power conversion efficiency (PCE) is significantly inferior due to its high density of surface detects and mismatched energy level with electrodes. Herein, a bifunctional passivator, methyl haloacetate (methyl chloroacetate, (MClA), methyl bromoacetate (MBrA)), is designed to reduce defect density, to tune the energy levels and to improve interfacial charge extraction in the FAMAPbI₃ perovskite cell by synergistic passivation of both CO groups and halogen anions. As predicted by modeling undercoordinated Pb²⁺, the MBrA shows a very strong interaction with Pb²⁺ by forming a dimer complex ([C₆H₁₀Br₂O₄Pb]²⁺), which effectively reduces the defect density of the perovskite and suppresses non-radiative recombination. Meanwhile, the Br⁻ in MBrA passivates iodine-deficient defects. Consequently, the MBrA-modified device presents an excellent PCE of 24.29%, an open-circuit voltage (V _oc) of 1.18 V (V _oc loss ≈ 0.38 V), which is one of the highest PCEs among all FAMAPbI₃-based perovskite solar cells reported to date. Furthermore, the MBrA-modified devices without any encapsulation exhibit remarkable long-term stability with only 9% of PCE loss after exposure to ambient air for 1440 h.

A single-dot perovskite spectrometer is demonstrated, which first breaks the long-standing restriction of footprint-resolution. The control of ion migration in the perovskite is the key of the spectrum richness and cyclic stability. Without any optical and mechanical structure, the spectrum can be recognized by a single detector through the bias stimulated photogain modulation.

Abstract

There are significant applications for miniature on-chip spectrometers in many fields. However, at present, on-chip spectrometers have to utilize an integrated strategy to achieve spectral analysis, which undoubtedly squanders the photosensitive area and adds pressure to the miniaturization of the spectrometer. Here, a unique spectrometer design that adopts a single detection point with in situ modulation realized by the photogain control at various bias voltages is demonstrated. With micrometer-level footprints, this single-dot spectrometer processes a resolution of about 5 nm and a response time down to about 197 µs. This is the first in situ perovskite modulation strategy that breaks the footprint-resolution restriction of spectrum analysis and demonstrates a new design direction for functional perovskite devices.

3D printing of flexible microelectronics has gained significant attention. In this work, a photosensitive resin doped with organic semiconductor material is developed for direct laser writing based on multiphoton lithography. Fabrication of microelectronic devices, hybrid microelectrodes, cell-adhesive substrates, and high-performance glucose biosensors are successfully demonstrated. These soft and conductive microstructures have potential in flexible electronics, organic bioelectronics, and biosensors.

Abstract

In recent years, 3D printing of electronics have received growing attention due to their potential applications in emerging fields such as nanoelectronics and nanophotonics. Multiphoton lithography (MPL) is considered the state-of-the-art amongst the microfabrication techniques with true 3D fabrication capability owing to its excellent level of spatial and temporal control. Here, a homogenous and transparent photosensitive resin doped with an organic semiconductor material (OS), which is compatible with MPL process, is introduced to fabricate a variety of 3D OS composite microstructures (OSCMs) and microelectronic devices. Inclusion of 0.5 wt% OS in the resin enhances the electrical conductivity of the composite polymer about 10 orders of magnitude and compared to other MPL-based methods, the resultant OSCMs offer high specific electrical conductivity. As a model protein, laminin is incorporated into these OSCMs without a significant loss of activity. The OSCMs are biocompatible and support cell adhesion and growth. Glucose-oxidase-encapsulated OSCMs offer a highly sensitive glucose sensing platform with nearly tenfold higher sensitivity compared to previous glucose biosensors. In addition, this biosensor exhibits excellent specificity and high reproducibility. Overall, these results demonstrate the great potential of these novel MPL-fabricated OSCM devices for a wide range of applications from flexible bioelectronics/biosensors, to nanoelectronics and organ-on-a-chip devices.

Publication date: 20 July 2022

Source: Joule, Volume 6, Issue 7

Author(s): Michele De Bastiani, Anand S. Subbiah, Maxime Babics, Esma Ugur, Lujia Xu, Jiang Liu, Thomas G. Allen, Erkan Aydin, Stefaan De Wolf

Publication date: 20 July 2022

Source: Joule, Volume 6, Issue 7

Author(s): Jianxing Xia, Yi Zhang, Chuanxiao Xiao, Keith Gregory Brooks, Min Chen, Junsheng Luo, Hua Yang, Nadja Isabelle Desiree Klipfel, Jihua Zou, Yu Shi, Xiaojun Yao, Jiangzhao Chen, Joseph M. Luther, Hongzhen Lin, Abdullah M. Asiri, Chunyang Jia, Mohammad Khaja Nazeeruddin

Publication date: 20 July 2022

Source: Joule, Volume 6, Issue 7

Author(s): Jin Hyuck Heo, Fei Zhang, Jin Kyoung Park, Hyong Joon Lee, David Sunghwan Lee, Su Jeong Heo, Joseph M. Luther, Joseph J. Berry, Kai Zhu, Sang Hyuk Im

Active layers for (semi-)transparent organic photovoltaics (ST-OPVs) must meet high transparency requirements for integrated energy-harvesting solutions. A pathway towards high visible transparency is combining a near-infrared-absorbing acceptor material with small fractions of a visible-light-absorbing donor component. An in-depth analysis of three blend systems yields an in-depth understanding of the device physics upon reduction of the donor.

Abstract

The charge generation–recombination dynamics in three narrow-bandgap near-IR absorbing nonfullerene (NFA) based organic photovoltaic (OPV) systems with varied donor concentrations of 40%, 30%, and 20% are investigated. The dilution of the polymer donor with visible-range absorption leads to highly transparent active layers with blend average visible transmittance (AVT) values of 64%, 70%, and 77%, respectively. Opaque devices in the optimized highly reproducible device configuration comprising these transparent active layers lead to photoconversion efficiencies (PCEs) of 7.0%, 6.5%, and 4.1%. The investigation of these structures yields quantitative insights into changes in the charge generation, non-geminate charge recombination, and extraction dynamics upon dilution of the donor. Lastly, this study gives an outlook for employing the highly transparent active layers in semitransparent organic photovoltaics (ST-OPVs).