Perovskite solar cells, using methylamine lead iodide material as the heart of the solar cell, shows a great potential for next generation of low-cost and efficient photovoltaic cells. Although high efficiency PV solar cells using silicon and also compound semiconductors have already been commercialized, the manufacturing procedures are still costly regarding to materials and methods. Furthermore, cheap and efficient organic and dye-sensitized solar cells (DSSCs) have made a satisfactory progress recently, however their highest efficiency and performance is fallen behind their inorganic thin-film cousins. Therefore, substantial progress in the field of solution-processable solar cells has been driven by the preparation of novel electron-donor materials for OPVs (organic photovoltaic) devices, and the synthesis of new redox and dyes mediators for DSSCs. In recent decades, organic/inorganic hybrid perovskite materials were introduced as an exciting and novel alternative to be used as light-absorbing component in traditional solar cell device architectures such as DSSC (mesoscopic) structure or thin film devices (planar perovskite solar cells (PSCs)). Their remarkably rapid advancements starting from a maximum efficiency of 3.8% in a DSSC structure, suggest that solar cells with device efficiency more than 22% are realistically achievable in only 7 years. However, further enhancement of the solar cell efficiency and specially stability is needed for practical applications. Early work perovskite solar cells based on a photo anode (e.g. mesoporous TiO2 scaffold), a light-absorbing perovskite component (e.g. CH3NH3PbI3 with light absorption coefficient more than 104 cm-1 and bandgap from 1.5 eV to 2.3 eV), and a hole-transport layer (e.g. spiro-OMeTAD) has achieved excellent device efficiency. Recently, 3D organic/inorganic hybrid perovskites, because of their exceptional optical and electrical characteristics, with their great flexibility for constructing interesting quantum confinement structures, have employed in thin film solar cells, affording an desirable alternative for solar energy usage.
|Figure: Schematic of a sensitized perovskite solar cell in which the active layer consist of a layer of mesoporous TiO2 which is coated with the perovskite absorber. The active layer is contacted with an n-type material for electron extraction and a p-type material for hole extraction. b) Schematic of a thin-film perovskite solar cell. In this architecture in which just a flat layer of perovskite is sandwiched between two selective contacts. c) Charge generation and extraction in the sensitized architecture. After light absorption in the perovskite absorber the photogenerated electron is injected into the mesoporous TiO2 through which it is extracted. The concomitantly generated hole is transferred to the p-type material. d) Charge generation and extraction in the thin-film architecture. After light absorption both charge generation as well as charge extraction occurs in the perovskite layer (Figure and caption used with permeation from here).|
In order to prepare the hybrid perovskite film, there are several different techniques, such as vacuum vapor deposition, One-step deposition method, two-step deposition technique (TSD), vapor-assisted solution method, and other techniques. The traditional technique to produce the solar cells is solution based spin-coating method, yet it is not easy to control film characteristics like thickness, uniformity, and also morphology. In the recent reports of successful perovskite solar cells, the perovskite material normally combined with mesoporous TiO2 as cathode material contacted to a conductive glass such as FTO or ITO coated glass. Although, in some interesting reports Al2O3 or ZrO2 (as electron blocker) or ZnO are used in mesoporous form or thin dense film; but, still fabrication of these kind of solar cell by using of mesoporous TiO2 layers absorb interest of many research groups.
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