Passiviation of L-3-(4-Pyridyl)-alanine on Interfacial Defects of Perovskite Solar Cell

A Synergistic Effect among Multiple Functional Groups of 4‐PyAO Additive for Performance Enhancement of Tin‐Based Perovskite Solar Cells

“…The defect state density can be calculated according to the voltage value ( V TFL ) at the point where the Ohmic region becomes the trap‐filling limited region. [ 48 ] The V TFL of the device with 4‐PyAO was smaller than that of the control (Figure 5d), and consequently, the estimated defect state density decreased from 7.75 × 10 15 to 7.10 × 10 15 cm −3 (Figure 5e). The results quantitatively demonstrate the decreased trap states induced by 4‐PyAO addition.…”

Rational Selection of the Lewis Base Molecules Targeted for Lead-Based Defects of Perovskite Solar Cells: The Synergetic Co-passivation of Carbonyl and Carboxyl Groups

“…Among the various defects, Pb-based defects such as uncoordinated Pb 2+ , metallic lead (Pb 0 ), Pb–I antisite, and lead clusters are easily formed and contribute to the major deep energy level defects. − For example, during the thermal annealing process, organic volatile components tend to escape from the perovskite, leaving uncoordinated Pb 2+ defects due to their low formation energy, and Pb 2+ may be reduced to Pb 0 during film preparation or device operation. These Pb-based defects are chiefly responsible for the loss of Shokley–Read–Hall (SRH) nonradiative recombination energy at the interface between the perovskite and hole transport layer (HTL), which are considered to be one of the most detrimental intrinsic factors for the deterioration of the PCE and stability of PSCs. − To minimize the detrimental effect of Pb-based defects, many passivation agents have been developed, such as polymers, organic ammonium salts, inorganic salts, and Lewis acids and bases. ,− In particular, defect passivation through Lewis acid–base chemistry has recently attracted significant interest because of its unique advantages and proven ability to improve the PCE and stability of PSCs. − Among various Lewis acid–base additives, Lewis base molecules containing CO bonds have been extensively studied due to their high stability and solid interaction with perovskites. ,− For example, in our recent work, three prototypical low-cost polymers, namely, poly­(vinyl acetate) (PVA), polyethylene glycol (PEG), and poly­(9-vinylcarbazole) (PVK), were adopted to investigate the effects of the molecular structure of polymeric passivating agents on the effectiveness of surface defect passivation. It was demonstrated that PVA with minimized steric hindrance and the strongest CO functional group demonstrated the best defect passivation effect and the most enhanced carrier diffusion ability, resulting in a PCE of 23.20% and significantly enhanced operational stability .…”

Performance of Perovskite solar cells Doped with L-arginine

“…随着能源问题日趋严峻，太阳电池研究备受关 注。目前最常见的太阳电池是晶硅太阳电池，但高 纯硅成本高、提纯复杂，限制了其进一步的发展。 自 2009 年钙钛矿材料作为敏化剂首次引入染料敏 化太阳电池实现了 3.8%的光电效率(PCE) [1] 至今， 其 PCE 已经提升至 25.6% [2] 。有机-无机杂化钙钛矿 材料具有高吸光系数 [3] 、低激子结合能 [4] 等优点， 以其作为光吸收层材料的钙钛矿太阳电池(PSCs)凭 借带隙可调 [5] 、PCE 高 [6] 等优点成为了当前新能源 材料领域的研究热点。 尽管 PSCs 具有诸多优点， 但仍存在稳定性低 [7] 、 迟滞效应显著 [8][9] 等缺点，制约了其商业化进程，这 与钙钛矿材料中存在的缺陷密不可分 [9] 。实际的钙 钛矿材料晶体并非完全呈周期性排列，而是存在晶 格失配 [10] 、晶界 [11] 、离子空位 [12] 等缺陷，这些缺陷 通过影响载流子正常输运影响了 PSCs 的 PCE 等性 能，例如深能级缺陷作为陷阱会增加载流子的非辐 射复合，缩短载流子寿命和降低开路电压 [13] ，进而 影响 PSCs 器件性能。有研究表明，在钙钛矿材料 中引入有机小分子物质可以有效钝化钙钛矿材料缺 陷 [14][15] ，而现有研究中官能团常为单个作用，多个 官能团作用的报道相对较少。掺杂多官能团的材料 不仅会为 PSCs 带来更优的缺陷钝化效果，还可钝 化界面处的缺陷 [16] 。王照奎等 [17] 通过掺杂茶碱、 咖啡因和可可碱发现了 NH 与 C=O 基团的协同钝化 作用；黄劲松课题组 [18] 发现羧基可通过静电相互作 用修复带电缺陷；杨阳等 [19] 通过在钙钛矿中掺杂尿 素(含 C=O、NH2)，有效增大了晶粒尺寸并提高了 钙钛矿材料 MAPbI3 的结晶活化能，使得结晶活动 放缓、结晶度提升，从而提升了 PSCs 光电性能。 用以调整因缺陷而畸变的钙钛矿晶格 [17] ，从而降低 了有害缺陷的影响。 半导体辐射复合指载流子直接通过导带与价带 复合，或通过复合中心进行间接复合；非辐射复合 [25] 指有声子参与的复合，如俄歇复合和多声子复合。 非辐射复合会对器件的载流子输运产生不利影响 [26] 。因此对钙钛矿薄膜进行了 PL 和 TRPL 表征， 如图 4(a)所示，掺杂后薄膜的 PL 荧光强度增强，…”

“…其中，q=1.602×10 −19 C，N 表示缺陷密度(cm −3 )，L 为钙钛矿层厚度(nm)，ε 为钙钛矿的相对介电常数 (46.9)，ε0 是真空介电常数(8.8542×10 −14 F• cm −1 )。对 SCLC 曲线双坐标轴取对数拟合后分成三个区域， 分别为欧姆区(Omhic)、缺陷填充限制区(TFL)和子 区(Child)，Omhic 和 TFL 区交界处对应为缺陷填充 极限电压(VTFL) [30] ，通过计算可以发现缺陷密度随 着 L-精氨酸掺杂由 4.8310 16 [31] ，这也验证了 上述测试结果的可靠性。未配位的 Pb 2+ 与 Lewis 碱 分子发生配位结合， 同时 L-精氨酸中的 N-H 和 C=O 对钙钛矿材料起到协同钝化作用，即 L-精氨酸的 NH 和卤素离子之间的氢键同时 C=O 与 PbI 反位铅 缺陷结合 [17] ，从而起到钝化 PbI 型缺陷的作用。…”