Stability of mixed-halide wide bandgap perovskite solar cells: Strategies and progress

Benefiting from the superior optoelectronic properties and low-cost manufacturing techniques,mixedhalide wide bandgap(WBG)perovskite solar cells(PSCs)are currently considered as ideal top cells for fabricating multi-junction or tandem solar cells,which are designed to beyond the Shockley-Queisser(S-Q)limit of single-junction solar cells.However,the poor long-term operational stability of WBG PSCs limits their further employment and hinders the marketization of multi-junction or tandem solar cells.In this review,recent progresses on improving environmental stability of mixed-halide WBG PSCs through different strategies,including compositional engineering,additive engineering,interface engineering,and other strategies,are summarized.Then,the outlook and potential direction are discussed and explored to promote the further development of WBG PSCs and their applications in multijunction or tandem solar cells.

Thermoluminescence Response and Its Deconvolution on Crystalline Higher Order Mixtures of Alkali Halides Exposed to Gamma-Rays for Dosimetric Use

Alkali halides crystals have been the subject of intense research. High order crystalline one phase mixtures （high order： more that binary） studied by TL （thermoluminiscence technique） proved having persistent peaks along the time after the radiation to which they are exposed. In general in alkali halide crystals the traps associated with highest recorded temperature peaks in the TL due to radiation damage have greater permanence in time too. These features are useful for dosimetric applications. In this work, temperature thermoluminescence glow peaks of ternary and quaternary mixed alkali halide crystals have been studied. The study has been focused on their high temperature glow peaks after being subjected to thermal treatments at 373, 573, and 673 K. The glow peaks of high temperature were isolated and studied 24 h and 48 h after irradiation. The parameters of the recombination processes associated to these peaks were obtained using a glow peak shape method. Orders of kinetics were higher than 1.0 and the activation energy greater than 1.2 eV. The results suggest that such materials have a high potential as dosimeter and energy storage materials.

Growth of KCl_1–xBr_xMixed Crystals with Different Composition Percent and Study of KBr Concentration Effect on Optical Characteristics of Mixed Crystals

In the present research, mixed crystals KCl1–xBrx (x = 0.1, 0.3, 0.5, 0.7 & 0.9) were grown by Czochralski method. Then some analysis such as chemical etching, XRD, and absorbing spectrum were established on the irradiated crystals by γ-ray. The results of this research show that configuration of defects in mixed crystals in contrast with pure crystals is different. Somehow that type and percentage of cumulative composition cause to changing in lattice parameter and lattice defect density in alkali halide crystals and finally change optical properties of crystal.

Optical absorption of Tl^+ ions in KBr_(1-x)I_x:TlI mixed crystals

Optical absorption spectra of the mixed crystals of KBr1-xIx:Tl+ crystals studied at room temperature are reported.The absorption spectra indicated the appearance of additional bands on the low energy side of the Characteristic A,B and C absorption bands of KBr:Tl+ single crystals with increasing iodine composition.Comparing with earlier reports,the additional bands were attributed to the complex Tl+centers in the mixed configuration surrounded by Br-and I-ions as nearest neighbors.The absorption spectra of gamma irradiated mixed crystals showed F band,which shifts towards low energy side with the composition of iodine ions in the mixed crystals.

Lattice reconstruction for mixed-halide blue perovskite light-emitting diodes with high brightness,outstanding color stability and low efficiency roll-off

We report a simple,effective,and universal lattice reconstruction approach to improve the quality of perovskite films by using nonpolar solvents with high Gutmann donor numbers(DNs).We find that high-DN nonpolar solvents,for instance,ethyl acetate,can interact with perovskite precursors.Such a solvent can make the perovskite lattice more ordered and“harder”and promote the formation of heterostructures with low-dimensional perovskite impurities and residual solvent molecules.As a result,the latticereconstructed perovskite films exhibit reduced defect densities and suppressed ion migration.The resultant mixed-halide blue perovskite light-emitting diodes(PeLEDs)show greatly enhanced tolerance to high driving current densities and voltages,demonstrating high brightness,outstanding color stability and low efficiency roll-off.Our work provides a deep understanding of the interactions between nonpolar solvents and perovskites and offers useful guidelines for further development of high-power PeLEDs.

