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金属卤化物钙钛矿材料作为一种新型发光材料, 具有半峰宽窄(FWHM = 20 nm)、带隙可调(380—1000 nm)、色纯度高、光致发光量子产率高(photoluminescence quantum yield, PLQY)、电荷传输性能优良、材料成本低等优点, 在各种光电子领域具有广泛应用前景[1-5], 例如钙钛矿激光器(perovskite lasers)[6,7]、钙钛矿发光二极管(perovskite light emitting diodes, PeLEDs)[8-10]、钙钛矿太阳能电池(perovskite solar cells, PSCs)[11,12]等. 2014年, Tan等[13]通过调控钙钛矿前驱体溶液中的卤化物组分, 成功制备出在室温条件下工作的近红外器件与绿光器件, 外量子效率(external quantum efficiency, EQE)分别达到了0.76%与0.1%. PeLEDs的首次出现引发了科研人员对钙钛矿发光器件的研究热潮, 研究人员通过调控钙钛矿前驱体溶液的化学计量数[14,15]、钝化薄膜表面缺陷[16,17]和尺寸工程[18,19]等多种策略, 大幅提高了PeLEDs的光电性能, 绿光、红光、近红外PeLEDs的EQE均已超过20%[10,20,21], 接近有机发光二极管 (organic light emitting diodes, OLEDs)的水平. 蓝光PeLEDs的EQE也达到了10%左右[22,23], 与其他颜色相比, 效率仍然较低, 阻碍了钙钛矿在全彩显示和固态照明的实际应用.
蓝光PeLEDs性能不佳可归因于较差的薄膜表面覆盖率、晶界自身的缺陷引起的漏电流较大、非辐射复合较强等. 早在2015年, Kumawat等[24]通过调节溴/氯元素比例, 首次制备出基于MAPbBr1.08Cl1.92的三维蓝光PeLEDs, 器件亮度及EQE分别为1.7 cd·m–2, 0.0003%, 对器件性能影响最大的因素是较差的薄膜质量. 在此基础上, Kim等[25]通过混合A位离子(Cs+, MA+, FA+)进一步提高器件的电学性能, 电致发光(electroluminescence, EL)峰位于475 nm, 对应的亮度和EQE分别达到3567 cd·m–2, 1.7%. 由于三维钙钛矿薄膜质量差, 研究人员在蓝光钙钛矿前驱体中引入长链有机胺阳离子形成准二维结构(quasi-two-dimensional, Quasi-2D), 如乙基胺盐(EA+)、丁基胺盐(BA+)、苯乙基胺盐(PEA+)、苯乙基胺盐(PBA+)、2-苯氧基乙胺(POEA)[18,19,26-28]. 钙钛矿材料由块状结构转变为层状结构, 成膜质量明显提高, 薄膜粗糙度大幅降低. 由于激子结合能的增大和载流子的集中, 更高的光致发光量子产率得以实现. 但由于器件内部能量传递效率低, 器件可能会出现多个EL发光峰, 且在三维钙钛矿转变为准二维钙钛矿的过程中, 由于晶粒尺寸的减小可能会在表面或晶界处引入更多缺陷. 此外, 基于CsPbBr3–yCly的准二维钙钛矿材料中混合卤化物钙钛矿固有的相位不稳定性, 工作时发光光谱会随电压的增加而红移, 阻碍了蓝光PeLEDs的实际应用[18,27-29]. 已有文献报道, 引入碱金属离子(如Rb+)或稀有金属离子(如Y3+)可以抑制卤素迁移, 器件运行过程中展现了较好的光谱稳定性[23,30]. 在钙钛矿前驱体溶液中加入合适的添加剂, 可以改善薄膜的均匀性及晶粒的覆盖范围, 这些小晶粒能够在空间上产生激子扩散或降低晶界处的缺陷密度, 从而抑制光致发光猝灭, 避免了界面和钙钛矿薄膜中因离子缺陷(如卤化物空位)增加的非辐射复合损失, 器件的光电性能得到提高.
本文以准二维钙钛矿PEAxCsPbBr3–yCly为基准溶液, 加入添加剂聚乙二醇(PEG)和溴化钾(KBr). 路易斯碱PEG可以补偿部分电荷, 钝化钙钛矿薄膜中的缺陷[16]. 无机金属溴化物KBr可调控钙钛矿晶粒的生长过程, K+对钙钛矿的生长有促进作用, 有助于形成光滑致密且尺寸更小的钙钛矿薄膜, 消除界面缺陷, 抑制离子迁移, 从而使器件工作时光谱稳定性得到提高[31,32]. 在PEG-KBr的协同作用下, 蓝光PeLEDs表现出优异的光电性能, 半峰宽窄(FWHM = 20 nm), 色纯度高(色坐标为(0.0747, 0.2570)), 在波长488 nm处最大亮度为1049 cd·m–2, 最大电流效率为5.68 cd·A–1, 峰值EQE达到4.6%, 且外加电压下光谱稳定性良好.
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将摩尔比为2.6∶1∶1的溴化铯(CsBr为0.2 mmol·mL–1, TCI公司, 纯度99.0%)、溴化铅(PbBr2, TCI公司, 纯度99.0%)、氯化铅(PbCl2, 西安宝莱特光电科技有限公司, 纯度99.99%)与质量分数为10 wt%的苯乙基溴化铵(PEABr, 博润新材料公司, 纯度99.5%)溶于二甲基亚砜(DMSO, Alfa Aesar公司, 纯度99.9%)中, 制备成蓝光钙钛矿前驱体溶液.
为了优化钙钛矿成膜质量, 质量分数为3.3 wt%的聚乙二醇(PEG, MACKLIN公司, 平均Mv为600000)加入至钙钛矿前驱体溶液中.
为了改善发光光谱在外加电压下的红移现象, 在溶液中加入浓度为2 mg·ml–1的溴化钾(KBr, Aladdin公司, 纯度99.5%). 所有制备的前驱体溶液在40 ℃下搅拌数小时, 静置备用. 以上实验材料均直接购买使用, 没有进一步处理及提纯. 制备流程如图1所示.
