tailieunhanh - Báo cáo hóa học: " Improvement of performance of InAs quantum dot solar cell by inserting thin AlAs layers"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Improvement of performance of InAs quantum dot solar cell by inserting thin AlAs layers | Hu et al. Nanoscale Research Letters 2011 6 83 http content 6 1 83 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Improvement of performance of InAs quantum dot solar cell by inserting thin AlAs layers Dongzhi Hu1 Claiborne CO McPheeters2 Edward T Yu2 Daniel M Schaadt1 Abstract A new measure to enhance the performance of InAs quantum dot solar cell is proposed and measured. One monolayer AlAs is deposited on top of InAs quantum dots QDs in multistack solar cells. The devices were fabricated by molecular beam epitaxy. In situ annealing was intended to tune the QD density. A set of four samples were compared InAs QDs without in situ annealing with and without AlAs cap layer and InAs QDs in situ annealed with and without AlAs cap layer. Atomic force microscopy measurements show that when in situ annealing of QDs without AlAs capping layers is investigated holes and dashes are present on the device surface while capping with one monolayer AlAs improves the device surface. On unannealed samples capping the QDs with one monolayer of AlAs improves the spectral response the open-circuit voltage and the fill factor. On annealed samples capping has little effect on the spectral response but reduces the short-circuit current while increasing the open-circuit voltage the fill factor and power conversion efficiency. Introduction Group III-V compound semiconductor solar cells are the highest efficiency cells developed to date 1 due to the wide range of bandgaps that can be grown with high crystalline quality in this material system. Record efficiencies around 40 2 are achieved in triple junction cells with an InGaP InGaAs Ge structure in which lattice-matched InGaAs replaces a middle GaAs layer. Due to the three-dimensional confinement of quantum dots QDs their incorporation into the middle layer enhances the photo current of solar cells which can be further improved by forward scattering techniques 3 . The electronic .