The photovoltaics of organic–inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regardi...

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects

The bulk-heterojunction blend of an electron donor and an electron acceptor material is the key component in a solution-processed organic photovoltaic device. In the past decades, a p-type conjugated polymer and an n-type fullerene derivative have been the most commonly used electron donor and electron acceptor, respectively. While most advances of the device performance come from the design of new polymer donors, fullerene derivatives have almost been exclusively used as electron acceptors in organic photovoltaics. Recently, nonfullerene acceptor materials, particularly small molecules and oligomers, have emerged as a promising alternative to replace fullerene derivatives. Compared to fullerenes, these new acceptors are generally synthesized from diversified, low-cost routes based on building block materials with extraordinary chemical, thermal, and photostability. The facile functionalization of these molecules affords excellent tunability to their optoelectronic and electrochemical properties. Within t...

Nonfullerene Acceptor Molecules for Bulk Heterojunction Organic Solar Cells

Textiles have been concomitant of human civilization for thousands of years. With the advances in chemistry and materials, integrating textiles with energy harvesters will provide a sustainable, environmentally friendly, pervasive, and wearable energy solution for distributed on-body electronics in the era of Internet of Things. This article comprehensively and thoughtfully reviews research activities regarding the utilization of smart textiles for harvesting energy from renewable energy sources on the human body and its surroundings. Specifically, we start with a brief introduction to contextualize the significance of smart textiles in light of the emerging energy crisis, environmental pollution, and public health. Next, we systematically review smart textiles according to their abilities to harvest biomechanical energy, body heat energy, biochemical energy, solar energy as well as hybrid forms of energy. Finally, we provide a critical analysis of smart textiles and insights into remaining challenges and future directions. With worldwide efforts, innovations in chemistry and materials elaborated in this review will push forward the frontiers of smart textiles, which will soon revolutionize our lives in the era of Internet of Things.

Smart Textiles for Electricity Generation.

All-polymer solar cells (all-PSCs) consisting of polymer donors (PDs) and polymer acceptors (PAs) have drawn tremendous research interest in recent years. It is due to not only their tunable optical, electrochemical, and structural properties, but also many superior features that are not readily available in conventional polymer-fullerene solar cells (fullerene-PSCs) including long-term stability, synthetic accessibility, and excellent film-forming properties suitable for large-scale manufacturing. Recent breakthroughs in material design and device engineering have driven the power conversion efficiencies (PCEs) of all-PSCs exceeding 11%, which is comparable to the performance of fullerene-PSCs. Furthermore, outstanding mechanical durability and stretchability have been reported for all-PSCs, which make them stand out from the other small molecule-based PSCs as a promising power supplier for wearable electronic devices. This review provides a comprehensive overview of the important work in all-PSCs, in which pertinent examples are deliberately chosen. First, we describe the key components that enabled the recent progresses of all-PSCs including rational design rules for efficient PDs and PAs, blend morphology control, and light harvesting engineering. We also review the recent work on the understanding of the stability of all-PSCs under various external conditions, which highlights the importance of all-PSCs for future implementation and commercialization. Finally, because all-PSCs have not yet achieved their full potential and are still undergoing rapid development, we offer our views on the current challenges and future prospects.

Recent Advances, Design Guidelines, and Prospects of All-Polymer Solar Cells.

All-inorganic perovskite solar cells with high efficiency and improved stability are promising for commercialization. A multistep solution-processing method was developed to fabricate high-purity inorganic CsPbBr3 perovskite films for use in efficient solar cells. By tuning the number of deposition cycles (n) of a CsBr solution, the phase conversion from CsPb2 Br5 (n ≤3), to CsPbBr3 (n=4), and Cs4 PbBr6 (n≥5) was optimized to achieve vertical- and monolayer-aligned grains. Upon interfacial modification with graphene quantum dots, the all-inorganic perovskite solar cell (without a hole-transporting layer) achieved a power conversion efficiency (PCE) as high as 9.72 % under standard solar illumination conditions. Under challenging conditions, such as 90 % relative humidity (RH) at 25 °C or 80 °C at zero humidity, the optimized device retained 87 % PCE over 130 days or 95 % over 40 days, compared to the initial efficiency.