Role of chloride on the instability of blue emitting mixed‑halide perovskites

Although perovskite light-emitting diodes(PeLEDs)have seen unprecedented development in device efciency over the past decade,they sufer signifcantly from poor operational stability.This is especially true for blue PeLEDs,whose operational lifetime remains orders of magnitude behind their green and red counterparts.Here,we systematically investigate this efciency-stability discrepancy in a series of green-to blue-emitting PeLEDs based on mixed Br/Cl-perovskites.We fnd that chloride incorporation,while having only a limited impact on efciency,detrimentally afects device stability even in small amounts.Device lifetime drops exponentially with increasing Cl-content,accompanied by an increased rate of change in electrical properties during operation.We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice due to an increased chemically and structurally disordered landscape with reduced migration barriers.Our results indicate that the stability enhancement for PeLEDs might require diferent strategies from those used for improving efciency.

有机硅聚合物负载硫、膦混合双齿钯配合物的合成与催化性能

通过聚 4 硫杂 6 二苯膦己基硅氧烷配体和氯化钯于 60℃在丙酮中反应 72h ,合成了二氧化硅固载的聚 4 硫杂 6 二苯膦己基硅氧烷钯配合物 ,并用元素分析、X射线光电子能谱 (XPS)对其结构进行了表征。研究结果表明 ,催化量的标题钯配合物对芳基卤化物的Heck羰基化反应在常压下都有较高反应活性 ,而且芳基碘化物的反应活性明显高于相应的芳基溴化物。该负载型钯催化剂可回收再用多次 。

水溶液中碱金属卤化物-非电解质的焓对作用系数

根据实验结果获得了 2 98 15K碱金属氯化物 乙醇在水中的焓对作用系数 ,并引述了部分文献值 ,对它们进行了分析和讨论 .将基团加和性的概念应用于NaCl,NaI 非电解质的相互作用 ,得到官能团相互作用参数hNi.

碱土金属复卤化物的能隙计算及化学键离子性的修正

从Ｌｏｒｅｎｔｓ固态电子理论出发，导出一能隙的近似计算公式，表明固体的电子态和晶体结构决定了固体的能隙。对碱土金属复卤化物的能隙进行了计算，结果合理。同时考虑电负性差和原子间距，对传统化学键离子性进行了修正。计算结果和理论分析都表明，修正后的离子性能更合理地表征化合物的化学键性质。

MnF_2—BaCl_2玻璃新型红外光纤材料损耗潜力的评估

以MnF_2-BaCl_2玻璃为例,首次估计了混合卤化物玻璃的最低损耗。先对玻璃的Rayleigh散射因子进行理论估算,然后采用实验外推的方法测量了玻璃的多声子吸收参数,最后得到(MnF_2)_(60)(BaCl_2)_40玻璃的最低损耗约0.0011dB/km(λ_(min)=3.8μm)。从低损耗角度证明了MnF_2—BaCl_2玻璃是一类很有应用前景的红外光纤材料。

混合金属卤化物中的电荷转移

采用双带Ｐｅｉｅｒｌｓ＿Ｈｕｂｂａｒｄ模型研究混合金属卤化物ＰｔＸｘＸ′１－ｘ，发现电荷会穿过界面在两单体内自发转移，从而导致极化子的生产．随着电子－电子（ｅ－ｅ）相互作用强度的增加。

Pb7F(12)Br2：一个具有较高激光损伤阈值的潜在中红外非线性光学晶体材料

对一个含Pb的混合卤化物Pb_7F_(12)Br_2进行了合成及单晶结构与性能测试,并首次对它的各种与非线性光学材料相关的主要性能进行了研究。发现该化合物的光学带隙宽达4.32 e V,粉末激光损伤阈值为25 MW·cm-2,远高于同等测试条件下商品化红外非线性光学晶体材料AgGaS_2的粉末激光损伤阈值(<5.2 MW·cm-2),它的粉末倍频效应为KDP(KH2PO4)的1.5倍并能够实现相位匹配,粉末透光范围宽为0.3~14μm,热分解温度超过650℃,展示了较好的综合性能。