图 1 基于PEAxCsPbBr3–yCly + PEG + KBr钙钛矿前驱体溶液的合成路线
Figure 1. Synthesis of PEAxCsPbBr3–yCly + PEG + KBr based perovskite precursor solution
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将氧化铟锡(indium tin oxide, ITO)玻璃基片用丙酮、乙醇、异丙醇溶剂分别超声清洗15 min, 放入110 ℃烘箱中烘干残留溶剂, 30 min后取出备用. 在薄膜沉积之前, 干燥的ITO玻璃基板用紫外线臭氧处理20 min, 以增强表面亲水性. 过滤后的聚(3, 4-乙基二氧噻吩): 聚(苯乙烯磺酸盐) (PEDOT:PSS, Clevios Al 4083)旋涂在ITO玻璃基板上, 转速为4000 rpm, 旋涂好后的基片在150 ℃的加热台处退火15 min, 以除去残留的水分. 退火后, 样品转移至充满氮气的手套箱中, 三种钙钛矿前驱体溶液过滤后, 旋涂在PEDOT:PSS基底上, 转速设定为3000 rpm, 时间为60 s, 随即放至70 ℃的加热台处退火8 min. 将样品转移至有机热蒸发仪中(Trovato, 基准压力 <3× 10–7 Torr (1 Torr ≈ 133.322 Pa), 依次蒸镀电子传输层2, 2′, 2″-(1, 3, 5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi, Nichem公司, 纯度99.0%)、电子注入层氟化锂(LiF, MACKLIN公司, 纯度99.99%)和Al电极, 厚度分别为50, 1和100 nm. 蒸镀后对PeLEDs器件进行简易封装并测试其电学性能, 测定PeLEDs的有效面积为10 mm2.
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钙钛矿薄膜的表面微观形貌利用扫描电子显微镜(SEM, Zeiss Supra 55)进行表征. 薄膜物质的晶体结构使用X 射线衍射分析仪(XRD, PANalytical X’Pert Pro)进行分析, 以 Cu Kα作为射线源 (λ = 0.154 nm). 用荧光光谱仪(PL, Horiba Jobin Yvon)测定了稳态光致发光光谱, 瞬态光致发光光谱使用Quantaurus-Tau荧光寿命光谱仪(C11367-32, Hamamatsu Photonics)测量, 激发波长均为373 nm.
钙钛矿发光器件的电流密度-电压-亮度(J-V-L)特性曲线和电致发光(EL)光谱均由程控电源(Keithley model 2400)与光谱光度计(PhotoResearch PR670)测定. EQE值是通过积分球(Hamamatsu Photonics K.K. C9920-12)测量光通量得到的. 采用64通道ZJLS-4型老化测试系统, 在恒流模式下测试器件寿命. 以上测试与表征均在空气环境中完成.
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图2为PEAxCsPbBr3-yCly钙钛矿溶液中加入不同添加剂的表面微观形貌图, 图3为含有不同添加剂的钙钛矿晶粒尺寸分布柱状图. 不添加任何添加剂的PEAxCsPbBr3-yCly钙钛矿薄膜表面覆盖不完整, 颗粒尺寸较大(平均晶粒尺寸为38.47 nm), 低的薄膜覆盖率将会导致器件漏电流较大, 限制了器件性能(图2(a)和图3(a)). 作为对比, 纯PEG的加入可以抑制快速生长的钙钛矿晶粒, 降低晶粒尺寸(平均晶粒尺寸减小至24.09 nm), 同时由于聚合物添加剂自身较好的溶液可加工性, 薄膜表面粗糙度显著降低, 覆盖率大幅度提高, 提高薄膜的覆盖度与均匀性可有效减少非辐射复合造成的电流损失(图2(b)和图3(b))[33]. 纯KBr的加入可以使晶粒尺寸变得更小(平均晶粒尺寸为20.50 nm), 研究表明小晶粒可以在空间上限制激子扩散长度, 增大激子辐射复合的可能性[34]. 同时KBr可以减缓结晶过程, 使钙钛矿结晶更加完美[31](图2(c)和图3(c)). PEAxCsPbBr3–yCly + PEG + KBr钙钛矿薄膜表面均一平整, 覆盖度最高, 晶粒尺寸最均匀, 平均粒径仅为17.53 nm(图2(d)和图3(d)).
图 2 含有不同添加剂的PEAxCsPbBr3-yCly钙钛矿薄膜SEM图像, 标尺为200 nm
Figure 2. SEM images of PEAxCsPbBr3-yCly perovskite films with different additives, the scale bar is 200 nm
图 3 含有不同添加剂的PEAxCsPbBr3-yCly钙钛矿晶粒尺寸分布柱状图
Figure 3. Histograms of grain size distributions of PEAxCsPbBr3-yCly perovskite films with different additives.
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图4为三个样品ITO/PEDOT:PSS/PEAxCsPb
Br3–yCly, ITO/PEDOT:PSS/PEAxCsPbBr3–yCly + PEG, ITO/PEDOT:PSS/PEAxCsPbBr3–yCly + PEG+KBr的X射线衍射图谱(XRD). 在15.1°, 21.5°, 30.3°, 35.3°处的特征峰分别对应(100), (110), (200), (210)晶面, 加入不同添加剂的钙钛矿薄膜晶体结构以正交晶相(Pnma)为主, 与之前的报道一致[35]. 三种钙钛矿薄膜XRD峰位几乎相同, 说明添加少量的PEG或KBr对钙钛矿材料的晶体结构并无明显影响. 
图 4 含有不同添加剂的PEAxCsPbBr3-yCly钙钛矿薄膜在PEDOT:PSS上的XRD图谱
Figure 4. XRD patterns of various PEAxCsPbBr3-yCly perovskite films with different additives on PEDOT:PSS.
