Progress of solution-processed metal oxides as charge transport layers towards efficient and stable perovskite solar cells and modules

Abstract

Recently, perovskite solar cells (PSCs) and perovskite solar modules (PSMs) with power conversion efficiency (PCE) over 25% and 20% have been reported, respectively. Besides developing fabrication approaches to achieve high-quality perovskite light absorbing layers, it is necessary for high-efficiency PSCs and PSMs to be equipped with high-performance charge transport layers, i.e., electron transport layers (ETLs) and hole transport layers (HTLs), which enable sufficient light transmission and effective charge extraction and transport. Metal oxides not only satisfy the requirement as high-efficiency charge transport layer, but also exhibit excellent stability against heat, light and moisture. Solution-processed method for metal oxide nanoparticles is one of the most widely used routes for the deposition of ETLs and HTLs due to its low cost, convenience and high quality. Furthermore, it is also the best choice for developing large-scale PSMs and its commercialization. In this review, some most promising metal oxides such as titanium oxide and tin oxide as ETLs and nickel oxide as HTLs, as well as its solution-processed deposition methods will be summarized. Their recent progress on interfacial passivation in small-scale PSCs and applications in large-scale PSMs will also be discussed. Finally, some challenges and perspectives on how solution-processed metal oxide materials can be developed for photovoltaic devices with higher efficiency and industrial fabrication are provided.