School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
ACS Appl Mater Interfaces. 2020 Nov 4;12(44):49636-49647. doi: 10.1021/acsami.0c14595. Epub 2020 Oct 20.
Hybrid organic-inorganic perovskite solar cells (HOIPs), especially CHNHPbI (MAPbI), have received tremendous attention due to their excellent power conversion efficiency (25.2%). However, two fundamental hurdles, long-term stability and lead (Pb) toxicity, prevent HOIPs from practical applications in the solar industry. To overcome these issues, compositional engineering has been used to modify cations at A- and B-sites and anions at the X-site in the general form ABX. In this work, we used the density functional theory (DFT) to incorporate Rb, Cs, and FA at the A-site to minimize the volatile nature of MA, while the highly stable Ca and Sr were mixed with the less stable Ge and Sn at the B-site to obtain a Pb-free perovskite. To further enhance the stability, we mixed the X-site anions (I/Br). Through this approach, we introduced 20 new perovskite species to the lead-free perovskite family and 7 to the lead-containing perovskite family. The molecular dynamic (MD) simulations, enthalpy formation, and tolerance and octahedral factor study confirm that all of the perovskite alloys we introduced here are as stable as pristine MAPbI. All Pb-free perovskites have suitable and direct band gaps (1.42-1.77 eV) at the Γ-point, which are highly desirable for solar cell applications. Most of our Pb-free perovskites have smaller effective masses and exciton binding energies. Finally, we show that the introduced perovskites have high absorption coefficients (10 cm) and strong absorption efficiencies (above 90%) in a wide spectral range (300-1200 nm), reinforcing their significant potential applications. This study provides a new way of searching for stable lead-free perovskites for sustainable and green energy applications.
杂化有机-无机钙钛矿太阳能电池（HOIPs），特别是 CHNHPbI（MAPbI），因其优异的功率转换效率（25.2%）而受到极大关注。然而，两个基本的障碍，长期稳定性和铅（Pb）毒性，阻止了 HOIPs 在太阳能产业中的实际应用。为了克服这些问题，人们采用组成工程来修饰 A 位和 B 位的阳离子以及 X 位的阴离子，通式为 ABX。在这项工作中，我们使用密度泛函理论（DFT）将 Rb、Cs 和 FA 掺入 A 位，以最小化 MA 的挥发性，而高度稳定的 Ca 和 Sr 与不稳定的 Ge 和 Sn 混合在 B 位，以获得无铅钙钛矿。为了进一步提高稳定性，我们混合了 X 位阴离子（I/Br）。通过这种方法，我们向无铅钙钛矿家族引入了 20 种新的钙钛矿物质，向含铅钙钛矿家族引入了 7 种。分子动力学（MD）模拟、焓形成以及容忍度和八面体因子研究证实，我们引入的所有钙钛矿合金都与原始 MAPbI 一样稳定。所有无铅钙钛矿在 Γ 点都具有合适且直接的能带隙（1.42-1.77 eV），这非常适合太阳能电池应用。我们的大多数无铅钙钛矿具有较小的有效质量和激子结合能。最后，我们表明，所引入的钙钛矿在宽光谱范围（300-1200nm）内具有高吸收系数（10cm）和强吸收效率（超过 90%），这增强了它们在太阳能电池中的应用潜力。这项研究为寻找稳定的无铅钙钛矿提供了一种新的方法，以实现可持续和绿色能源应用。