图5为上述三种薄膜在石英基底上的稳态光致发光光谱 (steady state photoluminescence spectroscopy)和时间分辨光致发光衰减曲线(time- resolved photoluminescence decay curves), 激发波长均为373 nm. 图5(a)所示, 纯PEAxCsPbBr3–yCly钙钛矿薄膜的光致发光峰为484 nm, 含有两种添加剂的钙钛矿薄膜光致发光峰与标件相比均出现微量红移, 为486 nm, PEG的存在可能在一定程度上抑制了PEABr形成准二维钙钛矿的过程. 如图5(b)所示, 在激发波长为373 nm时, 未含添加剂的薄膜PLQY为1.37%, 含有PEG的薄膜PLQY为4.71%, 含有PEG与KBr的薄膜PLQY为18.9%. 钙钛矿薄膜获得更高的光致发光量子产率, 有利于载流子的辐射复合发光. 如图5(c)所示, 标件钙钛矿薄膜PL寿命较短, 发光猝灭现象严重. PEG和KBr的共同存在可以延长PL寿命, 呈现出较长的PL衰减曲线. 密度泛函理论表明钙钛矿薄膜中存在的卤素空位会在带隙内产生缺陷, 可能成为非辐射复合中心, 不利于制备高效的钙钛矿发光器件[36]. 而在钙钛矿中引入合适的添加剂可以钝化钙钛矿薄膜处缺陷, 抑制薄膜中卤素空位的形成, 从而降低非辐射复合概率[16,17]. 关于界面缺陷钝化有待进一步深入研究, 探究其物理机理.
图 5 含有不同添加剂的PEAxCsPbBr3–yCly钙钛矿薄膜的光学性能表征 (a) PL光谱; (b) PLQY; (c)TRPL曲线
Figure 5. Optical characterization of PEAxCsPbBr3–yCly perovskite films with different additives: (a) PL spectroscopy; (b) PLQY; (b) TRPL decay curves.
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图6(a)为基于PEAxCsPbBr3-yCly钙钛矿薄膜的电致发光器件结构示意图, 器件结构为ITO/PEDOT:PSS/钙钛矿/TPBi/LiF/Al, 其中钙钛矿层分别为PEAxCsPbBr3–yCly, PEAxCsPbBr3–yCly + PEG, PEAxCsPbBr3–yCly +PEG+KBr. 图6(b)为整体器件的SEM截面图, 从下至上依次为玻璃, 阳极ITO, 空穴传输层PEDOT:PSS, 钙钛矿发光层, 电子传输层TPBi, 电子注入层LiF, 阴极Al.
图 6 (a) PeLEDs的器件结构示意图; (b) PeLEDs的截面SEM图像
Figure 6. (a) Device structure diagram of PeLEDs; (b) Cross-sectional SEM images of PeLEDs
图7为基于不同钙钛矿发光层器件的电学性能, 测量了器件亮度(luminance, L)、电流效率(current efficiency, CE)、功率效率(power efficiency, PE)、外量子效率(external quantum efficiency, EQE)、开启电压(voltage on, Von)、半峰宽(FWHM)、电致发光(EL)光谱等. 图7(a)为电流密度-电压-亮度(J-V-L)性能曲线, 图7(b)为电流效率-电流密度-外量子效率(CE-J-EQE)性能曲线. 对照器件的电流密度明显高于含有添加剂的器件, 结合钙钛矿薄膜的表面形貌, 可以发现没有添加剂钙钛矿薄膜的晶粒覆盖度差、存在较多孔洞, 会引起电流泄露, 空穴-电子对无法在发光层中进行有效辐射复合. 该器件表现的性能不佳, 最大亮度为779 cd·m–2, CE和EQE仅为1.62 cd·A–1和1.2%. 加入PEG后, 器件的电流密度显著降低, 亮度在一定程度上有所提高, 亮度、CE和EQE分别增长至1038 cd·m–2, 3.69 cd·A–1和3.0%. 器件性能的提高可归功于PEG的引入促进形成致密无孔洞的钙钛矿薄膜. 为了进一步提升钙钛矿薄膜的性能以及发光器件的效率, 在制备钙钛矿薄膜过程中引入双添加剂—PEG和KBr, 我们发现双添加剂的引入促使形成了高表面覆盖率、晶粒尺寸较小且均匀的钙钛矿薄膜, 最大程度地抑制了电流泄漏, 同时改善了发光器件的空穴电子注入平衡, 提高了辐射复合效率. 最终PeLEDs的CE和EQE分别达到了5.68 cd·A–1和4.6%, 相比对照器件提高了近3倍. 在器件的CE及EQE到达最高值后, 效率开始滚降, 随着电流密度的增加, 器件性能不断衰退, 这可能是源于俄歇复合引起的器件发光猝灭, 或是钙钛矿内部不断累积的电流热效应所引发[13,37]. 综上所述, 不同钙钛矿薄膜的PeLEDs电学性能变化与其薄膜形貌和其他光学性能变化相一致. 图7(c)为三种器件归一化后的EL光谱图, 发光峰在488 nm处, 半峰宽窄(FWHM = 20 nm), 均呈高斯分布, 没有分峰. 相对于PL, EL发光谱存在微量红移现象, 这可能是电荷载体与激子动力学的相互作用, 注入的载流子传输到能量较低的区域, 在更小的带隙间辐射复合[24]. 图7(d)为国际照明委员会(CIE)色坐标图, 基于PEAxCsPbBr3–yCly + PEG + KBr钙钛矿薄膜的PeLEDs可以在蓝色显色区域内发射出高纯度的蓝光, 色坐标为(0.0747, 0.2570). 表1总结了不同添加剂钙钛矿发光层的PeLEDs电学性能.
Devices Max.
L/cd·m–2CE/cd·A–1 EQE/% EL
peak/nmControl 779 1.62 1.2 488 PEG 1038 3.69 3.0 488 PEG+KBr 1049 5.68 4.6 488 表 1 含有不同添加剂钙钛矿发光层的蓝光PeLEDs性能
Table 1. The performance of blue PeLEDs with different additive perovskite materials.
