Chen Weijie

A low parasitic absorption with high thickness‐insensitivity feature can be concurrently achieved with the incorporation of zirconium (Zr) element into ZnO thin film (ZnO:Zr). Moreover, optimized surface morphology and enhanced electron conductivity are proposed in ZnO:Zr film. Indeed, ZnO:Zr electron transporting layers (ETL) boost the photovoltaic performance up to 17.2% with an improvement over 9% than that of pristine ZnO‐based devices (15.7%).

Abstract

Solution‐processed zinc oxide (ZnO) is one of the widely used electron transporting layers (ETLs) for organic solar cells (OSCs). However, low optical transparency along with thickness‐sensitivity of ZnO ETL constrains the improvement of photovoltaic performance and large‐scale fabrication compatibility. To resolve these issues, zirconium (Zr) doping is applied to tailor the optoelectronic and morphological properties of ZnO layer. This approach not only improves light transmittance with the suppressed parasitic absorption, but also provides an optimized surface morphology for enhancing charge extraction property and reducing potential of charge trap‐assisted recombination. By using ZnO:Zr as ETL in inverted device configuration, the maximum power conversion efficiency (PCE) of PM6:Y6:PC₇₁BM solar cell devices is up to 17.2%, which makes an enhancement of 9.55% compared to ZnO‐based devices (15.7%). As the thickness of ZnO:Zr ETL increases to ≈60 nm, the presence of the lower parasitic absorption together with uniform surface morphology can help photovoltaic performance maintain above 15%, which is beyond the performance of the pristine ZnO‐based device achieving only 11.9%. Such superiority of ZnO:Zr ETL is also validated by a series of well‐known BHJ systems, where in comparison with the devices based on pristine ZnO ETL, a better photovoltaic performance from ZnO:Zr device can be achieved.

Nature Communications, Published online: 20 January 2021; doi:10.1038/s41467-020-20791-z

Publication date: April 2021

Source: Nano Energy, Volume 82

Author(s): D. Saranin, S. Pescetelli, A. Pazniak, D. Rossi, A. Liedl, A. Yakusheva, L. Luchnikov, D. Podgorny, P. Gostischev, S. Didenko, A. Tameev, D. Lizzit, M. Angelucci, R. Cimino, R. Larciprete, A. Agresti, A. Di Carlo

Publication date: May 2021

Source: Nano Energy, Volume 83

Author(s): Tao Ye, Kai Wang, Shaoyang Ma, Congcong Wu, Yuchen Hou, Dong Yang, Ke Wang, Shashank Priya

Publication date: May 2021

Source: Nano Energy, Volume 83

Author(s): Sergey Tsarev, Selina Olthof, Aleksandra G. Boldyreva, Sergey M. Aldoshin, Keith J. Stevenson, Pavel A. Troshin

Publication date: 20 January 2021

Source: Joule, Volume 5, Issue 1

Author(s): Tianqi Niu, Weiya Zhu, Yiheng Zhang, Qifan Xue, Xuechen Jiao, Zijie Wang, Yue-Min Xie, Ping Li, Runfeng Chen, Fei Huang, Yuan Li, Hin-Lap Yip, Yong Cao

Publication date: 11 March 2021

Source: Chem, Volume 7, Issue 3

Author(s): Fei Zhang, Haipeng Lu, Bryon W. Larson, Chuanxiao Xiao, Sean P. Dunfield, Obadiah G. Reid, Xihan Chen, Mengjin Yang, Joseph J. Berry, Matthew C. Beard, Kai Zhu

Crystalline, dense and uniform perovskite thin films are crucial for achieving high power conversion efficiency solar cells. Here, we demonstrated a universal method of fabricating highly crystalline and large‐grain perovskite films via crystal engineering. We applied anion exchange of Cl⁻ and I⁻, and annealing perovskite films, in an ultra‐confined and uniform temperature enclosed space with saturated MAI (or FAI) vapor using hot‐pressing sublimation technology. This process ensures a rapid crystal growth rate due to fast exchange between the gas phase and the crystalline film to reduce vertically oriented grain boundaries. The generation of the commonly observed PbI₂ phase is also suppressed due to the chemical equilibrium state during the thermal annealing process. Using this approach, pinhole‐free perovskite films with preferred crystal orientation and micrometer‐scale grains were obtained, leading to a high steady‐state efficiency of 22.15% based on mixed cation perovskite composition. In addition, devices based on different perovskite compositions all exhibited enhanced photovoltaic performance based on the crystal engineering method. The device (without encapsulation) had an efficiency loss of about only 4% after 2520‐hour aging in ambient conditions and retained 87% of its initial efficiency after 1000‐hour continuous one‐sun light soaking, thus demonstrating considerably improved stability.

