The bulk anomalous photovoltaic (BAPV) effect of acentric materials refers to a distinct concept from traditional semiconductor-based devices, of which the above-bandgap photovoltage hints at a promise for solar-energy conversion. However, it is still a challenge to exploit new BAPV-active systems due to the lacking of knowledge on the structural origin of this concept. BAPV effects in single crystals of a 2D lead-free double perovskite, (BBA)₂CsAgBiBr₇ (1, BBA = 4-bromobenzylammonium), tailored by mixing aromatic and alkali cations in the confined architecture to form electric polarization are acquired here. Strikingly, BAPV effects manifested by above-bandgap photovoltage (V_OC) show unique attributes of directional anisotropy and positive dependence on electrode spacing. The driving source stems from orientations of the polar aromatic spacer and Cs⁺ ion drift, being different from the known built-in asymmetry photovoltaic heterojunctions. As the first demonstration of the BAPV effect in the double perovskites, the results will enrich the family of environmentally green BAPV-active candidates and further facilitate their new optoelectronic application.

中文翻译：

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在含芳碱混合阳离子的无铅双钙钛矿单晶中获得体反常光伏效应

非中心材料的体反常光伏 (BAPV) 效应指的是与传统半导体器件不同的概念，其中带隙以上的光电压暗示了太阳能转换的前景。然而，由于缺乏关于这一概念的结构起源的知识，开发新的 BAPV 主动系统仍然是一个挑战。此处获取了二维无铅双钙钛矿 (BBA) ₂ CsAgBiBr ₇ ( 1, BBA = 4-溴苄基铵) 单晶中的 BAPV 效应，该效应通过在受限结构中混合芳香族和碱金属阳离子以形成电极化而定制。引人注目的是，BAPV 效应表现为带隙以上的光电压 ( V _OC) 显示方向各向异性和对电极间距的正依赖性的独特属性。驱动源源于极性芳族间隔物的取向和 Cs ⁺离子漂移，不同于已知的内置不对称光伏异质结。作为双钙钛矿中 BAPV 效应的首次证明，该结果将丰富环境绿色 BAPV 活性候选物家族，并进一步促进其新的光电应用。