图 7 含有不同添加剂的PeLEDs电学性能表征 (a)电流密度-电压-亮度(J-V-L); (b)电流效率-电流密度-外量子效率(CE-J-EQE); (c)归一化后的EL光谱图; (d)国际照明委员会(CIE)色坐标图
Figure 7. Electrical performance characteristics of PeLEDs with different additives: (a) Current density-voltage-luminance(J-V-L); (b) current efficiency-current density-external quantum efficiency(CE-J-EQE); (c) the normalized EL spectra; (d) the Commission Internationale de I’Eclairage (CIE) coordinates
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图8(a)为三种器件在空气环境下运行时的寿命衰减图, 测量的器件寿命是指在电压驱动下, 从初始亮度(L0)衰减至亮度一半 (L0/2) 时所需要的时间(T50)[38]. 当初始亮度为100 cd·m–2时(此时对照器件的电压为5.88 V, 电流密度6.039 mA·cm–2; 含有PEG的器件电压为5.90 V, 电流密度2.025 mA·cm–2; 含有PEG +KBr的器件电压为6.0 V, 电流密度1.707 mA·cm–2), 对照器件的半衰期为6.6 min, 含有PEG的器件半衰期提高至9.0 min, 而PEG与KBr同时存在的器件半衰期可达11.4 min, 比对照器件提高近一倍. 主要原因是空穴-电子对能够在钙钛矿层进行有效的辐射复合出光, 内部热量损耗现象得到显著改善. 通过对比3种器件在T0与T50时刻分别对应的EL光谱(图8(b)—图8(d)), 可以看出在T0时刻, 3种器件的EL光谱均为488 nm. 当亮度下降至初始亮度的一半时, 未含添加剂的器件(T50时EL光谱为494 nm)与只含PEG的器件(T50时EL光谱为492 nm)均发生不同程度的红移, 而含有双添加剂的器件EL光谱仍保持在488 nm, 证实了KBr的存在可以提高器件运行时的稳定性.
图 8 (a)含有不同添加剂的PeLEDs寿命特性图. 含有不同添加剂的PeLEDs在T0与T50时对应的EL光谱 (b)标准器件; (c)有PEG; (d)有PEG与KBr
Figure 8. (a) Operating lifetime characteristics of PeLEDs with different additives. The corresponding EL spectra of PeLEDs with different additives at T0 and T50: (b) Control; (c) with PEG; (d) with PEG+KBr
图9研究了KBr的引入对PeLEDs光谱稳定性的影响, 测量了施加不同电压情况下EL发光光谱的变化情况. 可以看出, 在不含KBr的器件中, 当驱动电压达到6.9 V时, EL光谱发生了微量红移(标准器件发光峰从488 nm红移至492 nm, 含有PEG的器件发光峰从488 nm红移至490 nm). 而在添加KBr的器件中, 随着驱动电压的增加, EL光谱并未发生显著变化. 为进一步证明含有KBr的器件具有光谱稳定性, 在恒压下(5.7 V)测试了不同工作时长的器件EL光谱图, 如图10所示, 在器件运行至3 min时, 未含KBr的器件光谱已经发生红移, 5 min时, 能明显看出EL光谱的变化, 而含有KBr的器件在5 min时仍保持良好的运行稳定性. 因此, 这种现象可以理解为在钙钛矿前驱体中引入KBr可以显著降低界面缺陷密度, 消除了钙钛矿膜中移动卤化物的离子缺陷, 同时还抑制离子迁移, 因此在工作电压下发光光谱的稳定性得到提高[32,39].
图 9 PeLEDs光谱稳定性 (a)标准器件; (b)有PEG; (c)有PEG与KBr
Figure 9. The spectral stability of PeLEDs: (a) Control; (b) with PEG; (c) with PEG + KBr.
图 10 5.7 V下, PeLEDs不同工作时长的EL光谱图 (a)标准器件; (b)有PEG; (c)有PEG与KBr
Figure 10. The EL spectra of PeLEDs with different working minutes at 5.7 V: (a) Control; (b) with PEG; (c) with PEG+KBr.
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综上, 在钙钛矿发光器件中, 通过PEG与KBr双添加剂的加入, 有效改善了PEAxCsPbBr3–yCly钙钛矿薄膜的形貌, 得到了表面均一、覆盖率高、晶粒尺寸较小且无孔洞的钙钛矿发光薄膜. 其中PEG用以补偿电荷、钝化缺陷, KBr用于减缓结晶过程、减小结晶尺寸, 使激子能够有效地在钙钛矿层辐射复合发光. 基于PEAxCsPbBr3-yCly+PEG + KBr发光层的钙钛矿发光器件漏电流现象被显著抑制, 最终获得高纯度蓝光PeLEDs, 最大亮度达到1049 cd·m–2, CE达到5.68 cd·A–1, EQE达到4.6%. 实验结果表明KBr的引入能够抑制Br/Cl迁移, 器件工作时光谱稳定性得到提高. 本文为实现高效稳定的蓝光PeLEDs提供了一个新思路.