This article is protected by copyright. All rights reserved.

In this work, it is demonstrated, by using industrial techniques that a passivation layer with nanocontacts based on silicon oxide (SiO_x) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se₂ (CIGS) solar cells. Two approaches were applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 ºC and 500 ºC, the SiO_x passivation layer demonstrates positive passivation properties, which were supported by electrical simulations. Such positive effects led to an increase of the light to power conversion efficiency value of 2.6 % (absolute value) for passivated devices compared to a non‐passivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade‐off between passivation effect and charge extraction, as demonstrated by the trade‐off between V_oc and J_sc compared to FF. For the first time, a fully‐industrial up‐scalable process combining SiO_x as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results towards high‐performance and low‐cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12 %, demonstrating the potential of SiO_x as a passivation material for energy conversion devices.

This article is protected by copyright. All rights reserved.

A chlorinated π‐conjugated donor polymer with a siloxane‐functionalized side chain is developed and utilized in binary‐ and ternary‐based nonfullerene organic solar cells processed using a nonhalogenated solvent (toluene), which achieve high power conversion efficiencies of 10.38% and 13.25%, respectively. The thickness of the ternary blend is 300 nm. Furthermore, the binary‐ and ternary‐based devices exhibit high thermal and atmospheric stabilities.

Although several donor polymers have been synthesized for use in nonfullerene organic solar cells (NFOSCs), the number of efficient π‐conjugated donor polymers compatible with nonhalogenated solvent‐processed thick active layer NFOSCs is limited. Two wide‐bandgap π‐conjugated donor polymers functionalized with a siloxane side chain, P1 (chlorine‐free) and P2 (chlorinated), are designed and synthesized. The siloxane‐functionalized side chains and/or Cl π‐conjugated donor polymers increase the absorption coefficients, reduce the energy losses, increase the charge‐carrier mobility, and suppress the bimolecular recombination, which are beneficial to achieve high‐performance thick‐film ternary NFOSCs. Toluene‐processed devices based on P2:IT‐4F:BTP‐4Cl, and P2:IT‐4F:BTP‐4F exhibit high power conversion efficiencies (PCEs) of 13.25% and 11.02% with fill factors (FFs) of 70.03% and 71.60%, respectively. A P2:IT‐4F binary NFOSC exhibits a PCE of 10.38% with an FF of 69.78%, lower than that of the ternary NFOSC. The ternary device PCE of 13.25% is achieved using a 300 nm‐thick active layer, indicating that the siloxane‐functionalized side‐chain π‐conjugated polymer easily controls the bulk heterojunction blend film thickness of the NFOSC. The findings may potentially aid the development of nonhalogenated solvent‐processed thick‐film ternary NFOSCs that can satisfy future production requirements.

The significant advances in efficient photoabsorbent materials have been instrumental in the performance enhancement of semitransparent organic solar cells (ST‐OSCs) from <7% to 12–14% (with good visible transmittance) only in the last 3 years. This study reviews the progress of photoabsorbent materials for ST‐OSCs, and discusses the structure–property relationships and future perspectives for the development of multifunctional ST‐OSCs.

Abstract

Semi‐transparent organic solar cells (ST‐OSCs) have revolutionized the field of photovoltaics (PVs) due to their unique abilities, such as transparency and color tunability, and have transformed normal power‐harvesting OSC devices into multifunctional devices, such as building‐integrated photovoltaics, agrivoltaics, floating photovoltaics, and wearable electronics. Very recently, ST‐OSCs have seen remarkable progress, with a rapid increase in power conversion efficiency from below 7% to 12–14%, with an average visible transparency of 9–25%, especially due to the use of low bandgap semiconductors including polymer donors and non‐fullerene acceptors that exhibit absorption in the near‐infrared region as photoabsorbent materials. From this perspective, the latest developments in ST‐OSCs stemming from the innovations in photovoltaic materials that delivered multifunctional ST‐OSCs with top‐of‐the‐line power conversion efficiencies are discussed to shed light on the structure‐property relationship between molecular design and current challenges in this cutting‐edge research field. Finally, personal perspectives, including research directions for the future use of ST‐OSCs in multifunctional applications, are also proposed.

