Junction studies on electrochemically fabricated p-n Cu(2)O homojunction solar cells for efficiency enhancement

p-n Cu(2)O homojunction solar cells were electrochemically fabricated by consecutively depositing an n-Cu(2)O layer on a p-Cu(2)O layer. In order to better understand the Fermi levels of the electrochemically grown polycrystalline p- and n-Cu(2)O layers and maximize the overall cell performance, the back and front contacts of the Cu(2)O homojunction cells were systematically changed and the I-V characteristics of the resulting cells were examined. The result shows that the intrinsic doping levels of the electrochemically prepared p-Cu(2)O and n-Cu(2)O layers are very low and they made almost Ohmic junctions with Cu metal with which previously studied p-Cu(2)O layers prepared by thermal oxidation of Cu foils are known to form Schottky junctions. The best cell performance (an η of 1.06%, a V(OC) of 0.621 V, an I(SC) of 4.07 mA cm(-2), and a fill factor (ff) of 42%) was obtained when the p-Cu(2)O layer was deposited on a commercially available ITO substrate as the back contact and a sputter deposited ITO layer was used as the front contact on the n-Cu(2)O layer. The unique features of the p-n Cu(2)O homojunction solar cell are discussed in comparison with other Cu(2)O-based heterojunction solar cells.     

A strategic review on processing routes towards scalable fabrication of perovskite solar cells

Perovskite solar cells have reached a power-conversion efficiency(PCE) of 25.6%,showing great potential with reliable moisture and heat stability.Most results are achieved on small-area devices,using conventional thin-film processing technologies like spin-coating method.However,such approaches may not be upscaled for large-area substrates.Thus,strategies and materials need to be developed for manufacturing processing routes to realize future commercial photovoltaic fabrications.Notable results have been achieved on large-area perovskite solar cells.In this review,similarities and differences of large-area perovskite fabrication mechanisms between the various pathways are investigated,especially on the parameters affecting the nucleation and crystal growth kinetics.Moreover,the methods for large-area transporting layers and electrodes are discussed,and some key issues from cells to modules.Challenges and opportunities are proposed to pave the way of high-efficiency perovskite solar modules.     

Silicon nanowire radial p-n junction solar cells

We have demonstrated a low-temperature wafer-scale etching and thin film deposition method for fabricating silicon n-p core-shell nanowire solar cells. Our devices showed efficiencies up to nearly 0.5%, limited primarily by interfacial recombination and high series resistance. Surface passivation and contact optimization will be critical to improve device performance in the future.     

Polymer strategies in perovskite solar cells

Since their emergence in 2013, perovskite solar cells have reached remarkable efficiencies exceeding 22%. Such rapid development of this technology has been possible, in part, due to the feed of ideas from previous research in organic photovoltaics (OPVs) and light emitting diodes (OLEDs). This comprehensive review discusses the various polymer strategies that have led to the success of perovskite devices: from hole and electron transporting materials to polymer templating agents. This review further covers how these strategies potentially serve to overcome the two major obstacles that stand in the way of global implementation of perovskite solar cells; stability and J‐V curve hysteresis. Through reference and comparison of OPV, OLED, and perovskite technologies, we highlight the need for a unified approach to establish appropriate control systems and ageing protocols that are necessary to further research in this exciting direction. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 549–568     

Advances in perovskite quantum-dot solar cells

Perovskite quantum-dots (PQDs) have emerged as prominent candidates for intriguing photovoltaic application due to their superior optoelectronic properties such as multiple exciton generation, bandgap tunability, electronic and surface chemistry properties, as well as flexible composition [1–5].     

A new binaphthol based hole-transporting materials for perovskite solar cells

A novel hole-transporting material (Q221) is synthesized by introducing benzyl groups onto the 1,1′-bi-2-naphthol central core as edge chains and bis(4-methoxyphenyl)amine-substituted 9H-carbazole as donor groups. A reference molecule (Q222) is prepared with hexyl edge chains. The introduction of edge chains influences their molecular orbital energy levels. Q221-based CH₃NH₃PbI₃ perovskite solar cells with carbon counter electrode exhibit the highest power conversion efficiency of 10.37% at a low doping level of Li-TFSI/TBP (15 mM/100 mM), and that of Q222-based cells is 8.87%. Q221-based cells doping with Li-TFSI/TBP of 15 mM/100 mM shows much better photovoltaic parameters compared to those doping with Li-TFSI/TBP of 30 mM/200 mM, when aged in ambient air of 30% RH without encapsulation. The new binaphthol based hole-transporting materials shows a great potential in fabricating effective perovskite solar cells.     

