Conventional manufacturing processes of solar cells, including epitaxy, diffusion, deposition and dry etching, are
high cost and high power consumption. To save energy and reduce expenses, we use organic material, silicon
nanostructure and solution process. The devices structure is n-type bulk Si (n-Si)/n-type silicon nanowires (n-
SiNWs)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) heterostructure. The active region
includes n-Si and n-SiNW arrays, promising the property of ultra low reflection for high light absorption. In this work,
SiNWs of only a-few hundred nanometers could lower the reflectance to below 5%. In addition, an organic material -
PEDOT:PSS, instead of p-type doping, is introduced to form a p-n junction with n-Si/n-SiNWs for separating the
electron-hole pairs. The use of PEDOT:PSS can also passivate the surface defects of n-SiNWs.
N-type SiNW arrays are made by aqueous etching process. The etchant contains Ag+ and HF etching vertically to
the 1-10 Ω-cm Si (100) wafers. After etching and removing residual Ag and SiO2 by nitric acid and diluted HF
successively, n-SiNW arrays existed on either surfaces of n-Si with very dark color; then Ti and Ag were evaporated on
n-Si to be a cathode. Finally, nanowires of n-Si/n-SiNWs were stuck on the PEDOT:PSS that were spin-coated on the
ITO coated glass to form a core-sheath heterojunction.
The performance and quantum efficiencies (QE) were measured. The short circuit current density and power
conversion efficiency are 27.46 mA/cm2 and 8.05%, respectively, which are higher than other solar cells containing
SiNWs. The external and internal QE are beyond 50% and 60% in visible range, respectively.