白炽灯电光转化率的测定及其实验条件的研究

1 问题的提出 新的物理课程标准指出,在教学中不仅要重视知识的传授,而且要重视对学生进行物理方法、探究能力的培养.在此,本文以白炽灯泡的电光转化率为切入点,利用了模型法、控制变量法、曲线改直等多种方法测定了白炽灯的电光转化率并对实验条件进行了初步的研究,以此抛砖引玉,供大家参考.

一个研究性课题的设计——白炽灯泡电光转化率的测定

1 问题的提出 中学物理教学中,在讲到能的转化和守恒定律时,几乎所有教师都会给学生举出的一个例子是:白炽灯泡发光时,消耗一定的电能,一部分转化为有用的光能,另一部分则转化为无用的热能白白散失掉了;还会让学生回忆用手触摸发光灯泡时所感受到烫手感觉。但是,这时总会有学生反问教师:到底有多少电能转化为光能,有多少损失掉了呢?教师往往被问得措手不及,情急中用诸如“这个问题不重要。

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.

Enhanced photoelectric conversion efficiency of dye-sensitized solar cells by the synergetic effect of NaYF_4:Er^(3+)/Yb^(3+) and g-C_3N_4

TiO2-NaYF4：Er^3＋/Yb^3＋-C3N4 composite photoanodes were successfully designed for the first time. The photoelectric conversion efficiency of TiO2-NaYF4：Er^3＋/Yb^3＋ C3N4 composite cell can result an efficiency of 7.37%, which is higher than those of pure TiO2 cell and TiO2-C3N4 composite cell. The enhancement of the efficiency can be attributed to the synergetic effect of NaYF4：Er^3＋/Yb^3＋ and C3N4. Elec- trochemical impedance spectroscopy analysis revealed that the interfacial resistance of the TiO2-dyelI3^-/I^- electrolyte interface of TiO2-NaYF4：Er^3＋/Yb^3＋-C3N4 composites cell was much smaller than that of pure TiO2 cell. In addition, the TiO2-NaYF4：Er^3＋/Yb^3＋-C3N4 composite cell had longer electron recombination time and shorter electron transport time than that of pure TiO2 cell.

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%.

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.

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.

An integrated thermoelectric-assisted photoelectrochemical system to boost water splitting

Common solar-driven photoelectrochemical(PEC) cells for water splitting were designed by using semiconducting photoactive materials as working photoelectrodes to capture sunlight. Due to the thermodynamic requirement of 1.23 eV and kinetic energy loss of about 0.6 eV, a photo-voltage of 1.8 V produced by PEC cells is generally required for spontaneous water splitting. Therefore, the minimum bandgap of1.8 eV is demanded for photoactive materials in single-photoelectrode PEC cells, and the bandgap of about 1 eV for back photoactive materials is appropriate in tandem PEC cells. All these PEC cells cannot effectively utilize the infrared light from 1250 to 2500 nm. In order to realize the full spectrum utilization of solar light, here, we develop a solar-driven PEC water splitting system integrated with a thermoelectric device. The key feature of this system is that the thermoelectric device produces a voltage as an additional bias for the PEC system by using the temperature difference between the incident infrared-light heated aqueous electrolyte in the PEC cell as the hot source and unirradiated external water as the cold source. Compared to a reference PEC system without the thermoelectric device, this system has a significantly improved overall water splitting activity of 1.6 times and may provide a strategy for accelerating the application of full spectrum solar light-driven PEC cells for hydrogen production.

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.

Boosting optoelectronic performance of MAPbI3 perovskite solar cells via ethylammonium chloride additive engineering

The quality of the perovskite light absorption layer plays a dynamic role in the photovoltaic properties of solar cells.The existing methods to prepare methylammonium lead iodide(MAPbI3)films render substantial structural defect density,particularly at the grain boundaries and film surface,constituting a challenge that hinders the further optoelectronic enhancement of perovskite solar cells.Herein,a unique approach was introduced:using a simple ethylammonium chloride(EACl)additive in perovskite precursor mixture to produce high-quality MAPbI3 thin films.The results indicated that EACl could encourage perovskite crystal growth without experiencing the intermediate phase formation and would evaporate from the perovskite after annealing.Additionally,a gradient perovskite structure was achieved using this technique,which impressively enhanced the performance of the perovskite films.A high power conversion efficiency(PCE)of 20.03%was achieved under the optimal amount of EACl,and the resultant efficient device could retain over 89%of the original PCE after aging for 1000 h at room temperature.This novel technique leads to a facile fabrication of highquality and less-defect perovskite thin films for competent and stable devices.

Van der Waals epitaxial growth of two-dimensional PbSe and its high-performance heterostructure devices

Inspired by the great success of ultrathin two-dimensional(2D)layered crystals,more and more attention is being paid to preparing 2D nanostructures from non-layered materials.They can significantly enrich the 2D materials and 2D heterostructures family,extend their application prospects,and bring us distinct properties from their bulk counterparts due to the strong 2D confinement effect.However,the realization of 2D non-layered semiconductors with strong light-harvesting capability and the ability to construct high-performance 2D heterostructures is still a critical challenge.Herein,we successfully synthesized 2D PbSe semiconductors with a large lateral dimension and ultrathin thickness via van der Waals epitaxy.The fabricated 2D PbSe device exhibits good electrical conductivity and superior multi-wavelength photoresponse performance with high responsivity(∼10^(3) A/W)and impressive detectivity(∼2×10^(11) Jones).Furthermore,we demonstrate that 2D PbSe nanosheets can serve as component units for constructing high-performance heterostructure devices.With our strategy,ultrahigh current on/off ratio(∼10^(8))and rectification ratio(∼10^()6),as well as high responsivity(∼3×10^(3) A/W)and detectivity(∼7×10^(12) Jones),can be achieved in PbSe/MoS_(2) back-gated transistors.These results indicate that 2D PbSe nanosheets and their heterostructures have tremendous applications potential in electrical and optoelectronic devices.