Fast-growing procedure for perovskite films in planar heterojunction perovskite solar cells

A fast-growing procedure (FGP) to fabricate perovskite films with large grain sizes is described in this article. In the FGP method, the perovskite precursor solution is coated onto the substrates at a temperature of ~240 ℃. The solvent in the precursor solution evaporates quickly in about 2 s, resulting in the rapid formation of a perovskite film without further annealing process. Millimeter-scale perovskite grain clusters are obtained in the film. Based on such perovskite films, fabricated planar heterojunction perovskite solar cells give a power conversion efficiency (PCE) above 8%.     

Molecular ferroelectrics for efficient perovskite solar cells

During the past decade,the power conversion efficiencies(PCEs)of organic-inorganic hybrid perovskite solar cells(PSCs)have exceeded 25%[1],which is expected to be one of the candidates for the next generation of thin-film photovoltaic technology.Fundamentally speaking,the performance of PSCs mainly depends on the light absorption capacity,defect passivation and photo-induced exciton separation and extraction of perovskite films.Under the light illumination,photo-induced excitons were separated and extracted by the built-in electric field of PSCs.     

Intermediates transformation for efficient perovskite solar cells

Perovskite materials have made a great progress in terms of the power conversion efficiency(PCE), rising from 3.8% to 25.2%. To obtain pinhole-free, superior crystal, and high-quality perovskite films with less defect, intermediates transformation is important, which has been clearly studied and widely applied.In this review, we systematically summarize the commonly formed intermediates and detailedly analyze their mechanisms from five aspects:(1) Solvent-induced intermediate;(2) HI-induced intermediate;(3)CH3NH2-induced intermediate;(4) MAAc-induced intermediate;(5) other intermediates. Finally, we also provide some prospects on high-quality perovskite fabrication based on using intermediates prudently.     

Recent progress in electron transport bilayer for efficient and low-cost perovskite solar cells: a review

Journal of Solid State Electrochemistry - Today, organic–inorganic perovskite hybrid solar cells are especially attracted by the energy industries to design and develop new-generation...     

A repeated interdiffusion method for efficient planar formamidinium perovskite solar cells

A repeated interdiffusion method is described for phase-stable and high-quality(FA,MA)PbI_3 film. The crystallization and growth of the perovskite films can be well controlled by adjusting the reactant concentrations.With this method, dense, smooth perovskite films with large crystals have been obtained. Finally, a PCE of 16.5% as well as a steady-state efficiency of 16.3% is achieved in the planar perovskite solar cell.     

Two-dimensional perovskite capping layer for stable and efficient tin-lead perovskite solar cells

Mixed tin-lead iodide perovskites exhibit the characteristics of low toxicity and improved light harvesting ability up to nearinfrared(NIR) spectral region, making them as an attractive alternative for traditional lead based perovskites. However, the performance of lead-based perovskites solar cells is still far inferior to their lead analogues owing to the unavoidable oxidation of Sn~(2+)to Sn~(4+). Here we introduced two-dimensional(2D) perovskite on the top of three dimensional(3D) perovskite film as a capping layer to reduce the self-oxidation, and thus improved the device stability. 2D capping layer was then confirmed by X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS) analysis. The existence of the 2D protecting thin layer significantly reduce the spontaneous Sn~(2+)oxidation, thus improve the device performance and reduce the hysteresis. The phenomena could be ascribed to the improved charge extraction efficiency causing by prohibited nonradiative recombination. On top of this, the photovoltaic devices based on conventional-structure configuration were fabricated. Taking advantage of the 2D capping layer, 2D/3D hybrid perovskite photovoltaic devices achieve a open-circuit voltage(Voc) of 0.77 V with short circuit current density(Jsc) of 26.60 mA cm~(-2), delivering the best-performing power conversion efficiency of 15.5%. Moreover, the 2D/3D perovskite devices maintained 60% its initial efficiency after 40 h exposed in air(humidity around 30%, temperature 22 °C),while 3D perovskite-based devices completely failed.     

