Validation of spectral response polychromatic method measurement of full size photovoltaic modules using outdoor measured data

This paper presents the validation of a polychromatic method of spectral response measurement applied to full size mono-crystalline silicon photovoltaic modules using outdoor measured data. The difference between short-circuit current modelled from the measured spectral response and outdoor spectral irradiance and the directly-measured current is below 5% which confirms the validity of the spectral response curve obtained using the polychromatic measurement method

Spectral changes of solar simulator xenon flash bulbs over lifetime and its effects on measurement uncertainty

The effects of lamp age on the spectral output of solar simulator xenon flash lamps and spectral output measurement uncertainty on the spectral mismatch are investigated. It is demonstrated that the spectrum of an older lamp set has a relatively lower blue and larger red content compared to a new set of bulbs. Measurements over the life-time of several sets of bulbs showed large unexpected variations due measurement uncertainty in spectral measurements themselves. The main influencing factors are investigated and a faulty temperature control is found to be the main source of uncertainty. It is shown that this alone can affect the mismatch calculation to a larger degree than the MMF would correct in itself

Spectral response measurements of photovoltaic devices using a pulsed source solar simulator

This paper presents a method for spectral response determination of photovoltaic devices using a commercially available pulsed source solar simulator and broadband filters. A fitting algorithm which is an iterative process is developed to model the spectral response curve. The method is tested on two different technologies of photovoltaic modules and the result shows that a fair agreement between the modelled and calibrated spectral response could be achieved with the improvement in the quality of measurement

Spectral response measurements of Perovskite solar cells

A new spectral response measurement routine is proposed that is universally applicable for all perovskite devices. It is aimed at improving measurement accuracy and repeatability of spectral response curves and current-voltage curve spectral mismatch factor corrections. Frequency response, effects of preconditioning as well as dependency on incident light intensity and voltage load on spectral response measurements are characterized on two differently structured perovskite device types. It is shown that device preconditioning affects the spectral response shape, causing errors in spectral mismatch factor corrections of up to 0.8% when using a reference cell with a good spectral match and a class A solar simulator. Wavelength dependent response to incident light intensity and voltage load is observed on both device types, which highlights the need to measure at short circuit current and maximum power point to correct spectral mismatch. The method with recommendations given ensures the correct measurement conditions are applied and measurements are corrected for instability in performance

I-V performance characterisation of perovskite solar cells

Interlaboratory comparisons of I-V performance measurements of perovskite solar cells have highlighted a clear need for development in application of measurement routines to deliver repeatable and comparable results. This work investigates the impact of applied measurement methodologies and conditions on I-V performance. Dependencies on light soaking, temperature effects and I-V curve trace speed are investigated. Furthermore, the problems faced with tracking the maximum power point are detailed. Measurement results on slow responding perovskite solar cells highlight the problems when tracing the I-V curve and show that maximum power point trackers can easily fail to track the real maximum output. Best practice advice is given with the aim to achieve realistic and reproducible characterisation results that are comparable among laboratories

The impact of spectral variation on the thermodynamic limits to photovoltiac energy conversion

Research into the fundamental limitations to photovoltaic power conversion has historically used a single predetermined set of conditions to define device performance limitations. This fails to account for the many variables involved in real-world situations. Previous work describing thermodynamic losses in solar energy conversion has typically used an analytical approach, precluding the use of real-world spectra. This paper describes a model which marries the advantages of the analytical approach with a numerical detailed balance calculation, enabling analysis of maximum attainable power conversion efficiency and associated loss mechanisms in photovoltaics under more representative conditions.Input spectra in the model are treated as separate beam and diffuse components, both in terms of power and subtended angle. Differences in conversion show that diffuse light is effectively under maximum concentration. This does not result in an efficiency gain since the equivalent energy is instead accounted for in the Carnot loss. The Carnot limit for the diffuse portion of the spectrum is therefore lower than that for direct light. Simulated hourly “clear sky” spectra across a year were analysed for five geographically disparate locations. Results showed that at higher latitudes narrower band gap devices have a similar maximum efficiency to those with wider band gaps, whilst at lower latitudes wider band gap devices have a slightly higher maximum efficiency. This is compounded by increased irradiance at lower latitudes. Irrespective of band gap, annual energy conversion shows little variation at lower latitudes, with greater conversion in summer being offset by reductions in winter at higher latitudes.</div

2.3% efficiency gains for silicon solar modules using a durable broadband anti-reflection coating

The front surface reflection losses from solar cover glass account for over 4% of incident light, limiting module efficiency. The application of a multilayer broadband antireflection coating reduces reflection losses over the wavelength range utilised by silicon solar cells. A 6-layer anti-reflection coating comprising SiO2 and ZrO2 has been deposited on glass using high rate pulsed-DC magnetron sputtering. The reflection losses are reduced by 2.4% absolute compared to uncoated glass. The increased light reaching the solar cell leads to improvements in Isc and spectral response, increasing the efficiency from 17.1 to 17.5%, a relative increase of 2.34%. The coating is environmentally robust. The sputtering process is already used for other high throughput applications by major glass manufacturers.</div

Measurement of flash solar simulator output spectra over bulb lifetime and the effects on spectral mismatch

The effects of solar simulator xenon flash lamp ageing and spectral output measurement uncertainty on the spectral mismatch are investigated. Initial measurements demonstrated that the spectrum of an older lamp set has a relatively lower blue and larger red content compared to a new set of bulbs. Measurements over the life-time of several sets of bulbs however, showed large unexpected variations due to measurement uncertainty in the spectral measurements themselves. The main influencing factors are investigated and a faulty temperature control is found to be the main source of uncertainty. It is shown that this alone can affect the mismatch calculation to a larger degree than the MMF would correct in itself

Damp‐heat induced degradation in photovoltaic modules manufactured with passivated emitter and rear contact solar cells

Corrosion is one of the main PV module failure mechanisms, as it can cause severe electrical performance degradation in PV modules exposed to hot and humid environments. Moisture penetrating a photovoltaic (PV) module may react with the metallic components causing corrosion. In addition, acetic acid which is produced by hydrolysis of ethylene vinyl acetate (EVA), the most common encapsulant, may further degrade metallic components. Corrosion is one of the main PV module failure mechanisms, as it can cause severe electrical performance degradation in PV modules exposed to hot and humid environments. The specific chemical reactions involved in the corrosion mechanisms for the different components are well understood. However, which of these causes the most serious degradation in the field, and therefore, most severe power loss is unknown. Moreover, the severity of corrosion in the absence of acetic acid is not yet well researched. This work distinguished between the front and rear side corrosion mechanisms and identified the different electrical signatures observed due to them. The experiment included damp-heat (DH) conditioning of single-cell mini-modules, containing passivated emitter and rear contact (PERC) solar cells, laminated with a polyethylene terephthalate (PET) based backsheet. Furthermore, half-encapsulated PERC PV cells were tested, with either the front or the rear side exposed. Electrical and material characterisation were conducted for the investigation of the sample degradation, and the performance decrease, related to the degradation of the rear surface passivation, was examined.</p

UK-India PV module measurement intercomparison [Abstract]

UK-India PV module measurement intercomparison [Abstract