Yao Wenlong, Fang Shuyan, Hu Ziyang, Huang Like, Liu Xiaohui, Zhang Houcheng, Zhang Jing, Zhu Yuejin
Department of Microelectronic Science and Engineering, Laboratory of Clean Energy Storage and Conversion, School of Physical Science and Technology, Ningbo Collaborative Innovation Center of Nonlinear Calamity System of Ocean and Atmosphere, Ningbo University, Ningbo, 315211, China.
School of Science and Engineering, College of Science and Technology, Ningbo University, Ningbo, 315300, China.
Small. 2022 Feb;18(8):e2105140. doi: 10.1002/smll.202105140. Epub 2021 Dec 11.
In polycrystalline perovskites, grain boundaries (GBs) that isolate grains determine the optoelectronic properties of a semiconductor, and hence affect the photovoltaic performance of a solar cell. Photocurrent and photovoltage are affected by the microscopic structure of perovskites but are difficult to quantify on the intragrain length scale and are often treated as homogeneous within the photoactive layer. Here, the nanoscale through-film and lateral photoresponse of large-grained perovskite are studied by photoconductive atomic force microscopy. Photocurrent collection along GBs relies on the formation of adjacent grains, exhibiting GB to GB heterogeneity. Regarding to the spatially correlated heterogeneity, the photovoltage of grains deduced from the photoresponse curves at specific positions is larger than that of GBs by up to 0.4 V, suggesting that the photovoltage loss mainly originates from the shunting of GBs through the whole perovskite layer. These spatial heterogeneities are alleviated by depositing a capping layer onto the perovskite layer, highlighting the role of the inserted layer between the perovskite and electrode in real solar cells. This research reveals the heterogeneity of GBs and its influence on photovoltage that actually occurs in virtual solar cells, which is crucial for optimizing perovskite-based solar cells.
在多晶钙钛矿中，隔离晶粒的晶界决定了半导体的光电特性，从而影响太阳能电池的光伏性能。光电流和光电压受钙钛矿微观结构的影响，但在晶粒内长度尺度上难以量化，并且在光活性层内通常被视为均匀的。在此，通过光电导原子力显微镜研究了大晶粒钙钛矿的纳米级穿透薄膜和横向光响应。沿晶界的光电流收集依赖于相邻晶粒的形成，表现出晶界到晶界的异质性。关于空间相关的异质性，从特定位置的光响应曲线推导出的晶粒光电压比晶界的光电压大高达0.4 V，这表明光电压损失主要源于晶界在整个钙钛矿层中的分流。通过在钙钛矿层上沉积覆盖层可减轻这些空间异质性，突出了在实际太阳能电池中钙钛矿与电极之间插入层的作用。这项研究揭示了虚拟太阳能电池中实际发生的晶界异质性及其对光电压的影响，这对于优化基于钙钛矿的太阳能电池至关重要。