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钙钛矿材料由于具备带隙易调、光致发光量子产率高、色纯度高、载流子迁移率高、可低温溶液加工、电荷传输性能优良等优点, 在照明显示领域大放异彩. 近年来, 通过控制化学计量比、尺寸工程和钝化缺陷等多种策略对钙钛矿微观结构进行调控, 极大地提高了钙钛矿发光二极管(perovskite light emitting diodes, PeLEDs)的性能. 目前,除蓝光外, 绿光、红光、近红外PeLEDs的外量子效率(EQE)均已超过20%. 造成蓝光器件性能停滞不前的主要原因是蓝光钙钛矿薄膜较差的覆盖率以及光谱不稳定. 为提高钙钛矿薄膜质量及器件性能, 本文在准二维钙钛矿材料PEAxCsPbBr3–yCly的基础上, 通过引入双添加剂聚乙二醇(PEG)和溴化钾(KBr), 钝化薄膜表面缺陷态, 减小晶粒尺寸, 抑制离子迁移与非辐射复合损耗, 进而提升蓝光钙钛矿器件的效率及光谱稳定性. 最终在488 nm处获得最大亮度为1049 cd·m–2, 电流效率为5.68 cd·A–1, 外量子效率为4.6%的蓝光PeLEDs. 相比于不含添加剂的器件, 效率提升了近3倍, 且具有良好的光谱稳定性和工作寿命.Solution-processable metal halide perovskites materials have many advantages, such as adjustable band gap, high photoluminescence quantum yield (PLQY), high color purity, high carrier mobility, low temperature solution process, excellent charge transport property and so on. These make them potential application in the display field. In the past few years, the device performance of perovskite light emitting devices (PeLEDs) have been greatly improved by manipulating the perovskite microstructures through various strategies, such as stoichiometry control, dimensional engineering, defect passivation and so on. At present, except for blue PeLEDs, the external quantum efficiencies (EQEs) over 20% have been achieved for green, red, and near-infrared PeLEDs. The low efficiency of blue PeLEDs is retarding their potential applications in full-color display and solid-state lighting. The main reasons in blue PeLEDs are the poor film coverage of blue perovskite materials and the spectral instability during device operation. In order to improve the quality of perovskite film and device performance, the quasi two-dimensional perovskite materials phenylethylammonium cesium lead bromide chloride (PEAxCsPbBr3–yCly) are used as the main perovskite emission material, by partially replacing Br with Cl to enlarge their bandgap to achieve the blue emission. The Lewis base polyethyleneglycol (PEG) is introduced to passivate the surface trapping defects and improve perovskite film coverage. The potassium bromide (KBr) is introduced to reduce perovskite grain size, suppress mobile ion migration and exhibit excellent spectral stability. Dual additives PEG and KBr are incorporated into the quasi-2D blue perovskite for inhibiting the nonradiative losses by passivating the traps in the perovskite films. Eventually, the PEAxCsPbBr3–yCly + PEG + KBr based blue PeLEDs with the emission peak of 488 nm are accompanied, which maximum brightness, current efficiency, and external quantum efficiency reached 1049 cd·m–2, of 5.68 cd·A–1, and of 4.6%, respectively, with high color purity (the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates is (0.0747, 0.2570)) and the narrow full width at half maximum (FWHM) of 20 nm. Compare to the devices without additives, the efficiency has increased by nearly 3 times. Furthermore, the devices also show better spectral stability and operation lifetime. This work provides an effective method of blue PeLEDs toward the practical applications.
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Keywords:
- perovskite materials /
- blue emission /
- light emitting diodes /
- defect passivation
[1] Zhang X, Liu H, Wang W, Zhang J, Xu B, Karen K L, Zheng Y, Liu S, Chen S, Wang K, Sun X W 2017 Adv. Mater. 29 1606405
Google Scholar
[2] 姚鑫, 丁艳丽, 张晓丹, 赵颖 2015 物理学报 64 038805
Google Scholar
Yao X, Ding Y L, Zhang X D, Zhao Y 2015 Acta Phys. Sin. 64 038805
Google Scholar
[3] Stranks S D, Eperon G E, Grancini G, Menelaou C, Alcocer M J, Leijtens T, Herz L M, Petrozza A, Snaith H J 2013 Science 342 341
Google Scholar
[4] Liu D, Kelly T L 2014 Nat. Photonics 8 133
Google Scholar
[5] Dong Q, Fang Y, Shao Y, Mulligan P, Qiu J, Cao L, Huang J 2015 Science 347 967
Google Scholar
[6] Brenner P, Stulz M, Kapp D, Abzieher T, Paetzold U W, Quintilla A, Howard I A, Kalt H, Lemmer U 2016 Appl. Phys. Lett. 109 141106
Google Scholar
[7] Wang Y C, Li H, Hong Y H, Hong K B, Chen F C, Hsu C H, Lee R K, Conti C, Kao T S, Lu T C 2019 ACS Nano 13 5421
Google Scholar
[8] Xiao Z G, Kerner R A, Zhao L F, Tran N L, Lee K M, Koh T W, Scholes G D, Rand B P 2017 Nat. Photonics 11 108
Google Scholar
[9] Wang N, Cheng L, Ge R, Zhang S, Miao Y, Zou W, Yi C, Sun Y, Cao Y, Yang R, Wei Y, Guo Q, Ke Y, Yu M, Jin Y, Liu Y, Ding Q, Di D, Yang L, Xing G, Tian H, Jin C, Gao F, Friend R H, Wang J, Huang W 2016 Nat. Photonics 10 699
Google Scholar
[10] Lin K, Xing J, Quan L N, de Arquer F P G, Gong X W, Lu J X, Xie L Q, Zhao W J, Zhang D, Yan C Z, Li W Q, Liu X Y, Lu Y, Kirman J, Sargent E H, Xiong Q H, Wei Z H 2018 Nature 562 245
