Fernando Núñez-Gálvez, Xabier García-Casas, Lidia Contreras Bernal, Alejandro Descalzo, José Manuel Obrero-Pérez, Juan Pedro Espinós, Ángel Barranco, Ana Borras, Juan Ramón Sánchez-Valencia, Carmen López-Santos
arXiv:2407.07581
DOI: 10.48550/arXiv.2407.07581
The hybrid configuration of energy harvesting systems is a promising avenue in the quest for clean and affordable energy. Recent results in the literature have proven the advantages of combining drop energy harvesting triboelectric nanogenerators (D-TENG) with photovoltaic cells to demonstrate compatible solar and rain panels working under all environmental conditions. The stability and reproducibility issues related to metal halide Perovskite Solar Cells (PSCs) have prevented so far from exploiting this highly efficient photovoltaic technology under rainy or even moisture conditions. Protecting the PSCs with a waterproof encapsulator could overcome such a disadvantage. However, typical commercial resin-type encapsulants are incompatible with the most popular hole transport materials, i.e., Spiro-OMeTAD layers. Herein, we propose the implementation of fluorinated carbon (CFx) coatings produced by Plasma-Enhanced Chemical Vapor Deposition (PECVD) as a two-fold encapsulating layer, enabling waterproof capability for the PSC and working as an energy harvesting surface for a triboelectric-based drop energy nanogenerator. These conformal thin films with thickness in the range of 100 nm present a compact microstructure and optimal optical transmittance (above 90%), allowing for a complete preservation of the photovoltaic parameters of the cell. The improved long-term stability of the water-resistant PSCs prevents degradation under illumination in outdoor or simulated adverse environments with high humidity, high temperature, water immersion, or rain. As a remarkable result, the 50% Power Conversion Efficiency (PCE) has been retained after ten days of illumination under 100% relative humidity at 50 ºC. Also, the CFx coatings were successfully tested as a promoter agent to integrate commercial UV-curable sealants compatible with Spiro-OMeTAD, enhancing the performance stability of up to 80% of PCE after 100 hours under illumination in a humid environment. This water-resistant PSC was tested in a top-bottom electrode configuration for harvesting kinetic energy from droplets with different compositions (milli-Q, rain, and salty water) sharing the transparent conducting electrode of the PSC as the bottom electrode and a thin gold exposed electrode deposited on top of the CFx encapsulant. Devices were compatible with simultaneously working as D-TENG and photovoltaic cells, yielding outstanding voltage outputs up to 12 V with maximum peak power density reaching 2.75 µW/cm2 as defined by the D-TENG and PCE of 11.5 % and 8.46 mA/cm2 of short circuit current determined by the PSC under dripping and for an illumination angle of 45º. The durability of the multisource device was tested under constant illumination and periodical drop impacting for more than 5 hours.