Improved charge extraction and wide spectral absorption promote power conversion efficiency of perovskite solar cells (PSCs). The state‐of‐the‐art carbon‐based CsPbBr3 PSCs have an inferior power ...output capacity because of the large optical band gap of the perovskite film and the high energy barrier at perovskite/carbon interface. Herein, we use alkyl‐chain regulated quantum dots as hole‐conductors to reduce charge recombination. By precisely controlling alkyl‐chain length of ligands, a balance between the surface dipole induced charge coulomb repulsive force and quantum tunneling distance is achieved to maximize charge extraction. A fluorescent carbon electrode is used as a cathode to harvest the unabsorbed incident light and to emit fluorescent light at 516 nm for re‐absorption by the perovskite film. The optimized PSC free of encapsulation achieves a maximum power conversion efficiency up to 10.85 % with nearly unchanged photovoltaic performances under 80 %RH, 80 °C, or light irradiation in air.
Chain gang: Regulating the alkyl‐chain length of quantum dots attached to inorganic CsPbBr3 perovskites maximizes charge extraction and transfer at the perovskite/carbon interface. The optimized inorganic CsPbBr3 perovskite solar cell (PSC) with C12 alkyl chain QDs yields an efficiency of up to 10.85 %.
The all‐inorganic CsPbBr3 perovskite solar cell (PSC) is a promising solution to balance the high efficiency and poor stability of state‐of‐the‐art organic–inorganic PSCs. Setting inorganic ...hole‐transporting layers at the perovskite/electrode interface decreases charge carrier recombination without sacrificing superiority in air. Now, M‐substituted, p‐type inorganic Cu(Cr,M)O2 (M=Ba2+, Ca2+, or Ni2+) nanocrystals with enhanced hole‐transporting characteristics by increasing interstitial oxygen effectively extract holes from perovskite. The all‐inorganic CsPbBr3 PSC with a device structure of FTO/c‐TiO2/m‐TiO2/CsPbBr3/Cu(Cr,M)O2/carbon achieves an efficiency up to 10.18 % and it increases to 10.79 % by doping Sm3+ ions into perovskite halide, which is much higher than 7.39 % for the hole‐free device. The unencapsulated Cu(Cr,Ba)O2‐based PSC presents a remarkable stability in air in either 80 % humidity over 60 days or 80 °C conditions over 40 days or light illumination for 7 days.
Cu(Cr,M)O2 nanocrystals with hole boosting by increasing the amount of interstitial oxygen enables them to be promising HTMs for all‐inorganic CsPbBr3 perovskite solar cells. The optimized device with Cu(Cr,Ba)O2 achieves a record efficiency as high as 10.79 %.
In the last decade, organic–inorganic hybrid lead-halide perovskites have been attracted tremendous attentions in the photovoltaic and optoelectronic community. Especially for perovskite solar cells ...(PSCs), the certified efficiency is up to as high as 25.5%, which has surpassed polycrystalline silicon solar cells and is comparable to the monocrystalline silicon solar cells. Till now, although the chemical instability of perovskite has been well alleviated by optimizing the lattice structure, the detrimental lead element is still a challenge for the commercialization process of PSC devices. To effectively resolve this issue, lead-free halide perovskites (LFHPs) have gained growing attentions recently due to their theoretically excellent optoelectronic properties and eco-friendly feature. With the aim to promote the development of LFHPs, in this review, we have mainly summarized the recent advancement of various LFHP materials and their applications in photovoltaics, light-emitting diodes (LEDs), photodetectors and other devices. Strategies for stabilization of perovskite lattice and performance improvement of optoelectronic devices including fabrication technology, compositional engineering and interfacial optimization are also emphasized. Finally, the potential and challenges of LFHPs are further discussed, providing new research direction for future development.
Display omitted
•This review covers the hot top of Pb-free perovskites for optoelectronic devices.•Different elements can be employed to replace lead atoms in perovskite lattice.•Strategies for improving the performance and stability are summarized.•A brief outlook, including the remained issues and challenge is proposed.
