Carbon perovskite solar cells (C-PSCs), using carbon-based counter electrodes (C-CEs), promise to mitigate instability issues while providing solution-processed and low-cost device configurations. In this work, we report the fabrication and characterization of efficient paintable C-PSCs obtained by depositing a low-temperature-processed graphene-based carbon paste atop prototypical mesoscopic and planar n–i–p structures. Small-area (0.09 cm 2 ) mesoscopic C-PSCs reach a power conversion efficiency (PCE) of 15.81% while showing an improved thermal stability under the ISOS-D-2 protocol compared to the reference devices based on Au CEs. The proposed graphene-based C-CEs are applied to large-area (1 cm 2 ) mesoscopic devices and low-temperature-processed planar n–i–p devices, reaching PCEs of 13.85 and 14.06%, respectively. To the best of our knowledge, these PCE values are among the highest reported for large-area C-PSCs in the absence of back-contact metallization or additional stacked conductive components or a thermally evaporated barrier layer between the charge-transporting layer and the C-CE (strategies commonly used for the record-high efficiency C-PSCs). In addition, we report a proof-of-concept of metallized miniwafer-like area C-PSCs (substrate area = 6.76 cm 2 , aperture area = 4.00 cm 2 ), reaching a PCE on active area of 13.86% and a record-high PCE on aperture area of 12.10%, proving the metallization compatibility with our C-PSCs. Monolithic wafer-like area C-PSCs can be feasible all-solution-processed configurations, more reliable than prototypical perovskite solar (mini)modules based on the serial connection of subcells, since they mitigate hysteresis-induced performance losses and hot-spot-induced irreversible material damage caused by reverse biases.

Supercapacitors (SCs), including the most established electrochemical double layer capacitors (EDLCs), are energy storage systems that can be charged in the second timescale, while sustaining a great number of re-charge cycles without losing efficiency. Undoubtedly, their major drawback is their insufficient energy density compared to batteries. Meanwhile, the reduction of the SC costs using cheap and sustainable electrolytes is also a trivial criterion to be considered in the competition race of the energy storage technologies. In this work, we report an extended characterization of aqueous SCs, screening acidic, neutral and alkaline electrolytes, as well as the addition of KI as a prototypical redox additive, and performing both two- and three-electrode configuration measurements. By using near-neutral electrolytes, our aqueous EDLCs can reach a maximum cell voltage superior to 2 V, enabling energy densities higher than 18 W h kg−1 (comparable or approaching those of lead acid and Ni–Cd batteries) at a power density up to almost 7 kW kg−1 (significantly superior to those of competing battery technologies). The introduction of redox additives can significantly increase the capacity of the SCs. However, compared to EDLCs, both the cell voltage and the energy efficiency of the SCs decrease because of partially irreversible faradaic redox reactions and overpotentials of kinetically limited redox reactions. While debunking the myth that aqueous SCs exhibit low energy density, our study also remarks the importance of adequately assessing aqueous SCs, showing the current challenges of advanced SC architectures alternative to EDLCs.

Perovskite solar cells have reached certified power conversion efficiency over 25%, enabling the realization of efficient large-area modules and even solar farms. It is therefore essential to deal with technical aspects, including the reverse-bias operation and hot-spot effects, which are crucial for the practical implementation of any photovoltaic technology. Here, we analyze the reverse bias (from 2.5 to 30 V) and temperature behavior of mesoscopic cells through infrared thermal imaging coupled with current density measurements. We show that the occurrence of local heating (hot-spots) and arc faults, caused by local shunts, must be considered during cell and module designing.