Research activities on perovskite solar cells in China

Perovskite solar cells(PSCs) have attracted much attention because of their high efficiencies and low costs for production.Although academic research started late in China, compared to that in Europe and Korea, the majority of active PSC research is now conducted in China; furthermore, Chinese research groups currently hold the certified highest efficiency record for both an individual PSC and a PSC module. China is also the world's largest supplier of solar modules, making it a promising country in which to realize the commercialization of PSCs. Herein, we review PSC research activities undertaken in China(both academic and industrial) and discuss significant remaining challenges to overcome for early commercialization of PSCs. We propose that research activities shift away from material and device structure development toward improving PSC stability and developing methods for large-area module fabrication. In addition, we suggest that a recognized certification center is urgently needed in China to further accelerate PSC research.     

Nickel oxide for inverted structure perovskite solar cells

The emergence of inverted perovskite solar cells(PSCs) has attached great attention derived from the potential in improving stability. Charge transporting layer, especially hole transporting layer is crucial for efficient inverted PSCs. Organic materials were used as hole transporting layer previously. Recently, more and more inorganic hole transporting materials have been deployed for further improving the device stability. Nickel oxide(NiOx) as p-type metal oxide, owning high charge mobility and intrinsic stability,has been widely adopted in inverted PSCs. High performance over 20% efficiency has been achieved on NiOx base inverted PSCs. Herein, we have summarized recent progresses and strategies on the NiOx based PSCs, including the synthesis or deposition methods of NiOx, doping and surface modification of NiOx for efficient and stable PSCs. Finally, we will discuss current challenges of utilizing NiOx HTLs in PSCs and attempt to give probable solutions to make further development in efficient as well as stable NiOx based PSCs.     

钙钛矿太阳能电池的商业化进展与挑战

钙钛矿太阳电池是一项颠覆性的光伏技术,具有能量转化效率高、生产成本低、制备工艺简单等优势。当前,钙钛矿太阳能电池的认证效率已达25.7%,但其面临着严重的商业化瓶颈,如稳定性差、模组效率相对低、铅毒性等,且这些问题相互关联。本文简述了钙钛矿太阳能电池的工作原理和器件结构,并归纳总结了在解决钙钛矿太阳能电池稳定性、封装和模组化等商业化瓶颈问题方面的主要研究进展。最后,本文提出了钙钛矿光伏商业化进程中值得关注的解决措施。     

Additive engineering for stable halide perovskite solar cells

Halide perovskite solar cells(PSCs)have already demonstrated power conversion efficiencies above 25％,which makes them one of the most attractive photovoltaic te...     

Recent advances in high-performance semitransparent perovskite solar cells

Semitransparent perovskite photovoltaics have been developed to realize practical applications, such as windows in buildings/automobiles or the top cells of tandem devices. Among the functional layers constituting solar cell devices, fabricating efficient semitransparent light absorbers is one of the key issues for developing semitransparent devices. This short review describes the recent strategies for structuring semitransparent perovskite layers to achieve high performance in terms of both power conversion efficiency and transmittance.     

Fullerenes with dipoles: boosting the efficiency of perovskite solar cells

An unfortunate and fortunate discovery is that metal halide perovskites are not completely defect tolerant,while fullerenes,which are inexpensive and broadly applied in organic solar cells,have a considerable passivation effect toward the surface defects of perovskite materials[1].The improvement of perovskite efficiency and stability in the last five years has shown the importance of passivating interfacial charge traps to reduce charge carrier recombination and to slow down the degradation of perovskites[2].     

Organs on microfluidic chips: A mini review

Microfluidic technology provides opportunities to create in vitro models with physiological microenvironment for cell study. Introducing the identified key aspects, including tissue-tissue interfaces, spatiotemporal chemical gradients, and dynamic mechanical forces, of living organs into the microfluidic system, “organs-on-chips” display an unprecedented application potential in a lot of biological fields such as fundamental physiological and pathophysiological research, drug efficacy and toxicity testing, and clinical diagnosis. Here, we review the recent development of organs-on-chips and briefly discuss their future challenges.