Inorganic–organic lead halide perovskite crystals possess a superior light absorption capability and tuneable bandgap, which render them promising for use in organic semiconductors, photo-detectors, and photovoltaics. The goal of using methylammonium lead iodide perovskite (MAPbI3) as a light harvester for organic photovoltaics began in 2009, when Miyasaka et al. fabricated the first MAPbX3 (X = Br or I)-sensitized solar cells by using a liquid electrolyte. However, liquid electrolytes are corrosive against perovskite crystals and were replaced by solid-state hole conductors which improve power conversion efficiency (PCE) and device stability. To date, a certified PCE of perovskite solar cells (PSCs) exceeding 20% has been achieved.
Our interest in PSC includes:
1. Electrodeposited TiO2 blocking layer:
Electrodeposition(ED) is a bottom-up methodology that provides a contour-chasing capability because the electrochemical reaction occurs on the electrode surface. In contrast to other bottom-up methods such as ALD, ED is a simple, cost-effective, and scalable method to obtain a continuous and uniform surface coating without the need for a high temperature treatment or vacuum environment. Moreover, by manipulating the parameters of ED, both film thickness and morphology can be easily controlled. TiO2 blocking layer can be formed through the fast hydrolysis of Ti3+ in an acid solution followed by a galvanic reaction, resulting in a perfectly covered TiO2 layer.
2. Lead nitrate precursor system:
We address concerns regarding the processing solvent used during perovskite deposition. Compared with lead perovskite, the pathology of which is uncertain, DMF is a toxicant and has been linked to liver disease clinically. Herein, we attempt to fabricate highly efficient PSCs using a water-based lead-precursor and lead nitrate (Pb(NO3)2), via sequential deposition. The Pb(NO3)2/water system is an alternative system that can be used in PSCs without the need for toxic solvents.
3. Lead free system:
Despite of the extremely high power conversion efficiency of methylammonium lead iodide (MAPbI3) perovskite solar cell (>20%), the toxicity of lead is a critical issue that restricts the further progress toward practical application. Taking into account the environmental concern, lead-free perovskite is a seminal strategy for future industrial development. Therefore, We endeavor to tin-based perovskite and try to overcome its intrinsic instability in ambient condition.
(CsSnI3 formed with different concentration of SnF2)