Moisture is the worst enemy for state‐of‐the‐art perovskite solar cells (PSCs). However, the flowing water vapor within nanoporous carbonaceous materials can create potentials. Therefore, it is a ...challenge to integrate water vapor and solar energies into a single PSC device. We demonstrate herein all‐inorganic cesium lead bromide (CsPbBr3) solar cells tailored with carbon electrodes to simultaneously harvest solar and water‐vapor energy. Upon interfacial modification and plasma treatment, the bifunctional PSCs yield a maximum power conversion efficiency up to 9.43 % under one sun irradiation according to photoelectric conversion principle and a power output of 0.158 μW with voltage of 0.35 V and current of 0.45 μA in 80 % relative humidity through the flowing potentials at the carbon/water interface. The initial efficiency is only reduced by 2 % on exposing the inorganic PSC with 80 % humidity over 40 days. The successful realization of physical proof‐of‐concept multi‐energy integrated solar cells provides new opportunities of maximizing overall power output.
Rising damp: An all‐inorganic perovskite solar cell backed by a tailored carbon electrode is made to simultaneously harvest solar and water‐vapor energies, in that the water vapor within nanoporous carbonaceous materials can generate potentials, yielding a maximum power conversion efficiency (PCE) of 9.43 % under one sun irradiation and a power output of 0.158 μW with a voltage of 0.35 V and a current of 0.45 μA in 80 % relative humidity.
Interfacial charge recombination seriously drags efficiency enhancement of all-inorganic perovskite solar cells (PSCs) because of large energy-level differences. Although CsPbBr3-xIx light-harvesters ...markedly reduce interfacial charge recombination, the long-term stability of solar cell devices is still unsatisfactory to meet practical requirements. Here we present the improved charge extraction by setting an intermediated energy-level at CsPbBr3/carbon interface with colorful CsSnBr3-xIx quantum dots (QDs). The charge extraction is maximized by tuning Br:I ratio, yielding a power conversion efficiency as high as 9.13% for CsSnBr2I QDs-tailored CsPbBr3 solar cell. Moreover, all the devices show high stability in 80%RH or 80 °C over 720 h. The interfacial decoration of all-inorganic perovskite solar cells by lead-free perovskite QDs provides new opportunities of enhancing solar cell efficiency and reducing environmental impacts.
Display omitted
•PQDs with tunable bandgaps are synthesized to modify CsPbBr3/carbon interface.•An intermediate energy level is set at CsPbBr3/carbon interface to extract holes.•The electron-hole recommendation is markedly restricted.•A maximized PCE of 9.13% is achieved for the PQDs tailored inorganic PSC.
The crystal distortion such as lattice strain and defect located at the surfaces and grain boundaries induced by soft perovskite lattice highly determines the charge extraction‐transfer dynamics and ...recombination to cause an inferior efficiency of perovskite solar cells (PSCs). Herein, the authors propose a strategy to significantly reduce the superficial lattice tensile strain by means of incorporating an inorganic 2D Cl‐terminated Ti3C2 (Ti3C2Clx) MXene into the bulk and surface of CsPbBr3 film. Arising from the strong interaction between Cl atoms in Ti3C2Clx and the under‐coordinated Pb2+ in CsPbBr3 lattice, the expanded perovskite lattice is compressed and confined to act as a lattice “tape”, in which the PbCl bond plays a role of “glue” and the 2D Ti3C2 immobilizes the lattice. Finally, the defective surface is healed and a champion efficiency as high as 11.08% with an ultrahigh open‐circuit voltage up to 1.702 V is achieved on the best all‐inorganic CsPbBr3 PSC, which is so far the highest efficiency record for this kind of PSCs. Furthermore, the unencapsulated device demonstrates nearly unchanged performance under 80% relative humidity over 100 days and 85 °C over 30 days.
Arising from the formation of strong PbCl bonding, chlorine terminated Ti3C2Clx MXenes are used as lattice “tape” to reduce the defects and release tensile strain located at interfaces and grain boundaries of CsPbBr3 perovskite film, achieving a champion efficiency up to 11.08% with an ultrahigh voltage of 1.702 V for CsPbBr3 perovskite solar cells.
All‐inorganic CsPbX3 (X=I, Br) perovskite solar cells are regarded as cost‐effective and stable alternatives for next‐generation photovoltaics. However, sluggish charge extraction at ...CsPbX3/charge‐transporting material interfaces, which arises from large interfacial energy differences, have markedly limited the further enhancement of solar cell performance. In this work, the work function (WF) of the back electrode is tuned by doping alloyed PtNi nanowires in carbon ink to promote hole extraction from CsPbBr3 halides, while an intermediate energy by setting carbon quantum dots (CQDs) at TiO2/CsPbBr3 interface bridges electron transportation. The preliminary results demonstrate that the matching WFs and intermediate energy level markedly reduce charge recombination. A power conversion efficiency of 7.17 % is achieved for the WF‐tuned all‐inorganic perovskite solar cell, in comparison with 6.10 % for the pristine device, and this is further increased to 7.86 % by simultaneously modifying with CQDs. The high efficiency and improved stability make WF‐controlled all‐inorganic perovskite solar cells promising to develop advanced photovoltaic platforms.
