Battula Ramya Krishna, Veerappan Ganapathy, Bhyrappa P, Sudakar C, Ramasamy Easwaramoorthi
Centre for Solar Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) Hyderabad 500005 India
Department of Chemistry, Indian Institute of Technology Madras Chennai 600036 India.
RSC Adv. 2020 Aug 20;10(51):30767-30775. doi: 10.1039/d0ra05590e. eCollection 2020 Aug 17.
Single crystalline perovskite solar cells (PSC) are promising for their inherent stability due to the absence of grain boundaries. While the development of single crystals of perovskite with enhanced optoelectronic properties is known, studies on the growth, device performance and understanding of the intrinsic stability of single crystalline perovskite thin film solar cell devices fabricated on electron selective contacts are scarcely explored. In this work, we examine the impact of mesoporous TiO (m-TiO) and planar TiO (p-TiO) on the growth of single crystalline-methyl ammonium lead iodide (SC-MAPbI) film, PSC device performance and film stability under harsh weather conditions (T ∼ 85 °C and RH ∼ 85%). Self-grown SC-MAPbI films are developed on m-TiO and p-TiO by inverse temperature crystallization under ambient conditions without the need for sophisticated glove-box processing. The best device with m-TiO as an electron transport layer showed a promising power conversion efficiency of 3.2% on an active area of 0.3 cm in hole transport material free configuration, whereas, only 0.7% was achieved for the films developed on p-TiO. Complete conversion of precursor to perovskite phase and better surface coverage of the film leading to enhanced absorption and reduced defects of single crystalline perovskite on m-TiO compared to its p-TiO leads to this large difference in efficiency. Mesoporous device retained more than 70% of its initial performance when stored at 30 °C under dark for more than 5000 h at 50% RH; while the planar device degraded after 1500 h. Thermal and moisture endurance of SC-MAPbI films are investigated by subjecting them to temperatures ranging from 35 °C to 85 °C at a constant relative humidity (RH) of 85%. X-ray diffraction studies show that the SC-MAPbI films are stable even at 85 °C and 85% RH, with only slight detection (30-35%) of PbI at these conditions. This study highlights the superior stability of SC-MAPbI films which paves way for further studies on improving the stability and performance of the ambient processed PSCs.
单晶钙钛矿太阳能电池（PSC）因其不存在晶界而具有内在稳定性，因而颇具前景。虽然人们已知如何开发具有增强光电性能的钙钛矿单晶，但对于在电子选择性接触上制备的单晶钙钛矿薄膜太阳能电池器件的生长、器件性能以及内在稳定性的理解方面的研究却鲜有涉及。在这项工作中，我们研究了介孔TiO（m-TiO）和平面TiO（p-TiO）对单晶甲基铵碘化铅（SC-MAPbI）薄膜生长、PSC器件性能以及在恶劣天气条件（温度约85°C，相对湿度约85%）下薄膜稳定性的影响。在环境条件下，通过逆温结晶在m-TiO和p-TiO上制备出自生长的SC-MAPbI薄膜，无需复杂的手套箱处理。以m-TiO作为电子传输层的最佳器件在无空穴传输材料的配置下，在0.3平方厘米的有源面积上展现出了3.2%的可观功率转换效率，而在p-TiO上制备的薄膜仅实现了0.7%的效率。与p-TiO相比，前驱体向钙钛矿相的完全转化以及薄膜更好的表面覆盖率，使得单晶钙钛矿在m-TiO上的吸收增强且缺陷减少，从而导致了这种效率上的巨大差异。介孔器件在50%相对湿度下于30°C黑暗中储存超过5000小时后，仍保留了其初始性能的70%以上；而平面器件在1500小时后性能下降。通过在85%的恒定相对湿度下将SC-MAPbI薄膜置于35°C至85°C的温度范围内，研究了其耐热性和耐湿性。X射线衍射研究表明，SC-MAPbI薄膜即使在85°C和85%相对湿度下也很稳定，在这些条件下仅能轻微检测到（30 - 35%）PbI。这项研究突出了SC-MAPbI薄膜的卓越稳定性，为进一步研究提高环境处理PSC的稳定性和性能铺平了道路。
