A facile spray deposition process was developed to prepare high-quality perovskite films with full surface coverage and large grain size.

The process of crystallization of lead halide perovskites by industrially relevant techniques involving non-toxic solvents is not understood completely and needs improvement. To this date, devices with the highest efficiency are prepared by deposition of the perovskite layer using non-scalable techniques, toxic solvents and/or require additional processing steps. In this work, we show that perovskite solar cells can be obtained efficiently in one step by doctor blade. The perovskite film is formed under a supersaturation regime from non-toxic solvents following spherulitic growth. This method results in highly crystalline perovskite films with preferential crystal orientation. Co-local photoluminescence and light-beam induced current experiments show that the generated chemical defects are confined at the boundary of spherulites and do not have a negative effect on the extracted photocurrent. Strikingly, spherulite formation, rather than being detrimental, could lead to better photovoltaic performance in hybrid perovskite films. This is further confirmed in the photovoltaic devices, which were fabricated using non-toxic solvents by doctor blade process, with record efficiencies of 18.0% for MAPbI₃ (MA = methyl ammonium). Moreover, devices with large area (1.53 cm²) fabricated using doctor blade show remarkable efficiencies (14.2%) reinforcing the viability of this solar technology towards industrialization.

Hybrid perovskites are promising materials for new sustainable photovoltaic applications to operate under low lighting conditions, such as the reuse of residual photons that are wasted during indoor lighting. The requirements for a perovskite solar cell (PSC) to offer maximum power conversion efficiency (PCE) under low illumination conditions are not totally clear in the literature. In this work, the PCE of the commonly used SnO₂ electron transport layer (ETL) is improved by a facile method, doping the precursor nanoparticles with small concentrations of a Pb source. Under low illumination conditions (i.e., 0.1 mW cm⁻²) the PCE is enhanced from 18.8% to 34.2%. From a complete analysis of the ETLs and devices using several structural and electrical techniques it is observed that the parameter that improves the most is the shunt resistance of the device which avoids the parallel leakage of the photogenerated current. The present work clearly shows that the shunt resistance is a very important parameter that needs to be optimized in PSCs for low illumination conditions.

Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate. CdS and CdSe colloidal quantum dots are assembled onto ZnO nanorods array using water-soluble nanocrystals capped as-synthesized with a short-chain bifuncional linker thioglycolic acid. The solar cells co-sensitized with both CdS and CdSe quantum dots demonstrate superior efficiency compared with the cells using only one type of quantum dots. A thin Al₂O₃ layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55. The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage.