Chen Weijie

CdSe quantum dots (QDs) are used to modulate the crystallization of CsPbI₂Br films in air. The added QDs with bifunctional ligands play a dual role in not only promoting the nucleation process but also retarding the crystal growth of CsPbI₂Br. Finally, the efficiency of carbon-based CsPbI₂Br solar cells is increased from 12.73% to 14.49%, benefitting from the improved film quality.

The high-quality perovskite film is a prerequisite for high-performance optoelectronic devices. Herein, CdSe colloidal quantum dots (QDs) serve as crystallization seeds for the first time to modulate the nucleation and crystal growth processes simultaneously of the CsPbI₂Br film in the ambient environment. As additives, CdSe QDs help promote the nucleation process in the initial stage of perovskite formation. In addition, it is revealed that the surface ligands of QDs also have an essential influence on the subsequent crystal growth of the perovskite film. The bifunctional ligands on the surface of QDs are beneficial in delaying the growth process of perovskite due to the free functional groups at the ends. The CsPbI₂Br film prepared with bifunctional organic ligand-capped CdSe QD additives shows better crystallinity than that of the inorganic ligand-based one due to the dual function of these kinds of QDs in not only promoting nucleation but also retarding crystal growth of CsPbI₂Br crystals. As a result, the high-quality CsPbI₂Br film with a low defect state density is prepared in the ambient environment. The optimized efficiency of the assembled hole-conductor-free carbon-based perovskite solar cells (C-PSCs) is increased from 12.73% to 14.49%, which is one of the best results for all-inorganic C-PSCs.

A diaminobenzene dihydroiodide-MA_0.6FA_0.4PbI_{3− x} Cl _x analogous 2D unsymmetrical perovskite film is successfully fabricated and applied as absorber layer to further enhance perovskite solar cell (PSC) performance. High power conversion efficiency (PCE) of 22.34% is obtained for MAPbI_{3− x} Cl _x based PSC. The PCE only reduces by 5% under atmospheric humidity of 30%–40% in 140 d.

Abstract

2D perovskites exhibit limited charge transfer and a stable unsymmetrical structure. Hence, a 2D perovskite solar cell (PSC) is more stable but less efficient than a 3D PSC. An effective combination of good stability and high power conversion efficiency (PCE) is desirable in PSCs. A novel diaminobenzene dihydroiodide-MA_0.6FA_0.4PbI_{3− x} Cl _x analogous 2D unsymmetrical perovskite is designed to further enhance PSC performance. The two amino groups of diaminobenzene dihydroiodide (DD) function similarly as the amino groups of methylammonium and formamidinium ions. Therefore, diaminobenzene dihydroiodide can replace methylammonium and formamidinium and create better bonding interaction with the lead trihalide. The analogous 2D unsymmetrical perovskite not only possesses sufficient charge transfer but also exhibits high stability with an appropriate incorporation of DD. Noticeably, the champion device shows a PCE of 22.34%, setting a new record for an MAPbI_{3− x} Cl _x based PSC. The thermal, illumination, and environmental stability is enhanced by 20%–30%. The improved PCE and stability is attributed to better charge transfer and stable structure.

By combining soft-pressing and a multi-functional polymerizable binder (TMTA), MAPbI₃ thick film (≈400 µm) with compact structure, smooth surface, passivated grain boundaries, large area, high uniformity, and state-of-the-art detection performance is achieved. The high-quality perovskite thick film is successfully integrated with back-end thin-film transistor arrays and excellent large-area X-ray imaging is read out.

Abstract

Thanks to its strong X-ray absorption and large carrier diffusion length, perovskites have demonstrated excellent performance for X-ray detection. Combination of perovskite with thin-film transistor (TFT) arrays to construct flat-panel X-ray imager (FPXI) is required for X-ray imaging, yet this is rarely reported. Solution processing of perovskite thick film onto TFT can enable the electronic connection, however the amounts of pinholes inevitably form during the solvent evaporation and result in a porous film with deteriorated performance and stability. Here a novel strategy is raised to achieve high-quality perovskite thick films for TFT integration via soft-pressing and in situ polymerization of multi-functional binder (TMTA). The combined process largely eliminates the pinholes, improves the surface smoothness, passivates grains boundaries, reduces ionic migration, and improves stability. Accordingly, a compact and smooth MAPbI₃ thick film integrating with TFT arrays is prepared for flat-panel X-ray imaging. The largest film (28 × 28 cm²) is obtained with the state-of-the-art performance (ratio of sensitivity to noise current: 1.41 × 10¹¹  µC Gy⁻¹ A⁻¹) among polycrystalline films. It is hoped that the work provides guidance for fabricating compact perovskite thick films and push perovskite FPXI one step further for low-dose X-ray imaging.

