Green energy by recoverable triple-oxide mesostructured perovskite photovoltaics

Perovskite solar cells have developed into a promising branch of renewable energy. A combination of feasible manufacturing and renewable modules can offer an attractive advancement to this field. Herein, a screen-printed three-layered all-nanoparticle network was developed as a rigid framework for a perovskite active layer. This matrix enables perovskite to percolate and form a complementary photoactive network. Two porous conductive oxide layers, separated by a porous insulator, serve as a chemically stable substrate for the cells. Cells prepared using this scaffold structure demonstrated a power conversion efficiency of 11.08% with a high open-circuit voltage of 0.988 V. Being fully oxidized, the scaffold demonstrated a striking thermal and chemical stability, allowing for the removal of the perovskite while keeping the substrate intact. The application of a new perovskite in lieu of a degraded one exhibited a full regeneration of all photovoltaic performances. Exclusive recycling of the photoactive materials from solar cells paves a path for more sustainable green energy production in the future.

Elevating world temperatures along climatic model predictions (1) hasten the need for the global economy to move toward green renewable energy production. On the photovoltaic branch, organic (2), inorganic (3, 4), and photosynthetic (5) light harvesters were investigated extensively. In recent years, organic–inorganic perovskite solar cells (PSCs) have been breaking efficiency records (6). Perovskites are a widely diverse and tunable class of materials (7), possessing high charge diffusion length characteristics under illumination. The attractive qualities and surge of development have made the PSCs, especially fully printable panels (8), prominent candidates for large-scale commercialization (9). Simultaneously, much effort has been made to stabilize perovskite''s intrinsic properties (10) through the research of different compositions and fabrication methods. These efforts include the introduction of hole conductor–free configurations (11), two-dimensional perovskite compositions (12), and, recently, the usage of methylammonium-free compounds (13). In a typical PSC structure, the perovskite layer is situated between an electron-transporting layer (ETL) on the one side and a hole-transporting material (HTM) on the other side. Traditionally, a metal contact is evaporated onto the HTM as a cathode, sealing the basic functional structure of the cell. The alignment of the electronic structure of the functional layers enables the ETL to effectively block the diffusion of holes from the perovskite and the HTM to block electrons from reaching the cathode. HTM-free configurations eliminate the HTM layer between the light absorber and the cathode and rely on the ETL alone to induce anisotropic average diffusion of the charges as a photocurrent. Since HTMs are commonly expensive and prone to degradation over time, HTM-free configurations contribute to the cells'' durability and tenability and significantly lower their cost. One such configuration utilizes a porous carbon layer as the cathode of the cell (14), allowing the perovskite precursor solution to percolate through the pores and crystalize inside the structure.Here, a triple-layered structure of sintered nanoparticles (NPs) was designed as a general scaffold for various perovskite compositions and deposition methods. The rigid and stable, screen-printed oxide nanoparticle films form layers which manifest electronic attributes similar to their building blocks. The general structure of the scaffold includes a porous electron-conducting NP layer and a porous NP cathode, separated by a porous insulating NP layer. Though the use of alternative conductive NPs is plausible, indium tin oxide (ITO) particles were chosen as the cathodic material in this work. This conductive metal oxide material can endure more extreme chemical and thermal conditions than most other nanoparticles can. The virtue of such oxides lies in their strong structure and inert chemical behavior toward oxygen and water. NPs of the closely related metal oxide fluorine-doped tin oxide (FTO) are possible candidates for the substitution of ITO as the cathodic material in the future, with economic advantages appealing for commercialization. Widely used in the field of PSCs, mesoporous TiO₂ (mpTiO₂) possesses the ability to efficiently receive and conduct electrons from the conduction band of the perovskite and thus serves as the ETL in the structure. Since charge separation in PSCs arises from light absorption in the perovskite, continuity and connectivity of the perovskite material must be maintained, along with complete insulation between the anodic and cathodic parts of the cell. Screen-printed mesoporous ZrO₂ (mpZrO₂) was used here as an ideal material choice for the insulating layer. All three mentioned layers were successively printed and sintered atop a transparent FTO-coated glass photoanode to complete a full scaffold configuration of FTO/mpTiO₂/mpZrO₂/mpITO. The perovskite solution can then be applied directly onto the cathode contact, subsequently forming a three-dimensional polycrystalline network of perovskite in the cavities between the scaffold NPs. The ITO contact provides direct electron injection to the perovskite under illumination, and at this point the cell’s full structure is complete, without the need for any additional steps. Here, the deposition of (MA_0.15FA_0.85)PbI₃ perovskite is demonstrated, along with an optical, morphological, electronic, and photovoltaic characterization of the cells. These scalable solar cells exhibited high short-circuit currents, impressive stability, and the unique possibility of recycling by removing and reapplying damaged or degraded perovskite.