Applications of Photovoltaic Technologies

Solar Cell-structure A solar cell is a P-N junction device Light shining on the solar cell produces both a current and a voltage to generate electric power. Busbar Antireflection coating Fingers Emitter Antireflection texturing (grid pattern) Base Rear contact

I-V Tester

Irradiance inhomogeneity Illumination Sources Class Spectral Match Irradiance inhomogeneity Temporal Instability   Long Term Short Term A 0.75 - 1.25% 2% 0.5% B 0.6 - 1.4% 5% C 0.4-2.0% 10% Table: Solar simulator classification according to IEC 60904-9 Ed. 2.0.

No Resistive Losses Solar Cell model The I-V relation is given as: I V ID V IL Io －dark saturation current , IL －light generated current. , n －ideality factor .

Solar Cell I-V Curve V I I (diffu.) I0 A P-N junction in the dark consumes power, as it can be operated in 1st or 3rd quadrant Under illumination solar cell can be operated in the fourth quadrant corresponding to delivering power to the external circuit Effect of solar radiation on the I-V curve Current in the illuminated solar cell is negative, flows against the conventional direction of a forward diode

Solar Cell I-V Curve Solar cell parameters I Isc Pm Im V Voc - open circuit voltage, Isc - short circuit current, Pm - maximum power point Im, Vm – current and voltage at maximum power point FF – fill factor η – efficiency Rs – series resistance Rsh – shunt resistance Isc I Vm Im Voc Pm V Usual I-V plot of solar cell – Current is shown on positive y -axis

Short-Circuit Current, Isc Vm Im Voc Pm X The short-circuit current is the current through the solar cell when the voltage across the solar cell is zero (i.e., when the solar cell is short circuited). The short-circuit current is due to the generation and collection of light-generated carriers. The short-circuit current is the largest current which may be drawn from the solar cell. At V=0  I = -IL= Isc

Open Circuit Voltage: Voc Isc I Vm Im Pm X Voc The open-circuit voltage, Voc, is the maximum voltage available from a solar cell, and this occurs at zero current. The open-circuit voltage corresponds to the amount of forward bias on the solar cell junction due to illumination. At I=0  V = Voc

Maximum power: Pm I Isc Pm Im Pm = Im x Vm Power out of a solar cell increases with voltage, reaches a maximum (Pm) and then decreases again. Im Power Vm Voc Pm = Im x Vm Remember we get DC power from a solar cell

Fill Factor: FF I Im Ideal diode curve Isc The FF is defined as the ratio of the maximum power from the actual solar cell to the maximum power from a ideal solar cell Pm Im Vm Voc Graphically, the FF is a measure of the "squareness" of the solar cell

Efficiency: η I Isc Pm Im Vm Im Pm X Voc Power Efficiency is defined as the ratio of energy output from the solar cell to input energy from the sun. The efficiency is the most commonly used parameter to compare the performance of one solar cell to another. Efficiency of a cell also depends on the solar spectrum, intensity of sunlight and the temperature of the solar cell.

Four Point Probe Resistivity Measurements

Characteristic resistance, Rch Effect of Rs and FF Isc Voc V I Characteristic resistance, Rch Medium Rs Large Rs Normalized series resistance, rs Slope of the I-V curve near Voc gives indication about Rs Effect of series resistance on the FF and maximum power

Effect of Rsh on FF Isc Normalized shunt resistance, rsh Medium Rsh I Voc V I Normalized shunt resistance, rsh Medium Rsh Slope of the I-V curve near Isc gives indication about Rsh Effect of series resistance on the FF and maximum power

ScienceTech 150W太陽光模擬器 機型：ScienceTech 150W太陽光模擬器與IV 量測系統 Substrate：> 5.0 cm x 5.0 cm 可量測範圍：0.1V to 1.0V I-V曲線中之各項性能參數：開路電壓（Voc）、短路電 流（Isc）、最大輸出功率（Pmp）、並自動計算填充因子(fill factor) 、太陽電池效率(efficiency) 具有溫控功25℃

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IV measurement

IV Analysis

全波段入射光子轉換效率光度計(IPCE)

Quantum Efficiency Quantum efficiency (Q.E.) is the ratio of the number of carriers collected by the solar cell to the number of photons of a given energy incident on the solar cell. Internal quantum efficiency (IQE) refers to the efficiency with which photons that are not reflected or transmitted out of the cell can generate collectable carriers. External quantum efficiency (EQE) of a silicon solar cell includes the effect of optical losses such as transmission and reflection.

Quantum Efficiency