Publication date: March 2022

Source: Nano Energy, Volume 93

Author(s): F. De Rossi, B. Taheri, M. Bonomo, V. Gupta, G. Renno, N. Yaghoobi Nia, P. Rech, C. Frost, C. Cazzaniga, P. Quagliotto, A. Di Carlo, C. Barolo, M. Ottavi, F. Brunetti

Highly efficient and stable perovskite solar cells via the two-step method are fabricated by introducing a multifunctional 1,8-octanediamine dihydroiodide (ODADI) layer between electron transport layer and perovskite layer. It is found that the interfacial ODADI layer not only facilitates film crystallization but also reduces the buried-interface defect density, delivering a significant enhancement on device efficiency from 19.87% to 22.07%.

Two-step-processed perovskite solar cells show superior reproducibility in terms of stepwise crystallization management. However, the device performance is limited due to the buried-interface defects that are highly dependent on the diffusion process of organic salts into PbI₂. Herein, 1,8-octanediamine dihydroiodide (ODADI) is adopted to develop an alkylammonium predeposition strategy for the high-quality perovskite film. It is found that the pre-deposited ODADI layer not only facilitates the diffusion of organic salts via interaction with PbI₂, but also passivates the buried-interface defects, resulting in a perovskite film with low defect density, high crystallinity, and superior electronic properties. Consequently, the fabricated devices deliver a significant enhancement on power conversion efficiency (PCE) from 19.87 to 22.07%. In addition, a superior long-term stability in glovebox atmosphere, maintaining 96% of the initial PCE after 1000 h, is demonstrated.

A bulk-heterojunction strategy is developed to reduce the temperature sensitivity of inorganic perovskite solar cells to operation temperature, which may shed light on extending the application of perovskite solar cells for specific scenarios such as polar regions, near space, and exoplanet exploration.

Abstract

Inorganic perovskite solar cells (IPSCs) emerge as an ideal candidate for applications beyond terrestrial implementation due to their robustness. However, underlying mechanisms regarding their photovoltaic process at different temperatures remain unclear. Based on a stable absorber of CsPbI_2.85(BrCl)_0.15, considerable variation of corresponding device performance is revealed over temperature and further demonstrates a simple approach to an effective reduction of such variation. Interestingly, this absorber is found to be excitonic with poor carrier transport even at an ambient temperature of 285 K and below. With a novel device configuration of a PTB7-th/perovskite bulk heterojunction, exciton dissociation and carrier extraction is facilitated. The resultant solar cell attains a best power conversion efficiency (PCE) of 17.2% with the fill factor of ≈84%, which represents the highest-efficiency γ-phase IPSCs reported to date. Importantly, this device is less sensitive to operation temperature, wherein the PCE variation over the temperature range from 210 to 360 K is 60% suppressed compared with the reference. The approach is effectively extended to other IPSCs with different photoactive phases, which may shed light on realizing highly efficient IPSCs for specific scenarios such as polar regions, near-space, and exoplanet exploration.

Highly sensitive self-powered near-infrared circularly polarized light (NIR CPL) detectors are realized using 3D mixed PbSn perovskite embedded with chiral plasmonic gold nanoparticles. The resulting CPL detectors exhibit remarkable discrimination ability for NIR CPL with a high g _res of 0.55 under zero-bias, the highest value in comparison with chiral 2D perovskite-based CPL detectors.

Abstract

Chiral organic ligand-incorporated low-dimensional metal-halide perovskites have received increasing attention for next-generation photodetectors because of the direct detection capability of circularly polarized light (CPL), which overcomes the requirement for subsidiary optical components in conventional CPL photodetectors. However, most chiral perovskites have been based on low-dimensional structures that confine chiroptical responses to the ultraviolet (UV) or short-wavelength visible region and limit photocurrent due to their wide bandgap and poor charge transport. Here, chiroptical properties of 3D Cs_0.05FA_0.5MA_0.45Pb_0.5Sn_0.5I₃ polycrystalline films are achieved by incorporating chiral plasmonic gold nanoparticles (AuNPs) into the mixed PbSn perovskite, without sacrificing its original optoelectronic properties. CPL detectors fabricated using chiral AuNP-embedded perovskite films can operate without external power input; they exhibit remarkable chirality in the near-infrared (NIR) region with a high anisotropy factor of responsivity (g _res) of 0.55, via giant plasmon resonance shift of chiral plasmonic AuNPs. In addition, a CPL detector array fabricated on a plastic substrate demonstrates highly sensitive self-powered NIR detection with superior flexibility and durability.