Google Scholar
[11] Turkevych I, Kazaoui S, Belich N A, Grishko A Y, Fateev S A, Petrov A A, Urano T, Aramaki S, Kosar S, Kondo M, Goodilin E A, Graetzel M, Tarasov A B 2019 Nat. Nanotechnol. 14 57
Google Scholar
[12] Tavakoli M M, Yadav P, Prochowicz D, Sponspeller M, Osheov A, Bulovic V, Kong J 2019 Adv. Energy Mater. 9 1803587
Google Scholar
[13] Tan Z K, Moghaddam R S, Lai M L, Docampo P, Higler R, Deschler F, Price M, Sadhanala A, Pazos L M, Credgington D, Hanusch F, Bein T, Snaith H J, Friend R H 2014 Nat. Nanotechnol. 9 687
Google Scholar
[14] Cho H, Jeong S H, Park M H, Kim Y H, Wolf C, Lee C L, Heo J H, Sadhanala A, Myoung N, Yoo S, Im S H, Friend R H, Lee T W 2015 Science 350 1222
Google Scholar
[15] Yantara N, Bhaumik S, Yan F, Sabba D, Dewi H A, Mathews N, Boix P P, Demir H V, Mhaisalkar S 2015 J. Phys. Chem. Lett. 6 4360
Google Scholar
[16] Cheng L P, Huang J S, Shen Y, Li G P, Liu X K, Li W, Wang Y H, Li Y Q, Jiang Y, Gao F, Lee C S, Tang J X 2019 Adv. Opt. Mater. 7 1801534
Google Scholar
[17] Fang Z, Chen W, Shi Y, Zhao J, Chu S, Zhang J, Xiao Z 2020 Adv. Funct. Mater. 30 1909754
Google Scholar
[18] Li Z, Chen Z, Yang Y, Xue Q, Yip H L, Cao Y 2019 Nat. Commun. 10 1027
Google Scholar
[19] Wang K H, Peng Y, Ge J, Jiang S, Zhu B S, Yao J, Yin Y C, Yang J N, Zhang Q, Yao H B 2018 ACS Photonics 6 667
Google Scholar
[20] Cao Y, Wang N, Tian H, Guo J, Wei Y, Chen H, Miao Y, Zou W, Pan K, He Y, Cao H, Ke Y, Xu M, Wang Y, Yang M, Du K, Fu Z, Kong D, Dai D, Jin Y, Li G, Li H, Peng Q, Wang J, Huang W 2018 Nature 562 249
Google Scholar
[21] Xu W, Hu Q, Bai S, Bao C, Miao Y, Yuan Z, Borzda T, Barker A J, Tyukalova E, Hu Z, Kawecki M, Wang H, Yan Z, Liu X, Shi X, Uvdal K, Fahlman M, Zhang W, Duchamp M, Liu J M, Petrozza A, Wang J, Liu L M, Huang W, Gao F 2019 Nat. Photonics 13 418
Google Scholar
[22] Liu Y, Cui J, Du K, Tian H, He Z, Zhou Q, Yang Z, Deng Y, Chen D, Zuo X, Ren Y, Wang L, Zhu H, Zhao B, Di D, Wang J, Friend R H, Jin Y 2019 Nat. Photonics 13 760
Google Scholar
[23] Wang Q, Wang X, Yang Z, Zhou N, Deng Y, Zhao J, Xiao X, Rudd P, Moran A, Yan Y, Huang J 2019 Nat. Commun. 10 5633
Google Scholar
[24] Kumawat N K, Dey A, Kumar A, Gopinathan S P, Narasimhan K L, Kabra D 2015 ACS Appl. Mater. Interfaces 7 13119
Google Scholar
[25] Kim H P, Kim J, Kim B S, Kim H M, Kim J, Yusoff A R b M, Jang J, Nazeeruddin M K 2017 Adv. Opt. Mater. 5 1600920
Google Scholar
[26] Wang Q, Ren J, Peng X F, Ji X X, Yang X H 2017 ACS Appl. Mater. Interfaces 9 29901
Google Scholar
[27] Vashishtha P, Ng M, Shivarudraiah S B, Halpert J E 2018 Chem. Mater. 31 83
Google Scholar
[28] Cheng L, Cao Y, Ge R, Wei Y Q, Wang N N, Wang J P, Huang W 2017 Chin. Chem. Lett. 28 29
Google Scholar
[29] 段聪聪, 程露, 殷垚, 朱琳 2019 物理学报 68 158503
Google Scholar
Duan C C, Chen L, Yin Y, Zhu L 2019 Acta Phys. Sin. 68 158503
Google Scholar
[30] Jiang Y, Qin C, Cui M, He T, Liu K, Huang Y, Luo M, Zhang L, Xu H, Li S, Wei J, Liu Z, Wang H, Kim G H, Yuan M, Chen J 2019 Nat. Commun. 10 1868
Google Scholar
[31] Ren Z, Xiao X, Ma R, Lin H, Wang K, Sun X W, Choy W C H 2019 Adv. Funct. Mater. 29 1905339
Google Scholar
[32] Zheng F, Chen W, Bu T, Ghiggino K P, Huang F, Cheng Y, Tapping P, Kee T W, Jia B, Wen X 2019 Adv. Energy Mater. 9 1901016
Google Scholar
[33] 黎振超, 陈梓铭, 邹广锐兴, 叶轩立, 曹镛 2019 物理学报 68 158505
Google Scholar
Li Z C, Chen Z M, Zou G R X, Yip H L, Cao Y 2019 Acta Phys. Sin. 68 158505
Google Scholar
[34] Li G, Tan Z K, Di D, Lai M L, Jiang L, Lim J H W, Friend R H, Greenham N C 2015 Nano Lett. 15 2640
Google Scholar
[35] Edri E, Kirmayer S, Kulbak M, Hodes G, Cahen D 2014 J. Phys. Chem. Lett. 5 429
Google Scholar
[36] Shi H, Du M H 2014 Phys. Rev. B 90 174103
Google Scholar
[37] Zou W, Li R, Zhang S, Liu Y, Wang N, Cao Y, Miao Y, Xu M, Guo Q, Di D, Zhang L, Yi C, Gao F, Friend R H, Wang J, Huang W 2018 Nat. Commun. 9 608
Google Scholar
[38] Yang Y, Zheng Y, Cao W, Titov A, Hyvonen J, Manders J R, Xue J, Holloway P H, Qian L 2015 Nat. Photonics 9 259
Google Scholar
[39] 王继飞, 林东旭, 袁永波 2019 物理学报 68 158501
Google Scholar
Wang J F, Lin D X, Yuan Y B 2019 Acta Phys. Sin. 68 158501
Google Scholar
-
图 1 基于PEAxCsPbBr3–yCly + PEG + KBr钙钛矿前驱体溶液的合成路线
Fig. 1. Synthesis of PEAxCsPbBr3–yCly + PEG + KBr based perovskite precursor solution
图 2 含有不同添加剂的PEAxCsPbBr3-yCly钙钛矿薄膜SEM图像, 标尺为200 nm
Fig. 2. SEM images of PEAxCsPbBr3-yCly perovskite films with different additives, the scale bar is 200 nm
图 3 含有不同添加剂的PEAxCsPbBr3-yCly钙钛矿晶粒尺寸分布柱状图
Fig. 3. Histograms of grain size distributions of PEAxCsPbBr3-yCly perovskite films with different additives.
