新型太阳能汽车的探索与思考

本文从太阳能电池的转化效率、储能器件的性能比较等方面,论述了制约太阳能汽车发展的瓶颈因素;分析研究了锂电池和飞轮电池的优缺点,提出了锂电池太阳能汽车和太阳能飞轮电池汽车的结构模型。

新型太阳能汽车的探索与思考

本文从太阳能电池的转化效率、储能器件的性能比较等方面,论述了制约太阳能汽车发展的瓶颈因素;分析研究了锂电池和飞轮电池的优缺点,提出了锂电池太阳能汽车和太阳能飞轮电池汽车的结构模型。

江苏亚热带低山丘陵区农田生态系统能量流及其调控途径

能量指标是评价农田生态系统生产力和效益的重要参考,因为作物生产本身是转化太阳能为人类和其他动物可能利用的化学潜能的过程。人类虽不能控制太阳辐射能输入地面的数量,但辅助能量的输入,诸如肥料、耕作、灌排和防治病虫害等。

不同频次刈割对内蒙古羊草草原群落能量固定与分配规律的影响

对内蒙古羊草草原在不同频次刈割影响下群落能量固定与分配规律的研究结果显示,群落地上能量现存量与刈割频次呈显著负相关关系,地下0～30cm根系的能量现存量具有基本相似的变化趋势,区别在于17年内刈割3次的处理明显高于未割对照处理。群落总能量现存量的变化趋势与地下部分的变化完全一致。羊草草原地上部分的太阳能转化效率随刈割频次的增加逐渐下降,在未割对照群落中为0.257%,而1年割2次群落仅为未割对照群落的37%。群落地上部分的能量含量也随刈割频次的增加呈线性下降趋势,地下部分能量含量则没有规律性的变化。在连年刈割影响下,群落能量向根系的分配比例增加,0～10cm根系所蓄存能量在地下0～30cm根系中所占比例也有增加趋势。但这种变化与刈割频次没有线性关系。

Study of Back Contacts for CdTe Solar Cells

ZnTe/ZnTe∶Cu layer is used as a complex back contact. The parameters of CdTe solar cells with and without the complex back contacts are compared. The effects of un-doped layer thickness, doped concentration and post-deposition annealing temperature of the complex layer on solar cells performance are investigated.The results show that ZnTe/ZnTe∶Cu layer can improve back contacts and largely increase the conversion efficiency of CdTe solar cells. Un-doped layer and post-deposition annealing of high temperature can increase open voltage. Using the complex back contact, a small CdTe cell with fill factor of 73.14% and conversion efficiency of 12.93% is obtained.

High-efficiency colorful perovskite solar cells using TiO2 nanobowl arrays as a structured electron transport layer

The rapid development of perovskite solar cells(PSCs) has stimulated great interest in the fabrication of colorful PSCs to meet the needs of aesthetic purposes in varied applications including building integrated photovoltaics and wearable electronics. However, it remains challenging to prepare high-efficiency PSCs with attractive colors using perovskites with broad optical absorption and large absorption coefficients. Here we show that high-efficiency PSCs exhibiting distinct structural colors can be readily fabricated by employing Ti O2 nanobowl(NB) arrays as a nanostructured electron transport layer to integrate with a thin overlayer of perovskite on the NB arrays. A new crystalline precursor film based on lead acetate was prepared through a Lewis acid-base adduct approach, which allowed for the formation of a uniform overlayer of high-quality CH3 NH3 Pb I3 crystals on the inner walls of the NBs. The PSCs fabricated using the Ti O2 NB arrays showed angle-dependent vivid colors under light illumination. The resultant colorful PSCs exhibited a remarkable photovoltaic performance with a champion efficiency up to16.94% and an average efficiency of 15.47%, which are recordbreaking among the reported colorful PSCs.

n-Octyl substituted quinoxaline-based polymer donor enabling all-polymer solar cell with efficiency over 17%

