The Application And Research Of Ga³⁺ Doped Or Electron Transport Layer Used In ZnO/Si Heterojunction Solar Cells

Such novel technology for enhancement of photovoltaic efficiency, Wide band gap semiconductor heterojunction technology, quantum dots, semiconductor doping and carrier transport layer technology and so on, are taken in account for their application prospect. In this work, we choose wide band gap semiconductor Zn O, and prepare the Zn O QDs by the Sol-Gel method. After that, by the metal ion-doped, we obtain Ga3+: Zn O. Besides, with the dispersing of nano-graphite, we can introduce electron transport layer in solar cells. We devote ourselves to study the impacts on crystalline silicon solar cells by use of Zn O QDs, Ga3+: Zn O and nano- graphite. The novel technologies mainly solve the loss mechanisms of crystalline silicon solar cells: light-trapping losses, series resistance losses, thermal / quantum losses and carrier recombination losses.1. The Zn O QDs are prepared by Sol-Gel method, and the diameter of QDs can be controlled by surfactant(PVP) and its concentrate. In this case, the size of QDs is controlled below 10 nm. The Zn O/Si heterojunction solar cells are prepared in the process of sol-gel dip-coating method and rapid annealing. The performance parameters of solar cells are improved, which due to that Zn O QDs have Strong absorption properties in ultraviolet, multiple exciton generation performance, and heterojunction is benefit to the separation of electron-hole pairs. So the power conversion efficiency improves by 7%.2. Based on Zn O QDs, we obtain the Ga3+: Zn O by metal ion-doped. Ga3+: Zn O not only retain the properties of Zn O QDs, but also decrease the resistance of Zn O. Ga3+: Zn O belongs n-type semiconductor, internal carrier density is larger than that in Zn O QDs. So, resistance is reduced. We study the performances of Ga3+: Zn O/Si heterojunction solar cells by various concentrate of Ga3+. The performances of Ga3+: Zn O/Si heterojunction solar cells improve in different degrees. Compare with the Zn O/Si heterojunction solar cells, the power conversion efficiency improves by 5.65%.3. The main role of the electron transport layer is transport and collection photo-generated carriers. Since the direction of electron transport in heterojunction is quasi-two-dimensional(the heterojunction interface parallel). The transport and collection of photo-generated electron are affected. We choose the nano-graphite(Φ≈30nm) as the electron transport layer. The electron mobility increases obviously, which due to that the graphite is conductor and the increasing of carrier density is leading to the ionized impurity scattering and piezoelectric scattering which play great roles in electron mobility are shielded efficiently. So, the power conversion efficiency improves. Compare with the Zn O/Si heterojunction solar cells and Ga3+: Zn O/Si heterojunction solar cells, PCE increases by 10.1% and 4.2% respectively.