混合卤化物钙钛矿中的光致相分离效应

卤化物钙钛矿材料由于具有良好的光电特性和低廉的制造成本引起了人们的普遍关注。卤化物钙钛矿太阳能电池被认为有望成为下一代主流的光伏技术,其最高光电转化效率在短短的数年间提升至25.2%。特别地,混合卤化物钙钛矿的带隙能够通过改变卤素比例进行调整,因此其是制备串联太阳能电池顶部吸收层和发光二极管活性层的理想材料。然而,混合卤化物钙钛矿在光照下呈现出可逆的卤素分离现象。这种不稳定效应显著影响材料的光物理特性,严重限制了混合卤化物钙钛矿的应用。因此,近五年来学者们对其进行了大量的研究,旨在揭示光致卤素分离的基本机制,以及从化学计量和制备工艺等方面多角度探讨抑制这种不稳定效应的方法。目前,通过光谱表征与物相分析等技术,研究者们逐渐认识到混合卤化物钙钛矿中的光致相分离效应是一种内在的不稳定性,并受到热力学和动力学的共同影响。研究表明,选择合适的组分以及调控光照、温度等条件可以减轻卤素分离的程度;此外,钝化表面缺陷或控制结晶度也能够在一定程度上提高薄膜的光稳定性。然而,人们对光致相分离效应的认识仍不全面,提高混合卤化物钙钛矿光稳定性的策略也没有得到充分的研究。本文以当前典型的混合卤化物钙钛矿材料MAPb(I 1-x Br x)3为主要研究对象,回顾并分析目前对光致相分离效应的相关实验认识,结合理论分析对其发生机理进行分类阐述,最后对抑制光致相分离效应的研究进展进行了总结,以期为开发出具有光稳定性的混合卤化物钙钛矿材料提供参考。

NaF-NaCl熔融系统的分子动力学模拟

用分子动力学模拟方法,分别采用带电刚性球势、Fumi＿Tosi势和改进的Fumi＿Tosi势研究了熔融NaF＿NaCl系统的混合效应。模拟结果表明:采用带电刚性球势、Fumi＿Tosi势得到的混杂焓只在富Cl-端与实验值定性一致,而改进的Fumi＿Tosi势的混杂焓在两端都与实验值定性一致,即在NaF一端为弱吸热,而在NaCl一端为弱放热。分析表明:前者低估了极化对混杂焓的贡献。

采用硫氰酸铵添加剂的高效天蓝色钙钛矿发光二极管

金属卤化物钙钛矿发光器件具有可溶液加工、高发光效率和良好色纯度等诸多优良特性,受到了广泛的关注,但蓝色钙钛矿发光器件发光效率和光谱稳定性等方面的问题限制了钙钛矿材料在照明和显示领域的进一步发展.本工作研究硫氰酸铵添加剂对准二维混合卤化物钙钛矿薄膜形貌、结晶度、光物理和电致发光特性的影响.结果表明硫氰酸铵能有效钝化准二维混合卤化物钙钛矿薄膜的缺陷,提高结晶度,调节相分布,从而改善其电荷传输特性和发光效率.硫氰酸铵浓度为20%的准二维钙钛矿发光二极管的发光峰值波长位于486 nm处,器件的最大外量子效率为5.83%,最大亮度为1258 cd/m^(2),分别比未添加硫氰酸铵的器件提升了6.7倍和3.6倍,同时器件发光光谱稳定性和驱动稳定性也得到了明显的提升.本研究为提高蓝色准二维混合卤化物钙钛矿发光二极管的特性提供了一种简单有效的方法.