Recently, the power conversion efficiencies(PCEs) of all-polymer solar cells(all-PSCs) have increased rapidly. To further increase the PCE of all-PSCs, it is necessary to create new donor polymers matching the polymer acceptors. In this paper, we synthesize a new quinoxaline-based polymer donor PBQ8 with n-octyl side chain on the quinoxaline unit, which possesses the same skeleton structure to the previously reported PBQ5(with isooctyl side chain). The effects of alkyl side chains on the physicochemical properties of the polymer donor were investigated. In comparison with PBQ5, PBQ8 exhibits stronger intermolecular interactions and better molecular packing. When blending with polymer acceptor PY-IT, the PBQ8:PY-IT based devices demonstrated a higher PCE value of 17.04%, which is one of the highest PCEs occurred in the all-PSCs. And the PBQ5:PY-IT(PCE 15.56%, Voc0.907 V, FF 69.72%, and Jsc24.60 m A cm^(-2)) is much lower. The PBQ8:PY-IT blend displayed more efficient exciton dissociation, better molecular stacking properties, preferable phase separation and higher mobility. These indicate that as an effective method, side chain engineering can improve the efficiency of the all-PSCs.

Intermediate phase-enhanced Ostwald ripening for the elimination of phase segregation in efficient inorganic CsPbIBr_(2)perovskite solar cells

Mixed halide perovskites with the ability to tune bandgaps exhibit attractive applications in tandem solar cells,building integrated photovoltaic and wavelength-tunable light-emitting devices.However,halide demixing under illumination or in the dark with a charge-carrier injection in both hybrid and inorganic perovskites results in bandgap instability and current-density-voltage(J-V)hysteresis,which can significantly hamper their application.Here,we demonstrate that halide segregation and J-V hysteresis in mixed halide inorganic CsPbIBr_(2)solar cells can be effectively mitigated by introducing an intermediate phase-enhanced Ostwald ripening through the control of the chemical composition in the CsPbIBr_(2)precursor solution.Excess amounts of either PbBr_(2)or CsI are incorporated into originally even molar amounts of PbBr_(2)and CsI precursor solutions.With the PbBr_(2)-excess,we observed an enlarged perovskite grain size,no detectable halide phase segregation at the grain boundaries nor the perovskite/TiO2 interface,an increased minority carrier lifetime,a reduced J-V hysteresis,and an improved solar-cell performance.However,different CsI:PbBr_(2)stoichiometric ratios were found to have different effects on the performance of the perovskite solar cell.The excessive lead phase is reactive with the dimethyl sulfoxide(DMSO)in the precursor solution to form the Pb(I,Br)2·DMSO complex and the quasi-twodimensional(2D)CsPb_(2)(I,Br)5,which are conducive to Ostwald maturation and defect extinction.Finally,the CsPbIBr_(2)solar cell with a PbBr_(2)-excess precursor composition reaches a power conversion efficiency(PCE)of 9.37%(stabilized PCE of 8.48%)and a maximum external quantum efficiency of over 90%.

Intrinsically inert hyperbranched interlayer for enhanced stability of organic solar cells

Device stability becomes one of the most crucial issues for the commercialization of organic solar cells(OSCs) after high power conversion efficiencies have been achieved. Besides the intrinsic stability of photoactive materials, the chemical/catalytic reaction between interfacial materials and photoactive materials is another critical factor that determines the stability of OSC devices. Herein, we design and synthesize a reaction-inert rylene diimide-embedded hyperbranched polymer named as PDIEIE, which effectively reduces the work function of indium tin oxide electrode from 4.62 to 3.65 eV. Meanwhile, PDIEIE shows negligible chemical reaction with high-performance photoactive materials and no catalytic effect under strong ultraviolet illumination, resulting in much better photo-stability of OSCs with PDIEIE cathode interlayer(CIL), relative to the traditional CILs, including most-widely used metal oxides and polyethyleneimine derivatives.

