Comparison of the device physics principles of planar and radial p-n junction nanorod solar cells

A device physics model has been developed for radial p-n junction nanorod solar cells, in which densely packed nanorods, each having a p-n junction in the radial direction, are oriented with the rod axis parallel to the incident light direction. High-aspect-ratio (length/diameter) nanorods allow the use of a sufficient thickness of material to obtain good optical absorption while simultaneously providing short collection lengths for excited carriers in a direction normal to the light absorption. The short collection lengths facilitate the efficient collection of photogenerated carriers in materials with low minority-carrier diffusion lengths. The modeling indicates that the design of the radial p-n junction nanorod device should provide large improvements in efficiency relative to a conventional planar geometry p-n junction solar cell, provided that two conditions are satisfied: (1) In a planar solar cell made from the same absorber material, the diffusion length of minority carriers must be too low to allow for extraction of most of the light-generated carriers in the absorber thickness needed to obtain full light absorption. (2) The rate of carrier recombination in the depletion region must not be too large (for silicon this means that the carrier lifetimes in the depletion region must be longer than ~10 ns). If only condition (1) is satisfied, the modeling indicates that the radial cell design will offer only modest improvements in efficiency relative to a conventional planar cell design. Application to Si and GaAs nanorod solar cells is also discussed in detail.

[1]  A. Blakers,et al.  A novel low-cost, high-efficiency micromachined silicon solar cell , 2004, IEEE Electron Device Letters.

[2]  M. Green,et al.  Novel parallel multijunction solar cell , 1994 .

[3]  Stephen J. Fonash,et al.  太阳电池器件物理 = Solar cell device physics , 1982 .

[4]  Charles M. Lieber,et al.  Epitaxial core–shell and core–multishell nanowire heterostructures , 2002, Nature.

[5]  Arun Majumdar,et al.  Design of Nanostructured Heterojunction Polymer Photovoltaic Devices , 2003 .

[6]  Masafumi Yamaguchi,et al.  Effect of grain size and dislocation density on the performance of thin film polycrystalline silicon solar cells , 1997 .

[7]  S. Fonash.  Physics and Materials Properties Basic to Photovoltaic Energy Conversion , 1981 .

[8]  Peidong Yang,et al.  Block-by-Block Growth of Single-Crystalline Si/SiGe Superlattice Nanowires , 2002 .

[9]  E. Palik.  Handbook of Optical Constants of Solids , 1997 .

[10]  R. Pierret,et al.  Advanced semiconductor fundamentals , 1987 .

[11]  Charles M. Lieber,et al.  Growth of nanowire superlattice structures for nanoscale photonics and electronics , 2002, Nature.

[12]  Richard K. Ahrenkiel,et al.  Auger recombination in heavily carbon-doped GaAs , 2001 .

[13]  Kenji Hiruma,et al.  GaAs p‐n junction formed in quantum wire crystals , 1992 .

[14]  Heon-Jin Choi,et al.  Single-crystal gallium nitride nanotubes , 2003, Nature.

[15]  W. Read,et al.  Statistics of the Recombinations of Holes and Electrons , 1952 .

[16]  Uwe Rau,et al.  Modeling extremely thin absorber solar cells for optimized design , 2004 .

[17]  V. Schlosser.  Limiting factors for the application of crystalline upgraded metallurgical grade silicon , 1984, IEEE Transactions on Electron Devices.

[18]  C. Sah,et al.  Carrier Generation and Recombination in P-N Junctions and P-N Junction Characteristics , 1957, Proceedings of the IRE.

[19]  Lars Samuelson,et al.  One-dimensional steeplechase for electrons realized , 2002 .