# Overview on Different Types of Solar Cells: An Update
###### Abstract  
Solar energy is free from noise and environmental pollution. It could be used to replace non-renewable sources such as fossil fuels, which are in limited supply and have negative environmental impacts. The first generation of solar cells was made from crystalline silicon. They were relatively efficient, however very expensive because they require a lot of energy to purify the silicon. Nowadays, the production of solar cells has been improved since the first generation (thin-film solar cells, dye-sensitized solar cells, perovskite solar cells, and organic solar cells). In this work, the development of solar cells was discussed. The advantages, limitations, challenges, and future trends of these solar cells were also reported. Lastly, this article emphasized the various practices to promote solar energy and highlighted the power conversion efficiency of the fabricated devices. solar energy; thin films; organic solar cells; crystalline silicon; dye-sensitized solar cells; power conversion efficiency; renewable energy; perovskite solar cell +
Footnote †: journal: Applied Sciences  
and smaller cations, respectively, and the anion resides at the \"X\"-site. The 3D crystal structure of ABX\({}_{3}\) consists of corner-shared BX\({}_{6}\) octahedrals and \"A\" cations occupy the cavity between them [9; 10]. Materials with perovskite structures are quite abundant in nature and can be found in an enormous number of compounds that show a wide range of physical properties, applications, and importance. Perovskite solar cells can have a conventional (regular) or an inverted PSC structure, depending on the architecture. TiO\({}_{2}\) and n-type semiconductors are used in the normal configuration, whereas p-type poly (3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS) are used in the inverted configuration. Typical mesoscopic perovskite solar cell structures consist of a glass surface with a transparent conducting oxide (TCO), such as in FTO (F:SnO\({}_{2}\)), in which an anode is deposited on the glass substrate, a dense (compact) layer of TiO\({}_{2}\) is a hole-blocking layer, and a mesoporous layer of TiO\({}_{2}\) serves as an electron-transporting layer (ETL). Moreover, a layer of the perovskite material is used for light absorption, followed by a hole-transporting layer, followed by metal contacts to complete the device's structure. This type of solar cell has an organic material with a perovskite structure in its absorbing layer, most typically a lead-metal hybrid (Methylammonium lead iodide perovskite, MAPbI3). Methylammonium lead iodide is an ambipolar semiconductor that may transmit both electrons and holes to the collecting electrodes. Because of this, perovskite solar cells can operate without a hole or electron conductor. The Spiro-OMeTAD polymer composition is the HTL material most frequently utilized in perovskite solar cells. Perovskite solar cells' superior absorption capabilities and low exciton binding energy are two of their most notable features. Light absorption is the initial physical process in solar systems. When a photon activates an active material with an energy higher than its bandgap, an exciton (electron-hole pairs) is produced. Excitons must reach the contacts after being photogenerated in the perovskite to be retrieved. The charge-transport capabilities of the perovskite play a role in this process. Compared with conventional solar cells, perovskite serves as an absorber in thin-film solar cells to offer effective transport of excitons. The remarkable PCE of these perovskite solar cells is produced by the material's outstanding charge-transport properties. They possess long charge-carrier diffusion lengths surpassing 5 m and the associated lifetimes of 1 s in both single-crystal and polycrystalline films. These diffusion lengths guarantee that the produced charge can be recovered even from thicker films that absorb the input light completely. However, the interfacial contacts with the charge extraction layer also have a role in the device's ultimate quality.