Thakur Sandip, Dai Zhenghong, Karna Pravin, Padture Nitin P, Giri Ashutosh
Department of Mechanical, Industrial and Systems Engineering, University of Rhode Island, Kingston, RI, 02881, USA.
School of Engineering, Brown University, Providence, Rhode Island, 02912, USA.
Mater Horiz. 2022 Nov 28;9(12):3087-3094. doi: 10.1039/d2mh01070d.
Proper thermal management of solar cells based on metal halide perovskites (MHPs) is key to increasing their efficiency as well as their durability. Although two-dimensional (2D) MHPs possess enhanced thermal stability as compared to their three-dimensional (3D) counterparts, the lack of comprehensive knowledge of the heat transfer mechanisms dictating their ultralow thermal conductivities is a bottleneck for further improvements in their thermal performance. Here, we experimentally and computationally study the Dion-Jacobson (DJ) and Ruddlesden-Popper (RP) phases of MHPs ( = 1) to demonstrate that the length of the organic spacers has a negligible influence on their thermal transport properties; we experimentally measure thermal conductivities of 0.19 ± 0.03 W m K and 0.18 ± 0.03 W m K for the RP and DJ phases with 13.6 Å and 6.3 Å interlayer inorganic separations, respectively. In contrast, we show that thermal conductivity is mainly dependent on the separation between the adjacent organic cations. Decreasing the intermolecular distance (by up to 40%) leads to drastically enhanced overall heat conduction (with monotonically increasing thermal conductivity by more than threefold) which is mainly driven by the vibrational hardening of the organic spacers. Although these 2D layered materials constitute a high density of hybrid organic-inorganic interfaces, our results also show that a substantial portion of heat is conducted through coherent phonon transport and that the thermal conductivity of these materials is not solely limited by incoherent interfacial scattering.
对基于金属卤化物钙钛矿（MHP）的太阳能电池进行适当的热管理是提高其效率和耐久性的关键。尽管二维（2D）MHP与其三维（3D）对应物相比具有更高的热稳定性，但缺乏对决定其超低热导率的传热机制的全面了解是进一步提高其热性能的瓶颈。在此，我们通过实验和计算研究了MHP（ = 1）的狄翁 - 雅各布森（DJ）相和拉德勒斯登 - 波普尔（RP）相，以证明有机间隔基的长度对其热传输特性的影响可忽略不计；我们分别测量了层间无机间距为13.6 Å和6.3 Å的RP相和DJ相的热导率，分别为0.19±0.03 W m K和0.18±0.03 W m K。相比之下，我们表明热导率主要取决于相邻有机阳离子之间的间距。减小分子间距离（最多可达40%）会导致整体热传导大幅增强（热导率单调增加超过三倍），这主要是由有机间隔基的振动硬化驱动的。尽管这些二维层状材料构成了高密度的有机 - 无机混合界面，但我们的结果还表明，相当一部分热量是通过相干声子传输进行传导的，并且这些材料的热导率并不完全受非相干界面散射的限制。
