Analysis of the photo voltage decay (PVD) method for measuring minority carrier lifetimes in P-N junction solar cells

Journal Article · Tue Sep 01 04:00:00 EDT 1981 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.329478· OSTI ID:6051479

von Roos, O

When the diffusion length of minority carriers becomes comparable or even larger than the thickness of a P-N junction solar cell, the characteristic decay of the photogenerated voltage becomes a mixture of contributions with different time constants. The minority carrier recombination lifetime tau and the time constant l/sup 2//D, where l is essentially the thickness of the cell and D the minority carrier diffusion length, determine the signal as a function of time. It is shown that for ordinary solar cells (N/sup +/-P junctions), particularly when the diffusion length L of the minority carriers is larger than the cell thickness l, the excess carrier density decays according to exp(-t/tau-..pi../sup 2/Dt/4l/sup 2/), tau being the lifetime. Therefore, tau can be readily determined by the photo voltage decay (PVD) method once D and l are known. For ideal back-surface-field (BSF) cells (N/sup +/-P-P/sup +/ junctions) under the same circumstances the excess number density of carriers decays purely exponentially as exp(-t/tau). However most BSF solar cells are not ideal, possessing an effective surface recombination velocity s/sub eff/ of 100 to 1000 cm/sec at the high-low junction. Therefore, PVD measurements for BSF cells must be treated with caution and must be supplemented with other nonstationary methods recently developed. These facts are important for a determination of diffusion lengths since steady-state methods are notoriously unreliable when the cell thickness is smaller than the diffusion length. Finally a connection will be made with older work on the same subject.

• Research Organization: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
• OSTI ID: 6051479
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 52:9; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
CHARGE CARRIERS
DATA
DECAY
DIFFUSION LENGTH
DIMENSIONS
DIRECT ENERGY CONVERTERS
EQUIPMENT
INFORMATION
JUNCTIONS
LENGTH
LIFETIME
MATHEMATICAL MODELS
NUMERICAL DATA
P-N JUNCTIONS
PHOTOELECTRIC CELLS
PHOTOELECTROMAGNETIC EFFECTS
PHOTOVOLTAIC CELLS
PHOTOVOLTAIC EFFECT
RECOMBINATION
SEMICONDUCTOR JUNCTIONS
SOLAR CELLS
SOLAR EQUIPMENT
THEORETICAL DATA
THICKNESS
TIME DEPENDENCE