Statistical theory and applications of lock-in carrierographic image pixel brightness dependence on multi-crystalline Si solar cell efficiency and photovoltage

Abstract

A solar cell lock-in carrierographic image generation theory based on the concept of non-equilibrium radiation chemical potential was developed. An optoelectronic diode expression was derived linking the emitted radiative recombination photon flux (current density), the solar conversion efficiency, and the external load resistance via the closed-and/or open-circuit photovoltage. The expression was shown to be of a structure similar to the conventional electrical photovoltaic I-V equation, thereby allowing the carrierographic image to be used in a quantitative statistical pixel brightness distribution analysis with outcome being the non-contacting measurement of mean values of these important parameters averaged over the entire illuminated solar cell surface. This is the optoelectronic equivalent of the electrical (contacting) measurement method using an external resistor circuit and the outputs of the solar cell electrode grid, the latter acting as an averaging distribution network over the surface. The statistical theory was confirmed using multi-crystalline Si solar cells.

Lock-in and Heterodyne Carrierographic Imaging Characterization of Industrial Multicrystalline Silicon Solar Cells

“…5b. The solar efficiency is approximately proportional to the logarithm of the surface-integrated LICG amplitude, in agreement with theory [16].…”

“…Although for our case the depth distribution of the minority carrier in the base is not constant at 808 nm laser illumination, a similar logarithmic dependence of the surface-integrated CG signal on the photovoltage is observed. A detailed theoretical explanation of this fact has been developed in [16]. The statistical distribution peak shifts toward low radiative amplitudes with decreasing photovoltage under a smaller load resistance, Fig.…”

Contactless measurement of electrical parameters and estimation of current-voltage characteristics of Si solar cells using the illumination intensity dependence of lock-in carrierography (photoluminescence) images

“…Therefore, the quantum efficiency for radiative recombination of photogenerated carriers, g R (I i ), and the calibration factor for variable illumination intensity, C LIP (I i ), were estimated using Eqs. (15) and (16), respectively. The photocarrier radiative recombination flux J R (I i ), a function of illumination intensity, was calculated from Eq.…”

“…14 It has the advantage of filtering out the thermal infrared (non-radiative) component of the emission spectrum of de-exciting free photocarriers, and/or resolving the radiative vs. the non-radiative components through spectrally windowed modulation frequency scans, thereby being sensitive only to radiative recombination events when performing dynamic measurements of transport properties in semiconductors. 14 LIPI has been used 15,16 to determine solar cell efficiency and several electrical parameters (photogenerated current density, J g , saturation diode current density, J 0 , ideality factor, n, fill factor FF, and open-circuit voltage V OC ) under variable external load resistance at constant illumination intensity.…”

Series resistance imaging of silicon solar cells by lock‐in photoluminescence

“…It would cost longer inspection time and have relatively low signal to noise ratio especially when the emitted photoluminescence signal is poor. Lock‐in photoluminescence (LIPL) or lock‐in carrierography (LIC) , which combines the lock‐in principle and the PL method, can improve considerably signal to noise ratio (SNR) and realise a calibration‐free possibility.…”