图 4 含有不同添加剂的PEAxCsPbBr3-yCly钙钛矿薄膜在PEDOT:PSS上的XRD图谱
Fig. 4. XRD patterns of various PEAxCsPbBr3-yCly perovskite films with different additives on PEDOT:PSS.
图 5 含有不同添加剂的PEAxCsPbBr3–yCly钙钛矿薄膜的光学性能表征 (a) PL光谱; (b) PLQY; (c)TRPL曲线
Fig. 5. Optical characterization of PEAxCsPbBr3–yCly perovskite films with different additives: (a) PL spectroscopy; (b) PLQY; (b) TRPL decay curves.
图 6 (a) PeLEDs的器件结构示意图; (b) PeLEDs的截面SEM图像
Fig. 6. (a) Device structure diagram of PeLEDs; (b) Cross-sectional SEM images of PeLEDs
图 7 含有不同添加剂的PeLEDs电学性能表征 (a)电流密度-电压-亮度(J-V-L); (b)电流效率-电流密度-外量子效率(CE-J-EQE); (c)归一化后的EL光谱图; (d)国际照明委员会(CIE)色坐标图
Fig. 7. Electrical performance characteristics of PeLEDs with different additives: (a) Current density-voltage-luminance(J-V-L); (b) current efficiency-current density-external quantum efficiency(CE-J-EQE); (c) the normalized EL spectra; (d) the Commission Internationale de I’Eclairage (CIE) coordinates
图 8 (a)含有不同添加剂的PeLEDs寿命特性图. 含有不同添加剂的PeLEDs在T0与T50时对应的EL光谱 (b)标准器件; (c)有PEG; (d)有PEG与KBr
Fig. 8. (a) Operating lifetime characteristics of PeLEDs with different additives. The corresponding EL spectra of PeLEDs with different additives at T0 and T50: (b) Control; (c) with PEG; (d) with PEG+KBr
图 9 PeLEDs光谱稳定性 (a)标准器件; (b)有PEG; (c)有PEG与KBr
Fig. 9. The spectral stability of PeLEDs: (a) Control; (b) with PEG; (c) with PEG + KBr.
图 10 5.7 V下, PeLEDs不同工作时长的EL光谱图 (a)标准器件; (b)有PEG; (c)有PEG与KBr
Fig. 10. The EL spectra of PeLEDs with different working minutes at 5.7 V: (a) Control; (b) with PEG; (c) with PEG+KBr.
表 1 含有不同添加剂钙钛矿发光层的蓝光PeLEDs性能
Table 1. The performance of blue PeLEDs with different additive perovskite materials.
Devices Max.
L/cd·m–2CE/cd·A–1 EQE/% EL
peak/nmControl 779 1.62 1.2 488 PEG 1038 3.69 3.0 488 PEG+KBr 1049 5.68 4.6 488 
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[1] Zhang X, Liu H, Wang W, Zhang J, Xu B, Karen K L, Zheng Y, Liu S, Chen S, Wang K, Sun X W 2017 Adv. Mater. 29 1606405
Google Scholar
[2] 姚鑫, 丁艳丽, 张晓丹, 赵颖 2015 物理学报 64 038805
Google Scholar
Yao X, Ding Y L, Zhang X D, Zhao Y 2015 Acta Phys. Sin. 64 038805
Google Scholar
[3] Stranks S D, Eperon G E, Grancini G, Menelaou C, Alcocer M J, Leijtens T, Herz L M, Petrozza A, Snaith H J 2013 Science 342 341
Google Scholar
[4] Liu D, Kelly T L 2014 Nat. Photonics 8 133
Google Scholar
[5] Dong Q, Fang Y, Shao Y, Mulligan P, Qiu J, Cao L, Huang J 2015 Science 347 967
Google Scholar
[6] Brenner P, Stulz M, Kapp D, Abzieher T, Paetzold U W, Quintilla A, Howard I A, Kalt H, Lemmer U 2016 Appl. Phys. Lett. 109 141106
Google Scholar
[7] Wang Y C, Li H, Hong Y H, Hong K B, Chen F C, Hsu C H, Lee R K, Conti C, Kao T S, Lu T C 2019 ACS Nano 13 5421
Google Scholar
[8] Xiao Z G, Kerner R A, Zhao L F, Tran N L, Lee K M, Koh T W, Scholes G D, Rand B P 2017 Nat. Photonics 11 108
Google Scholar
[9] Wang N, Cheng L, Ge R, Zhang S, Miao Y, Zou W, Yi C, Sun Y, Cao Y, Yang R, Wei Y, Guo Q, Ke Y, Yu M, Jin Y, Liu Y, Ding Q, Di D, Yang L, Xing G, Tian H, Jin C, Gao F, Friend R H, Wang J, Huang W 2016 Nat. Photonics 10 699
Google Scholar
[10] Lin K, Xing J, Quan L N, de Arquer F P G, Gong X W, Lu J X, Xie L Q, Zhao W J, Zhang D, Yan C Z, Li W Q, Liu X Y, Lu Y, Kirman J, Sargent E H, Xiong Q H, Wei Z H 2018 Nature 562 245
Google Scholar
[11] Turkevych I, Kazaoui S, Belich N A, Grishko A Y, Fateev S A, Petrov A A, Urano T, Aramaki S, Kosar S, Kondo M, Goodilin E A, Graetzel M, Tarasov A B 2019 Nat. Nanotechnol. 14 57
Google Scholar
[12] Tavakoli M M, Yadav P, Prochowicz D, Sponspeller M, Osheov A, Bulovic V, Kong J 2019 Adv. Energy Mater. 9 1803587
Google Scholar
[13] Tan Z K, Moghaddam R S, Lai M L, Docampo P, Higler R, Deschler F, Price M, Sadhanala A, Pazos L M, Credgington D, Hanusch F, Bein T, Snaith H J, Friend R H 2014 Nat. Nanotechnol. 9 687