全无机混合卤化物钙钛矿量子点CsPbBrxI3-x相分离研究

混合卤化物钙钛矿量子点CsPbBr x I 3-x的带隙高度可调,是光伏和光电领域有广泛用途的纳米材料.在激光连续照射下发生的相分离会降低光电器件的效率,严重影响混合卤化物钙钛矿纳米晶在器件中的应用.本文制备了CsPbBr 1.5 I 1.5和CsPbBrI 2钙钛矿量子点薄膜,对激光激发下的相分离行为与卤化物组成比例、光照时间、激光功率和旋涂浓度的关系进行了研究.研究发现:在不同光照时间、激光功率和旋涂浓度条件下,CsPbBr 1.5 I 1.5量子点薄膜都产生了光谱蓝移的相分离,随后在黑暗下放置一段时间后再次进行测量,发现这种相分离是可逆的;而制备的CsPbBrI 2量子点薄膜在不同功率、光照时间、旋涂浓度下都很稳定,没有发生相分离,光谱只有略微蓝移.

基于长链胺及聚合物的高效蓝色发光器件

为了促进钙钛矿发光器件在显示和照明方面的应用,钙钛矿蓝光器件的研究受到广泛关注.在混卤素钙钛矿发光层MAPbBr_(2)Cl中引入长链丁基胺阳离子和聚合物添加剂聚环氧乙烷,通过减小晶粒尺寸,钝化缺陷,较好地抑制了离子迁移与非辐射复合.采用这种方法制备了发光最大波长位于484 nm、最大亮度为2876 cd/m^(2)和最高电流效率为3.7 Cd/A的天蓝色钙钛矿发光器件,较发光层为MAPbBr_(2)Cl器件的效率提高了近15倍.

基于大晶粒MA0.7FA0.3PbI3的薄膜光探测器

为了研究大晶粒高质量钙钛矿薄膜对光探测器的影响,制备了晶粒尺寸超过2μm的MA0.7FA0.3PbI3薄膜,并基于该薄膜制备了光电导型的光探测器(MCP-PD)。基于该薄膜的光探测器在532 nm和3 V偏置电压下获得了高响应度(0.905 A/W)和探测度(3.18×1012 Jones)。在相似性能条件下,基于大晶粒尺寸薄膜制备的MCP-PD还表现出较快的响应速度。实验结果表明,大晶粒尺寸的薄膜降低了晶界对载流子传输的阻碍,提升了光探测器的响应度、探测度及响应速度。

稳定高效混合卤素钙钛矿基发光二极管的制备

可以通过调节卤化物的化学计量比来调节带隙是有机-无机杂化钙钛矿的一个显著优点,这在串联太阳能电池、发射波长可调的发光二极管(LED)及激光等方面起着至关重要的作用。但是,光照或施加偏压会引起混合卤素钙钛矿相分离,导致富碘区域的形成、光伏器件开路电压降低和发光LED的发射波长被钉扎在红外区域。通过将一种具有自组装作用的有机胺长链覆盖在混合卤化物钙钛矿纳米晶的表面,抑制相分离,得到了稳定发射波长LED,并且其外部量子效率提高至2%。

通过后处理诱导的相调控增强铯铜卤化物纳米晶发光二极管性能

铯铜卤化物由于其高光致发光量子效率(PLQE)和无毒性而引起了越来越多的关注,适用于发光二极管(LED)应用。然而,目前的铜卤化物薄膜制备方法无法同时满足高性能、环保和良好环境适应性的要求。在这里,我们展示了一种简便的方法,其结合了传统的纳米晶方法和前驱体溶液方法的优点。通过使用适当的醇处理Cs_(3)Cu_(2)I_(5)纳米晶薄膜,形成了具有增强的PLQE和改善的能级匹配性的Cs_(3)Cu_(2)I_(5)/CsCu_(2)I_(3)混合维度铜卤化物,将铜卤化物LED的EQE提高到0.8%,处于无铅金属卤化物纳米晶LED的最高效率之一。这项工作为以环境友好方式制备高性能无铅LED提供了新的策略。