A novel dopant for spiro-OMeTAD towards efficient and stable perovskite solar cells

2,2’,7,7’-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9’-spirobifluorene(spiro-OMeTAD), as the most commonly used hole transport material(HTM), plays a significant role in the normal structured(n-i-p) high-efficiency perovskite solar cells(PSCs). In general, it is prepared by a halogen solvent(chlorobenzene, CBZ) and needs an ion dopant(lithium bis(trifluoromethanesulfonyl)imide, Li-TFSI) to improve its conductivity and hole mobility. However, such a halogen solvent is not environmentally friendly and the widely used LiTFSI dopant would affect the stability of PSCs. Herein, we develop a non-halogen solvent-tetrahydrofuran(THF)-prepared spiro-OMeTAD solution with a new p-type dopant,potassium bis(fluorosulfonyl)imide(K-FSI), to apply into PSCs. By this strategy, high-hole-mobility spiro-OMeTAD film is achieved. Meanwhile, the potassium ions introduced by diffusion into perovskite surface passivate the interfacial defects. Therefore, a hysteresis-free champion PSC with an efficiency of 21.02% is obtained, along with significantly improved stability against illumination and ambient conditions. This work provides a new strategy for HTMs toward hysteresis-free high-efficiency and stable PSCs by substituting dopants.

Optimizing the component ratio of PEDOT:PSS by water rinse for high efficiency organic solar cells over 16.7%

For the state-of-the-art organic solar cells(OSCs),PEDOT:PSS is the most popularly used hole transport material for the conventional structure.However,it still suffers from several disadvantages,such as low conductivity and harm to ITO due to the acidic PSS.Herein,a simple method is introduced to enhance the conductivity and remove the additional PSS by water rinsing the PEDOT:PSS films.The photovoltaic devices based on the water rinsed PEDOT:PSS present a dramatic improvement in efficiency from 15.98%to 16.75%in comparison to that of the untreated counterparts.Systematic characterization and analysis reveal that although part of the PEDOT:PSS is washed away,it still leaves a smoother film and the ratio of PEDOT to PSS is higher than before in the remaining films.It can greatly improve the conductivity and reduce the damage to substrates.This study demonstrates that finely modifying the charge transport materials to improve conductivity and reduce defeats has great potential for boosting the efficiency of OSCs.

Photovoltaic efficiency enhancement of polycrystalline silicon solar cells by a highly stable luminescent film

Si-based solar cells have dominated the entire photovoltaic market,but remain suffering from low power conversion efficiency(PCE),partly because of the poor utilization of ultraviolet(UV)light.Europium(III)(Eu^3+)complexes with organic ligands are capable of converting UV light into strong visible light,which makes them ideal light converter to increase the efficiency of solar cells.However,the low stability of such complexes seriously hampers their practical applications.In this work,we report a highly stable and luminescent ethylene-vinyl acetate(EVA)copolymer film consisting of a Eu^3+complex as a down-shift material,Eu(ND)4 CTAC(ND=4-hydroxy-2-methyl-1,5-naphthyridine-3-carbonitrile,CTAC=hexadecyl trimethyl ammonium chloride),coating of which onto the surface of large area polycrystalline silicon solar cells(active area:110 cm^2)results in an increase of PCE from 15.06%to 15.57%.Remarkable stability of the luminescent film was also demonstrated under lightsoaking test for 500 h,and no obvious luminescence degradation can be observed.The remarkable enhancement of the conversion efficiency by 0.51%absolute on such a large active area,together with the high stability of the luminescent film,demonstrates a prospect for the implementation of the films in photovoltaic industry.

A low-temperature TiO2/SnO2 electron transport layer for high-performance planar perovskite solar cells

Conventional titanium oxide(TiO2) as an electron transport layer(ETL) in hybrid organic-inorganic perovskite solar cells(PSCs) requires a sintering process at a high temperature to crystalize, which is not suitable for flexible PSCs and tandem solar cells with their low-temperatureprocessed bottom cell. Here, we introduce a low-temperature solution method to deposit a TiO2/tin oxide(SnO2) bilayer towards an efficient ETL. From the systematic measurements of optical and electronic properties, we demonstrate that the TiO2/SnO2 ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface, both of which are beneficial to photo-generated carrier separation and transport. As a result, PSCs with TiO2/SnO2 bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO2 and SnO2 single-layer ETL counterparts. The champion PSC has a power conversion efficiency(PCE) of 19.11% with an open-circuit voltage(Voc)of 1.15 V, a short-circuit current density(Jsc) of 22.77 mA cm^-2,and a fill factor(FF) of 72.38%. Additionally, due to the suitable band alignment of the TiO2/SnO2 ETL in the device, a high Vocof 1.18 V is achieved. It has been proven that the TiO2/SnO2 bilayer is a promising alternative ETL for high efficiency PSCs.