Google Scholar
[14] Cho H, Jeong S H, Park M H, Kim Y H, Wolf C, Lee C L, Heo J H, Sadhanala A, Myoung N, Yoo S, Im S H, Friend R H, Lee T W 2015 Science 350 1222
Google Scholar
[15] Yantara N, Bhaumik S, Yan F, Sabba D, Dewi H A, Mathews N, Boix P P, Demir H V, Mhaisalkar S 2015 J. Phys. Chem. Lett. 6 4360
Google Scholar
[16] Cheng L P, Huang J S, Shen Y, Li G P, Liu X K, Li W, Wang Y H, Li Y Q, Jiang Y, Gao F, Lee C S, Tang J X 2019 Adv. Opt. Mater. 7 1801534
Google Scholar
[17] Fang Z, Chen W, Shi Y, Zhao J, Chu S, Zhang J, Xiao Z 2020 Adv. Funct. Mater. 30 1909754
Google Scholar
[18] Li Z, Chen Z, Yang Y, Xue Q, Yip H L, Cao Y 2019 Nat. Commun. 10 1027
Google Scholar
[19] Wang K H, Peng Y, Ge J, Jiang S, Zhu B S, Yao J, Yin Y C, Yang J N, Zhang Q, Yao H B 2018 ACS Photonics 6 667
Google Scholar
[20] Cao Y, Wang N, Tian H, Guo J, Wei Y, Chen H, Miao Y, Zou W, Pan K, He Y, Cao H, Ke Y, Xu M, Wang Y, Yang M, Du K, Fu Z, Kong D, Dai D, Jin Y, Li G, Li H, Peng Q, Wang J, Huang W 2018 Nature 562 249
Google Scholar
[21] Xu W, Hu Q, Bai S, Bao C, Miao Y, Yuan Z, Borzda T, Barker A J, Tyukalova E, Hu Z, Kawecki M, Wang H, Yan Z, Liu X, Shi X, Uvdal K, Fahlman M, Zhang W, Duchamp M, Liu J M, Petrozza A, Wang J, Liu L M, Huang W, Gao F 2019 Nat. Photonics 13 418
Google Scholar
[22] Liu Y, Cui J, Du K, Tian H, He Z, Zhou Q, Yang Z, Deng Y, Chen D, Zuo X, Ren Y, Wang L, Zhu H, Zhao B, Di D, Wang J, Friend R H, Jin Y 2019 Nat. Photonics 13 760
Google Scholar
[23] Wang Q, Wang X, Yang Z, Zhou N, Deng Y, Zhao J, Xiao X, Rudd P, Moran A, Yan Y, Huang J 2019 Nat. Commun. 10 5633
Google Scholar
[24] Kumawat N K, Dey A, Kumar A, Gopinathan S P, Narasimhan K L, Kabra D 2015 ACS Appl. Mater. Interfaces 7 13119
Google Scholar
[25] Kim H P, Kim J, Kim B S, Kim H M, Kim J, Yusoff A R b M, Jang J, Nazeeruddin M K 2017 Adv. Opt. Mater. 5 1600920
Google Scholar
[26] Wang Q, Ren J, Peng X F, Ji X X, Yang X H 2017 ACS Appl. Mater. Interfaces 9 29901
Google Scholar
[27] Vashishtha P, Ng M, Shivarudraiah S B, Halpert J E 2018 Chem. Mater. 31 83
Google Scholar
[28] Cheng L, Cao Y, Ge R, Wei Y Q, Wang N N, Wang J P, Huang W 2017 Chin. Chem. Lett. 28 29
Google Scholar
[29] 段聪聪, 程露, 殷垚, 朱琳 2019 物理学报 68 158503
Google Scholar
Duan C C, Chen L, Yin Y, Zhu L 2019 Acta Phys. Sin. 68 158503
Google Scholar
[30] Jiang Y, Qin C, Cui M, He T, Liu K, Huang Y, Luo M, Zhang L, Xu H, Li S, Wei J, Liu Z, Wang H, Kim G H, Yuan M, Chen J 2019 Nat. Commun. 10 1868
Google Scholar
[31] Ren Z, Xiao X, Ma R, Lin H, Wang K, Sun X W, Choy W C H 2019 Adv. Funct. Mater. 29 1905339
Google Scholar
[32] Zheng F, Chen W, Bu T, Ghiggino K P, Huang F, Cheng Y, Tapping P, Kee T W, Jia B, Wen X 2019 Adv. Energy Mater. 9 1901016
Google Scholar
[33] 黎振超, 陈梓铭, 邹广锐兴, 叶轩立, 曹镛 2019 物理学报 68 158505
Google Scholar
Li Z C, Chen Z M, Zou G R X, Yip H L, Cao Y 2019 Acta Phys. Sin. 68 158505
Google Scholar
[34] Li G, Tan Z K, Di D, Lai M L, Jiang L, Lim J H W, Friend R H, Greenham N C 2015 Nano Lett. 15 2640
Google Scholar
[35] Edri E, Kirmayer S, Kulbak M, Hodes G, Cahen D 2014 J. Phys. Chem. Lett. 5 429
Google Scholar
[36] Shi H, Du M H 2014 Phys. Rev. B 90 174103
Google Scholar
[37] Zou W, Li R, Zhang S, Liu Y, Wang N, Cao Y, Miao Y, Xu M, Guo Q, Di D, Zhang L, Yi C, Gao F, Friend R H, Wang J, Huang W 2018 Nat. Commun. 9 608
Google Scholar
[38] Yang Y, Zheng Y, Cao W, Titov A, Hyvonen J, Manders J R, Xue J, Holloway P H, Qian L 2015 Nat. Photonics 9 259
Google Scholar
[39] 王继飞, 林东旭, 袁永波 2019 物理学报 68 158501
Google Scholar
Wang J F, Lin D X, Yuan Y B 2019 Acta Phys. Sin. 68 158501
Google Scholar
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