Voltage dependent photocurrent collection in CdTe/CdS solar cells

Abstract

The voltage dependence of the photocurrent JL(V) of CdTe/CdS solar cells has been characterized by separating the forward current from the photocurrent at several illumination intensities. JL(V) reduces the fill factor (FF) of typical cells by 10–15 points, the open circuit voltage (VOC) by 20–50 mV, and the efficiency by 2–4 points. Eliminating the effect of JL(V) establishes superposition between light and dark J(V) curves for some cells. Two models for voltage dependent collection give reasonable fits to the data: (1) a single carrier Hecht model developed for drift collection in p‐i‐n solar cells in which fitting yields a parameter consistent with lifetimes of 10−9 s as measured by others; or (2) the standard depletion region and bulk diffusion length model fits almost as well. The simple Hecht‐like drift collection model for photocurrent gives very good agreement to J(V) curves measured under AM1·5 light on CdTe/CdS solar cells with FF from 53% to 70%, CdTe thickness from 1·8 to 7·0 µm, in initial and stressed states. Accelerated thermal and bias stressing increases JL(V) losses as does insufficient Cu. This method provides a new metric for tracking device performance, characterizes transport in the high field depletion region, and quantifies a significant FF loss in CdTe solar cells. Copyright © 2007 John Wiley & Sons, Ltd.

Spectral Responses in Quantum Efficiency of Emerging Kesterite Thin-Film Solar Cells

“…However, it is argued that including the non-uniform electric field with additional parameter sets only adds confusion with no additional insights [29]. Hence, we will explore the quantum efficiency response with a constant electric field model for our analysis for simplification.…”

“…The absorption coefficient, α(λ) was taken from Ref. [28] and the front surface recombination velocity (S f ), the default depletion width is 0.3 µm, and the electron lifetime (τ n )w e re1 0 3 cm/s and 10 À9 s [29,30]. In Figure 3, the Q-E shape changes disproportionally with significant red light response reduction >600 nm as the uncompensated impurity concentration changes , and 10 À11 s.…”

Optimum Monochromatic Wavelengths for Solar Panel Testing and Conversion of Parameters to STC

“…The experiments were conducted on monocrystalline, multicrystalline and thin film solar panels by using natural sunlight and simulated lights. Even though researches in this area started decades ago, till date the researches combining solar simulator and solar panel are very few [1][2][3][4][5][6][7][8][9][10][11][12][13]. Researchers Shogo Kohraku and Kosuke Kurokawa for the first time used LED lights to measure the spectral response characteristics of solar cells [14].…”

Effect of hysteresis on measurements of thin-film cell performance

“…5 was obtained simply by setting J p =0 in the dark J-V simulation. In general, polycrystalline thin film solar cells do not demonstrate this degree of superposition [12]. However, as discussed in reference [11], the differences between actual J-V data and the PSpice simulations can be used to determine this voltage-dependent photocurrent loss.…”