Study of Organic Polymer/Inorganic Semiconductor Hybrid Solar Cells in Inverted Structure
Date Issued
2010
Date
2010
Author(s)
Lin, Yu-Hong
Abstract
Organic photovoltaic devices are very attractive for their advantages of flexibility, light-weight, and large-area production at a dramatically low cost. In this study, the PV2000 material is used as a photoactive layer, which has a larger relative energy difference between the HOMO level of the electron-donating polymer and the LUMO level of the electron acceptor (energy difference ~1.7 eV) as compared to the standard P3HT:PCBM system, thereby leading to a larger VOC.
The better contact in the interface is achieved by the post-annealing process, which corrects the defects between electrode and polymer layer interface. Moreover, the thermally induced morphology modification, crystallization and improved interfacial transportation, thereby leading to better charge collection and reduced series resistance. These results show that the process of post-annealing is very important for our PV2000 inverted device.
We used solution process to replace deposition to spin NiO layer on active layer. NiO layer acts as an interfacial electron-blocking layer/hole-transporting layer (EBL/HTL). Utilizing its higher LUMO (lowest unoccupied molecular orbital) could block electron leakage to anode to recombine with hole. The leakage current is reduced to improve the power conversion efficiency of inverted structure devices.
When the TiO2 nanorods are introduced, an improvement of light harvest and photocurrent is achieved due to several factors. First, the photoactive layer is thickened and the light path is increased to have more light absorption. Second, the morphology is modified to provide the photoactive layer and inorganic layer a larger contact area for efficient charge collection. Third, the TiO2 nanorods enhance the photoluminescence quenching, indicating improved electron-hole dissociation. In this way, the high PCE of 5.61% from inverted PSCs is achieved.
In the second part of this work, our investigation apply the low band gap material (ITRI P47:PC70BM) as the photoactive layer. The light harvest is improved by adjusting the thickness of photoactive layer. In addition, we introduce the solution-process NiO layer between photoactive layer and silver as an electron blocking layer, therefore, the electron is forced to move toward the ITO electrodes, increasing the selectivity of the charge carriers and the shunt resistance of the photovoltaic cell.
Subjects
organic polymer solar cell
inverted structure
post-annealing
electron blocking layer
TiO2 nanorods
low band gap
SDGs
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-99-R97943081-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):851d80bc27c49d7a531e8ed3e1bd1a38