Improved QSS-μPCD measurement with quality of decay control: Correlation with steady-state carrier lifetime

Excess carrier photoconductance decay lifetime, measured under small perturbation conditions imposed on steady-state generation, offers an attractive and parameter free alternative to quasi-steady-state photoconductance, QSSPC. A recent version of this technique referred to as QSS-μPCD is based on microwave reflectance PCD monitoring. For this technique, it is critically important to maintain a mono-exponential decay over a large range of steady-state light intensity. Toward that goal we present QSS-μPCD with stringent quality of decay control, QDC. The quality of decay parameter, QD (ideally QD=1) measures the direction and magnitude of departures from an ideal exponential transient and enables tuning toward an optimal range of experimental variables, both apparatus and wafer dependent, whereby QD is within 1±Δ where Δ defines the QDC limits. Within QDC limits, the small perturbation effective decay lifetime, τeff.d, enables accurate determination of important silicon PV parameters, up to about 25 suns, including J0 and the steady-state lifetime, τeff.ss. Two J0 procedures are compared. The ingenious analytical procedure adopted from Basore and Hansen (1990) [2] enables direct determination of J0. The second J0 procedure uses integration of τeff.d over illumination intensity. The results are self-consistent and they show excellent correlation with Sinton QSSPC results.

► Excess carrier decay is measured with small perturbation QSS-μPCD technique. ► Novel quality of decay control eliminates problems with non-exponential decays. ► Unified measurements of decay and steady-state lifetime are reported. ► Measurements of both lifetimes are parameter-free. ► 1:1 correlation of QSS-μPCD and QSSPC results are shown for PV wafers and structures.