Organic photovoltaics have long promised low embodied energy, low cost solar power but have yet to make the commercial transition. Recent advances in efficiencies are potentially about to change this status‐quo, driven by a new class of semiconductors called the non‐fullerene electron acceptors. The emergence of these materials is reviewed, and perspectives provided as to future challenges and performance.

Abstract

Organic solar cells are composed of electron donating and accepting organic semiconductors. Whilst a significant palette of donors has been developed over three decades, until recently only a small number of acceptors have proven capable of delivering high power conversion efficiencies. In particular the fullerenes have dominated the landscape. In this perspective, the emergence of a family of materials–the non‐fullerene acceptors (NFAs) is described. These have delivered a discontinuous advance in cell efficiencies, with the significant milestone of 20% now in sight. Intensive international efforts in synthetic chemistry have established clear design rules for molecular engineering enabling an ever‐expanding number of high efficiency candidates. However, these materials challenge the accepted wisdom of how organic solar cells work and force new thinking in areas such as morphology, charge generation and recombination. This perspective provides a historical context for the development of NFAs, and also addresses current thinking in these areas plus considers important manufacturability criteria. There is no doubt that the NFAs have propelled organic solar cell technology to the efficiencies necessary for a viable commercial technology–but how far can they be pushed, and will they also deliver on equally important metrics such as stability?

The underlying mechanism of 1, 8‐diiodooctane in morphology evolution is unveiled in bulk heterojunction and pseudoplanar heterojunction (PPHJ) organic solar cells (OSCs). A high‐performance PPHJ OSC is achieved by elaborately regulating the PPHJ morphology with a more balanced crystallinity factor. These results offer a deep insight into morphology regulation, which can guide the optimization of device performance.

Abstract

Additives treatment is as a very effective strategy to optimize bulk heterojunction (BHJ) morphology. However, the inherent working mechanism of this strategy still lacks systematical investigations in non‐fullerene‐acceptors‐based organic solar cells (OSCs). Herein, a series of BHJ and pseudo‐planar heterojunction (PPHJ) OSCs using PM6 and IT‐4F as the electron donor/acceptor pair, are developed to unveil the promoting effect of solvent additive 1, 8‐diiodooctane (DIO) on active layer morphologies and device performance. The study clearly demonstrates that DIO can increase the crystallinity of IT‐4F significantly, while it has less impact on PM6. It is notable that a new efficiency‐determining crystalline balanced factor (CCL_polymer/CCL_acceptor) is put forward, indicating that the more balanced CCL_polymer/CCL_acceptor results in more balanced charge mobility and much better short‐circuit current densities (J _sc) and fill factors (FF) of OSCs. The PPHJ blend film of PM6/IT‐4F(DIO) exhibits enhanced crystallinity with more balanced CCL and favorable hierarchical distribution morphology, contributing to a champion efficiency of 13.70% with a record J _sc of 20.98 mA cm⁻² and a remarkable FF of 75.9%. This work not only reveals the underlying mechanism of DIO caused morphology evolution, but also achieves highly efficient PPHJ OSCs with superior thermal stability by elaborately controlling the morphology of PPHJ film.

Organic solar cells (OSCs) outperform other technologies at low‐light intensities providing an exciting opportunity for commercialization. Previous OSC low‐light studies utilize non‐scalable materials or methods unsuitable for commercialization. Scalable materials are used to highlight the current performance of commercially relevant low‐light OSCs. The effect of parasitic resistance and a light‐soaking effect that is critical for low‐light performance are also investigated.