Solderless stretchable interconnections (SLSIs) are developed to realize the assembly of individual soft devices toward multifunctional all-stretchable integrated platforms. This stretchable interconnection can effectively bridge interlayer conductivity with tight adhesion through regional functionality. SLSIs show promising stretchability up to a strain of 35% (R/R ₀ ≤ 5) and can be adopted to achieve an all-stretchable self-powered data acquisition platform.

Abstract

Stretchable electronics incorporating critical sensing, data transmission, display and powering functionalities, is crucial to emerging wearable healthcare applications. To date, methods to achieve stretchability of individual functional devices have been extensively investigated. However, integration strategies of these stretchable devices to achieve all-stretchable systems are still under exploration, in which the reliable stretchable interconnection is a key element. Here, solderless stretchable interconnections based on mechanically interlocking microbridges are developed to realize the assembly of individual stretchable devices onto soft patternable circuits toward multifunctional all-stretchable platforms. This stretchable interconnection can effectively bridge interlayer conductivity with tight adhesion through both conductive microbridges and selectively distributed adhesive polymer. Consequently, enhanced stretchability up to a strain of 35% (R/R ₀ ≤ 5) is shown, compared with conventional solder-assisted connections which lose electrical conduction at a strain of less than 5% (R/R ₀ ≈ 30). As a proof of concept, a self-powered all-stretchable data-acquisition platform is fabricated by surface mounting a stretchable strain sensor and a supercapacitor onto a soft circuit through solderless interconnections. This solderless interconnecting strategy for surface-mountable devices can be utilized as a valuable technology for the integration of stretchable devices to achieve all-soft multifunctional systems.

Publication date: 10 February 2022

Source: Electrochimica Acta, Volume 405

Author(s): Shicheng Tang, Jingan Chen, Chi Li, Ziwen Mao, Zhibin Cheng, Jindan Zhang, Mengqi Zhu, Shengchang Xiang, Zhangjing Zhang

Stabilizing the black phases of CsPbI₃ perovskite is the most crucial challenge to realizing highly stable and efficient inorganic perovskite solar cells. It is found that adding multidimensional zwitterions leads to the formation of pinhole-free films, and suppression of the δ-phase of CsPbI₃. In addition, the thermal aging test at 100 °C indicates excellent phase stability of perovskites at high temperatures.

Abstract

All-inorganic cesium lead iodide (CsPbI₃) perovskites, which replace volatile and hygroscopic organic components with stable inorganic cesium cations, have promising photoelectronic properties for potential application in solar cells. However, highly stable and efficient CsPbI₃-based perovskite solar cells are rarely reported because the optically active black phases of CsPbI₃ tend to change into a photo-inactive yellow δ-phase. Herein, a highly stable CsPbI₃ film that is formed by introducing a small quantity of zwitterions with different dimensions to the perovskite precursor solution is reported. The zwitterions effectively inhibit the formation of the yellow δ-phase during perovskite crystallization and promote the development of a stable black α-phase. In addition, a systematic analysis reveals strong interaction between 3D zwitterions and perovskites in both the solution and film states, which leads to a dense and pinhole-free CsPbI₃ film with suppressed trap states. The resulting perovskite solar cells with 3D zwitterions achieve a significantly improved power conversion efficiency of 18.4% with high reproducibility. The devices without encapsulation retain 98% of the initial efficiency after 25 days at 25 °C and relative humidity of 25% ± 5%. Importantly, the 3D zwitterion-based devices demonstrate excellent phase stability when subjected to thermal aging at 100 °C.

5-chloroindole (Cl-indole) is introduced into the interface between SnO₂ and perovskite. Cl-indole can form hydrogen bonds with iodine in the perovskite and can also coordinate and passivate Pb²⁺ and Sn⁴⁺ defects to alleviate carrier nonradiative recombination. The pristine device reaches an efficiency of 20.58%, while the modified device achieves an efficiency of 22.47%, along with improved hysteresis effect and stability.