Back under alloyed control: In all‐inorganic perovskite solar cells, the work function (WF) of the back electrode is tuned by incorporating PtNi nanowires into state‐of‐the‐art carbon paste to reduce the energy difference at the CsPbBr3/carbon interface. The matching WFs of the back electrode and the intermediate energy level at the TiO2/CsPbBr3 interface markedly promote charge extraction.
The crystal structure of cesium lead halide (CsPbX3, X = I, Br, Cl) determines its charge‐carrier trap state and solar‐to‐electrical conversion ability in inorganic perovskite solar cells (PSCs). ...Here, the compositional engineering of inorganic CsPbBr3 perovskite by means of doping with various alkali metal cations is studied. The lattice dimensions and energy levels of Cs1‐xRxPbBr3 (R = Li, Na, K, Rb, x = 0–1) halides are optimized by tuning Cs/R ratio. Arising from promoting effects of alkali metal cations doped perovskite halides such as lattice shrink, crystallized dynamics, and electrical‐energy distribution, a maximum power conversion efficiency as high as 9.86% is achieved for hole transporting layer‐free Cs0.91Rb0.09PbBr3 tailored solar cell owing to the suppressed non‐radiative losses and radiative recombination. Furthermore, the all‐inorganic Cs0.91Rb0.09PbBr3 solar cell without encapsulation remains 97% of initial efficiency when suffering persistent attack by 80% RH in air atmosphere over 700 h, which is in comparable with state‐of‐the‐art organic–inorganic hybrid and all‐inorganic PSC devices. Employing alkali metal cations to modulate perovskite layers provide new opportunities of making high‐performance inorganic PSC platforms.
The lattice of inorganic CsPbBr3 halide is modulated by doping alkali metal cations to form Cs1−xRxPbBr3 (R = Li, Na, K, Rb, x = 0–1) perovskites. Through tuning R/Cs ratio, a PCE up to 9.86% and improved stability in 80% humidity are achieved for HTL‐free Cs0.91Rb0.09PbBr3 solar cell.
It is a challenge to harvest ocean wave energy by electrokinetic principle. We present here film-type generators made of carbon for wave energy harvest. The electrical signals arise from charge ...transportation along percolating channels driven by moving electric double-layer boundary at generator/seawater interfaces. Both voltage and current outputs are maximized by optimizing carbon dosage, wave frequency, hoisting angle and seawater temperature, producing a voltage of > 20 mV and a current of > 10 microamp from a 15 cm2-sized generator. We illustrate the electricity can be scaled up through series and parallel connections of multiple generators. Upon persistently rushing by waves, these film-type generators are stable over several hours. This approach to ocean wave energy harvest provides new opportunities for unprecedented low-investment, scalable power outputs and high stability.
Display omitted
•Ocean wave energy is harvested by film-type generators.•The generators harvest wave energy through electrokinetic principle.•A voltage of > 20 mV and a current of > 10 μA are produced in a 15 cm2-sized generator.•These generators are sustainably stable upon persistent attack by waving ocean.•The generators are economic for ocean wave energy harvest.
All-inorganic CsPbBr
3
perovskite solar cells (PSCs) are promising candidates to balance the stability and efficiency issues of organic-inorganic hybrid devices. However, the large energy barrier for ...charge transfer and narrow spectral response are still two challenging problems for performance improvement. We present here an organic bulk-heterojunction {poly(3-hexylthiophene-2,5-diyl):6,6-phenyl C61 butyric acid methyl ester (P3HT: PCBM)} photoactive layer to boost the charge extraction and to widen the spectral absorption, achieving an enhanced power conversion efficiency up to 8.94% by optimizing the thickness of P3HT: PCBM photoactive layer, which is much higher than 6.28% for the pristine CsPbBr
3
device. The interaction between the carbonyl group in PCBM and unsaturated Pb atom in the perovskite surface can effectively passivate the defects and reduce charge recombination. Furthermore, the coupling effect between PCBM and P3HT widens the spectral response from 540 to 650 nm for an increased short-circuit current density. More importantly, the devices are relatively stable over 75 days upon persistent attack by 70% relative humidity in air condition. These advantages of high efficiency, excellent long-term stability, cost-effectiveness and scalability may promote the commercialization of inorganic PSCs.
PDF