Abstract

Low‐light applications provide an exciting market opportunity for organic solar cells (OSCs). However, so far, studies have only considered OSCs of limited commercial viability. Herein, the applicability of a fully‐scalable, flexible, inverted non‐fullerene acceptor (NFA) containing OSC is demonstrated by showing its superior performance to silicon under low‐light, achieving 40 µW cm⁻² maximum power output at 1300 lx illumination. The effect of parasitic resistance and dark current on low‐light performance are identified. Furthermore, an atmosphere sensitive light‐soaking (LS) effect, critical for low‐light performance and resulting in undesirable S‐shaped current‐voltage characteristics, is analyzed. By employing different interlayers and photoactive layers (PALs) the origin of this LS effect is identified as poor electron extraction at the electron transport layer (ETL)/PAL interface when the common ETL ZnO is used. Two strategies are implemented to overcome the LS effect: replacement of ZnO with SnO₂ nanoparticles to reduce ETL sub‐gap electron trap states or tuning the NFA energy levels to optimize interfacial energetics. Finally, the commercial viability of these LS‐free devices is demonstrated by fabricating fully printed large‐area modules (21.6 cm²) achieving a maximum power output of 17.2 µW cm⁻², providing the most relevant example of the currently obtainable performance in commercial low‐light OSCs.

Paper‐based fully roll‐to‐roll manufactured flexible lightweight large‐area piezoelectric transducers are presented. Embedding the printed electronic layers into conventional paper webs by inline lamination and inline poling leads to piezoelectric devices with high remnant polarization and high production yield. The development gives the opportunity i.a. for novel surround sound installations of several meter length.

Abstract

The trend to a world with ubiquitous electronics has the need for novel concepts for sensors and actuators that are lightweight, flexible, low‐cost, and also sustainable. Piezoelectric transducers on the basis of functional polymers can meet these expectations. In this work, a novel concept for paper‐embedded large‐area piezoelectric devices realized solely by means of roll‐to‐roll (R2R) mass printing and post printing technologies including inline poling are introduced. The device set‐up, as well as the process technology, offers the great opportunity for a cost‐efficient and environmentally friendly mass production of thin and flexible organic large‐area piezoelectric devices. As the functional layers are embedded into paper by the hot lamination of two poly(vinylidene fluoride‐co‐trifluoroethylene) P(VDF‐TrFE) layers, the printed electronics is protected and invisible. The paper gives insights to the R2R printing of a 500 m long web including R2R post printing processes and electrical and acoustic inline characterization. Fully R2R processed devices show a high remnant polarization of up to 78 mC m⁻² and can be realized with high yield of >90%. Finally, a 360° surround‐sound installation realized with a 387 cm long paper web consisting of 56 piezoelectric speakers including wiring is presented.

Publication date: April 2021

Source: Nano Energy, Volume 82

Author(s): Tongtong Li, Shuangjie Wang, Jiabao Yang, Xingyu Pu, Bingyu Gao, Ziwei He, Qi Cao, Jian Han, Xuanhua Li

Publication date: April 2021

Source: Nano Energy, Volume 82

Author(s): Jiabao Yang, Qi Cao, Ziwei He, Xingyu Pu, Tongtong Li, Bingyu Gao, Xuanhua Li

The electronic nature of Sb‐ and Bi‐doped lead halide perovskites is an area of current scientific debate. Model compounds featuring [PbE₂I₁₆]⁸⁻ (E=Sb, Bi) anions that represent precise cut‐outs of doped perovskites are presented. The compounds display surprisingly low band gaps owing to an excellent electronic match between PbI₆ and EI₆ units and represent the first members of a promising new class of metal halide materials.

Abstract

Doping and alloying are valuable tools for modifying and enhancing the properties and performance of lead halide perovskites. However, the effects of heterovalent doping with Sb³⁺ and Bi³⁺ cations are still a matter of current investigation. Due to the different charge of the dopants compared to the constituting Pb²⁺ ions, a simultaneous creation of defects is unavoidable and the influence of these defects and the actual metal substitution become entangled. Herein, we present the first 14–15 iodido metalates, (BED)₄PbE₂I₁₆ (BED=N‐benzylethylenediammonium; E=Sb (1), Bi (2)), which are model compounds for doped lead iodide perovskites and display surprisingly low band gaps of 2.01 (1) and 1.88 eV (2). Quantum chemical investigations show that this stems from a good electronic match between the PbI₆ and EI₆ units of the compounds. Our results provide a model system for doped perovskites, but also represent the first examples of a promising new class of metal halide materials.