High Performance Nanostructured Silicon-Organic Quasi p-n Junction Solar Cells via Low-Temperature Deposited Hole and Electron Selective Layer

Silicon-organic solar cells based on conjugated polymers such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on n type silicon (n-Si) attract wide interest because of their potential for cost-effectiveness and high-efficiency. However, a lower barrier height Phi(b) and a shallow built in potential (V-bi) of Schottky junction between n-Si and PEDOT:PSS hinders the power conversion efficiency (PCE) in comparison with those of traditional p-n junction. Here, a strong inversion layer was formed on n Si surface by inserting a layer of 1, 4, 5, 8, 9, 11-hexaazatriphenylene hexacarbonitrile (HAT-CN), resulting in a quasi p-n junction. External quantum efficiency spectra, capacitance-voltage, transient photovoltage decay and minority charge carriers life mapping measurements indicated that a quasi p-n junction was built due to the strong inversion effect, resulting in a high Phi(b) and V-bi. The quasi p-n junction located on the front surface region of silicon substrates improved the short wavelength light conversion into photocurrent. In addition, a derivative perylene diimide (PDIN) layer between rear side of silicon and aluminum cathodes was used to block the holes from flowing to cathodes. As a result, the device with PDIN layer also improved photoresponse at longer wavelength. A champion PCE of 14.14% was achieved for the nanostructured silicon-organic device by combining HAT-CN and PDIN layers. The low temperature and simple device structure with quasi p-n junction promises cost-effective high performance photovoltaic techniques.