Perovskite solar cell (PSC) technology [1] [2] is very promising for the generation of solar energy. However, the main impediment toward the large-scale commercial utilization of PSCs lies in their sensitivity to moisture, with the metal top electrode being one of the primary sources of degradation [3]. As a result, the development of effective solutions to prevent metal-electrode-induced degradation is critical to enable the full potential of PSCs. To prevent device degradation, several methods are being used, including optimizing the hole transporting layer (HTL), which is crucial in device operation since it acts as a protective layer for the perovskite absorber layer against environmental influences such as humidity [4].[MB1] To address the problem, this work explores a low-temperature n-i-p device architecture on flexible substrate in which a hydrophobic carbon-based electrode deposited by blade coating replaces the conventional thermally evaporated gold top electrode. Carbon electrodes are considered as a greener alternative compared to gold counterparts, due to the low-cost of the starting material that can be easily processed using simple fabrication techniques. Moreover, they could be derived from natural sources or wastes enabling a circular route [5]. Additionally, the low-temperature carbon-based PSC devices show numerous advantages, such as the ability to integrate a planar hole transport layer (HTL), a better control over perovskite crystallization, and a good compatibility with flexible substrates, roll-to-roll fabrication by using scalable deposition techniques (e.g. screen printing, inkjet printing and doctor blade coating). However, the power conversion efficiency of carbon-based PSCs still lower than that of conventional gold-based counterparts due to the inefficient charge transport and collection and poor perovskite/carbon interfacial contact.

Throughout this work, a screening of the different hole transporting materials (HTM) is carried out aiming at finding the most promising candidate to improve the performance and stability of the Carbon-based PSCs. In doing this, copper(I) thiocyanate (CuSCN), was employed as HTL since it combines intrinsic hole-transport (p-type) characteristics with wide band gaps larger than 3.5 eV [6]. At the optimized concentration, and without using any dopants, a power conversion efficiency (PCE) of 8.4% was achieved on a 1 cm² active area device. The obtained results were compared with the performance of both HTL-free devices (as internal reference) and of gold-based devices using PTAA as HTM (as state-of-art reference).

The optimization of the HTL, allowed for the demonstration of a significant improvement in the performance of the device, which could pave the way for the large-scale commercialization of PSCs with low environmental impact and promising cost-effectiveness.