Interface engineering has been proven to be an effective method to improve the performance and stability of perovskite solar cells (PSCs). Herein, 5-chloroindole (Cl-indole) is introduced into the interface of a SnO₂ electron transport layer and perovskite light-absorbing layer to improve the photovoltage performance of the device. The results show that Cl−indole can not only form hydrogen bonds with iodine in the perovskite to optimize the interface contact but also coordinate and passivate the Pb²⁺ and Sn⁴⁺ interface defects to alleviate carrier nonradiative recombination. Compared with the pristine SnO₂-based planar PSCs with a power conversion efficiency (PCE) of 20.58%, the Cl−indole-modified SnO₂-based device achieves a PCE of 22.47%. Meanwhile, the stability of the modified device is effectively improved and the hysteresis effect is reduced. This work demonstrates a promising strategy for high-efficient and stable PSCs by optimizing interface contact and passivating interface defects.

Publication date: 19 January 2022

Source: Joule, Volume 6, Issue 1

Author(s): Zhong Zheng, Jianqiu Wang, Pengqing Bi, Junzhen Ren, Yafei Wang, Yi Yang, Xiaoyu Liu, Shaoqing Zhang, Jianhui Hou

Monolithic metal-halide perovskite tandem solar cells reach a power conversion efficiency of 23% after passivating the interfaces of the wide- and narrow-bandgap perovskites with the C₆₀ electron transport layer and minimizing the optical losses in the cell by using a hydrogenated indium oxide front contact and a thin hole transporting layers.

Abstract

Perovskite-based multijunction solar cells are a potentially cost-effective technology that can help surpass the efficiency limits of single-junction devices. However, both mixed-halide wide-bandgap perovskites and lead-tin narrow-bandgap perovskites suffer from non-radiative recombination due to the formation of bulk traps and interfacial recombination centers which limit the open-circuit voltage of sub-cells and consequently of the integrated tandem. Additionally, the complex optical stack in a multijunction solar cell can lead to losses stemming from parasitic absorption and reflection of incident light which aggravates the current mismatch between sub-cells, thereby limiting the short-circuit current density of the tandem. Here, an integrated all-perovskite tandem solar cell is presented that uses surface passivation strategies to reduce non-radiative recombination at the perovskite-fullerene interfaces, yielding a high open-circuit voltage. By using optically benign transparent electrode and charge-transport layers, absorption in the narrow-bandgap sub-cell is improved, leading to an improvement in current-matching between sub-cells. Collectively, these strategies allow the development of a monolithic tandem solar cell exhibiting a power-conversion efficiency of over 23%.

A novel ionic liquid, 1-ethyl-3-methylimidazolium hydrogen sulfate (EMIMHSO₄), is employed for managing defects in printed cesium lead triiodide (CsPbI₃) films. The EMIMHSO₄ can succesfully regulate perovskite thin-film growth and strongly coordinate with the undercoordinated Pb²⁺, which enable the achievement of the highest-efficiencies ambient printed CsPbI₃ solar cells, both under 1 sun illumination (20.01%, 100 mW cm⁻²) and indoor light illumination (37.24%, 1000 lux, 365 µW cm⁻²).

Abstract

All-inorganic cesium lead triiodide (CsPbI₃) perovskite is well known for its unparalleled stability at high temperatures up to 500 °C and under oxidative chemical stresses. However, upscaling solar cells via ambient printing suffers from imperfect crystal quality and defects caused by uncontrollable crystallization. Here, the incorporation of a low concentration of novel ionic liquid is reported as being promising for managing defects in CsPbI₃ films, interfacial energy alignment, and device stability of solar cells fabricated via ambient blade-coating. Both theoretical simulations and experimental measurements reveal that the ionic liquid successfully regulates the perovskite thin-film growth to decrease perovskite grain boundaries, strongly coordinates with the undercoordinated Pb²⁺ to passivate iodide vacancy defects, aligns the interface to decrease the energy barrier at the electron-transporting layer, and relaxes the lattice strain to promote phase stability. Consequently, ambient printed CsPbI₃ solar cells with power conversion efficiency as high as 20.01% under 1 sun illumination (100 mW cm⁻²) and 37.24% under indoor light illumination (1000 lux, 365 µW cm⁻²) are achieved; both are the highest for printed all-inorganic cells for corresponding applications. Furthermore, the bare cells show an impressive long-term ambient stability with only ≈5% PCE degradation after 1000 h aging under ambient conditions.