Degradation from ultraviolet (UV) radiation has become prevalent in the front of solar cells due to the introduction of UV‐transmitting encapsulants in photovoltaic (PV) module construction. Here, we examine UV‐induced degradation (UVID) in various commercial, unencapsulated crystalline silicon cell technologies, including bifacial silicon heterojunction (HJ), interdigitated back contact (IBC), passivated emitter and rear contact (PERC), and passivated emitter rear totally diffused (PERT) solar cells. We performed UV exposure tests using UVA‐340 fluorescent lamps at 1.24 W·m⁻² (at 340 nm) and 45°C through 4.02 MJ·m⁻² (2000 h). Our results showed that modern cell architectures are more vulnerable to UVID, leading to a significant power decrease (−3.6% on average; −11.8% maximum) compared with the conventional aluminum back surface field (Al‐BSF) cells (<−1% on average). The power degradation is largely caused by the decrease in short‐circuit current and open‐circuit voltage. A greater power decrease is observed in bifacial cells with rear‐side exposure compared with those with front‐side exposure, indicating that the rear side is more susceptible to UV damage. Secondary ion mass spectroscopy (SIMS) confirmed an increase in hydrogen concentration near the Si/passivation interface in HJ and IBC cells after UV exposure; the excess of hydrogen could result in hydrogen‐induced degradation and subsequently cause higher recombination losses. Additionally, surface oxidation and hot‐carrier damage were identified in PERT cells. Using a spectral‐based analysis, we obtained an acceleration factor of 5× between unpackaged cells (containing a silicon nitride antireflective coating on the front) in the UV test and an encapsulated module (with the front glass and encapsulant blocking 90% of the UV at 294 nm and 353 nm, respectively) in outdoor conditions. From the analytical calculations, we show that a UV‐blocking encapsulant can reduce UV transmission in the module by an additional factor of ~50.

A silicon heterostructure photovoltaic system fielded for 10 years has been investigated in detail. The system has shown degradation, but at a rate similar to an average Si system, and still within the module warranty level. The power decline is dominated by a nonlinear V$_{\rm {oc}}$ loss rather than more typical changes in I$_{\rm {sc}}$ or Fill Factor. Modules have been evaluated using multiple techniques including: dark and light I–V measurement, Suns-V$_{\rm {oc}}$, thermal imaging, and quantitative electroluminescence. All techniques indicate that recombination and series resistance in the cells have increased along with a decrease of factor 2 in minority carrier lifetime. Performance changes are fairly uniform across the module, indicating changes occur primarily within the cells .

The long-term performance degradation of five different types of commercial crystalline silicon (c-Si) photovoltaic (PV) modules (one sample for each type) in the tropics, or more specifically the tropical rainforest climate “Af” by the Köppen climate classification (Singapore), is investigated over a period of seven years, based on outdoor I–V measurements at 10-s intervals. The degradation rates of these c-Si PV modules, based on the temperature-corrected performance ratio, range from –0.03 to –0.47%/year, which satisfy the products’ performance warranty. Further analysis of the short-circuit current (I $_\text{sc}$ ), open-circuit voltage, and fill factor for these modules shows that the performance degradation is mainly attributed to the I $_\text{sc}$ loss. The possible causes of the module performance deterioration are also discussed.

Accelerated potential-induced degradation (PID) testing of photovoltaic modules is conventionally conducted in the dark and at high temperature and humidity levels without considering the influence of illumination. This study investigates the impact of illumination on the polarization-type PID (PID-p) on two different types of encapsulated (glass/backsheet) crystalline silicon solar cells: 1) n-type bifacial passivated emitter rear totally diffused (the front side is facing glass and PID-stressed); and 2) p-type bifacial passivated emitter and rear cell (the rear side is facing glass and PID-stressed). The samples are stressed under the conditions of −1000 V, 40 °C, and 40% relative humidity and at different irradiance levels (xenon lamps). While the type-A modules show no reduction in PID-p sensitivity under illumination up to 800 W/m2, PID-p in the type-B modules is arrested by the light at an irradiance level as low as 10 W/m2. Furthermore, PID-degraded type-B modules (degradation induced in the dark) exhibit a rapid recovery (full recovery in 20 min) upon exposure to light (40 W/m2). External quantum efficiency measurements on the type-B modules show that ultraviolet from 300 to 400 nm is mainly responsible for the fast recovery.