High-Purity Inorganic Perovskite Films for Solar Cells with 9.72 % Efficiency.

Thermally Stable All-Polymer Solar Cells with High Tolerance on Blend Ratios

A Universal Strategy to Utilize Polymeric Semiconductors for Perovskite Solar Cells with Enhanced Efficiency and Longevity

In this work, we demonstrate high-efficiency planar perovskite solar cells (PSCs), using room-temperature sputtered niobium oxide (Nb2O5) as the electron-transporting layer (ETL). Widely spread ETL-like TiO2 often requires high-temperature (>450 °C) sintering, which is not desired for the fabrication of flexible devices. The amorphous Nb2O5 (labeled as a-Nb2O5) ETL, without any heat treatment, can give a best power conversion efficiency (PCE) of 17.1% for planar PSCs. Interestingly, the crystalline Nb2O5 (labeled as c-Nb2O5), with high-temperature (500 °C) annealing, results in a very similar PCE of 17.2%, indicating the great advantage of a-Nb2O5 in energy saving. We thus carried out a systematical investigation on the properties of the a-Nb2O5 film. The Hall effect measurements indicate both high mobility and conductivity of the a-Nb2O5 film. Kelvin probe force microscopy measurements define the Fermi levels of a-Nb2O5 and c-Nb2O5 as −4.31 and −4.02 eV, respectively, which allow efficient electron extra...

Room-Temperature Processed Nb2O5 as the Electron-Transporting Layer for Efficient Planar Perovskite Solar Cells

All-polymer organic solar cells offer exceptional stability. Unfortunately, the use of bulk heterojunction (BHJ) structure has the intrinsic challenge to control the side-chain entanglement and bac...

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Simultaneously Improved Efficiency and Stability in All-Polymer Solar Cells by a P-i-N Architecture

Metal halide perovskite quantum dots (Pe-QDs) are of great interest in new-generation photovoltaics (PVs). However, it remains challenging in the construction of conductive and intact Pe-QD films to maximize their functionality. Herein, a ligand-assisted surface matrix strategy to engineer the surface and packing states of Pe-QD solids is demonstrated by a mild thermal annealing treatment after ligand exchange processing (referred to as "LE-TA") triggered by guanidinium thiocyanate. The "LE-TA" method induces the formation of surface matrix on CsPbI3 QDs, which is dominated by the cationic guanidinium (GA+ ) rather than the SCN- , maintaining the intact cubic structure and facilitating interparticle electrical interaction of QD solids. Consequently, the GA-matrix-confined CsPbI3 QDs exhibit remarkably enhanced charge mobility and carrier diffusion length compared to control ones, leading to a champion power conversion efficiency of 15.21% when assembled in PVs, which is one of the highest among all Pe-QD solar cells. Additionally, the "LE-TA" method shows similar effects when applied to other Pe-QD PV systems like CsPbBr3 and FAPbI3 (FA = formamidinium), indicating its versatility in regulating the surfaces of various Pe-QDs. This work may afford new guidelines to construct electrically conductive and structurally intact Pe-QD solids for efficient optoelectronic devices.

Yannan Zhang

Papers

Thermally Stable All-Polymer Solar Cells with High Tolerance on Blend Ratios

A Universal Strategy to Utilize Polymeric Semiconductors for Perovskite Solar Cells with Enhanced Efficiency and Longevity

Room-Temperature Processed Nb2O5 as the Electron-Transporting Layer for Efficient Planar Perovskite Solar Cells

Simultaneously Improved Efficiency and Stability in All-Polymer Solar Cells by a P-i-N Architecture

Guanidinium-Assisted Surface Matrix Engineering for Highly Efficient Perovskite Quantum Dot Photovoltaics.