Synergistic high efficiency and low energy loss of all-small-molecule organic solar cells based on benzotriazole-basedπ-bridge unit

Reducing energy loss(V_(loss))is one of the most crucial challenges in organic photovoltaic cells.The V_(loss),determined by the differences between the optical band gap(E_(g))of the active layer material and the open-circuit voltage(V_(oc))of the device,is generally alleviated by lowering the energy difference between the lowest unoccupied molecular orbital(LUMO)and highest occupied molecular orbital(HOMO)level of the donor(D)and acceptor(A).In this work,we synthesized two A-π-D-π-A-type small-molecule donors(SMDs)SM-benzotriazole(BTz)-1 and SM-BTz-2 by introducing a BTzπ-bridge unit and terminal regulation.The BTzπ-bridge unit significantly lowers the HOMO energy level of SMDs,resulting in high V_(oc)and high mobility,achieving a balance of low energy loss(<0.5 eV)and high efficiency.Ultimately,the organic solar cells based on SM-BTz-2 as the donor and Y6 as the acceptor obtain a high V_(oc)of 0.91 V,J_(sc) of 22.8 mA cm^(−2),fill factor of 68%,and power conversion efficiency(PCE)of 14.12%,which is one of the highest efficiencies based on the SMDs with triazoleπ-bridges to date.What’s more,the BTzπ-bridge unit is a potential unit that can improve mobility and reduce energy loss.

Anionic surfactant anchoring enables 23.4%efficient and stable perovskite solar cells

Nonradiative recombination losses at defects in metal halide perovskite films are responsible for hindering the improvement of the photovoltaic performance and stability of perovskite solar cells(PSCs).Here,we report a feasible multifunctional additive strategy that uses cesium stearate to passivate defects in perovskite films and simultaneously enhances the tolerance to light and moisture stress.Nonradiative recombination losses are effectively suppressed in target films that exhibit improved crystallinity,low trap-state density,and enhanced carrier separation and transportation.The present strategy hence boosts the power conversion efficiency of the pi-n structured PSC to 23.41%.Our device also shows good stability in ambient air without encapsulation,maintaining 91.6%of the initial efficiency after 720 h.

Efficient solar fuel production with a high-pressure CO_(2)-captured liquid feed

We demonstrated an efficient solar photovoltaic-powered electrochemical CO_(2) reduction device with a high-pressure CO_(2)-captured liquid feed.In an“air-to-barrel”picture,this device holds promise to avoid both high-temperature gaseous CO_(2) regeneration and high energy-cost gas product separation steps,while these steps are necessary for devices with a gaseous CO_(2) feed.To date,solar fuel production with a CO_(2)-saturated liquid feed suffers from high over-potential to suppress the hydrogen evolution reaction and consequently,low solar-to-chemical(STC)energy conversion efficiency.Here,we presented a distinct high-pressure operando strategy,i.e.,we took extra advantage of the high pressure in catalyst synthesis besides in the period of the CO_(2) reduction reaction(CO_(2)RR).The power of this strategy was demonstrated by a proof-of-concept device in which a representative copper catalyst was first synthesized in operando in a high-pressure(50 bar)CO_(2)-saturated KHCO3 solution,and then this high-pressure CO_(2)-captured liquid was converted to solar fuel using the operando synthesized Cu catalyst.This Cu catalyst achieved 95%CO_(2)RR selectivity at the recorded low potential of−0.3 V vs.RHE enabled by the combination of operando facet engineering and oxide derivation.Furthermore,this device achieved a record-high STC efficiency of 21.6%under outdoor illumination,superior to other CO_(2)-saturated liquid-fed devices,and compared favorably to gaseous CO_(2)-fed devices.