Passivated, carrier-selective contacts have enabled a recent surge in the efficiency of crystalline silicon solar cells by reducing the Shockley-Read-Hall recombination at the electrical contacts for the cell. They operate by allowing the extraction of only the majority carriers from the absorber, i.e., the c-Si wafer. The molybdenum oxide and nickel stack is known to form an effective hole-selective contact. However, the parasitic optical losses they introduced limit the quantum efficiency and therefore efficiency of solar cells featuring these materials. In this work, we introduce photonic nanostructures with reduced parasitic losses in the contacts and enhancement of light trapping in the active area of the cell. The optimized structure shows its potential for increasing photogenerated current density and efficiency as a result.
PV module reliability is alsways an important issue for PV industry. In an outdoor PV system, PV modules suffer from degradation due to different factors. It is then very important to determine the loss mechanisms of a PV module and making improvement based on this. It is found in this work that due to mismatch effect, using fitting method to extract <i>I-V</i> characteristics might not be well applied on a PV module, especially when it has non-uniform degradation problem. This work proposes a method to accurately quantify the power loss of PV modules due to different degradation mechanisms, including series resistance (R<sub>s</sub>) loss, non-uniform shunting loss and number of shunted cells, uniform shunting loss, uniform current loss, non-uniform current (mismatch) loss, recombination current (J<sub>01</sub> and J<sub>02</sub>) losses of a PV module. All required input information are the measured current-voltage (<i>I-V</i>) curves and short circuit current- open circuit voltage (<i>I<sub>sc</sub>-V<sub>oc</sub></i>) of PV module initial state and final state. The method is first applied to a simulated PV module with various degradation problems. Power loss due to each loss mechanism for the simulated PV module is then extracted using the proposed method and a pie chart can be generated. Comparing with the actual power loss on each loss mechanism, the method proposed in this work is proved to be very accurate. The method is then further applied to a degradated PV module istalled in an outdoor PV system. The power loss on series resistance, shunting and current mismatch are effectively identified and the number of shunted cells is accurately calculated. In the real application, this method can be used in both indoor and outdoor characterization, which can be very beneficial for PV degradation analysis of PV modules and systems.
In this work, the use of manufacturing metrology across the supply chain to improve crystalline silicon (c-Si) photovoltaic (PV) module reliability and durability is addressed. Additionally, an overview and summary of a recent extensive literature survey of relevant measurement techniques aimed at reducing or eliminating the probability of field failures is presented. An assessment of potential gaps is also given, wherein the PV community could benefit from new research and demonstration efforts. This review is divided into three primary areas representing different parts of the c-Si PV supply chain: (1) feedstock production, crystallization and wafering; (2) cell manufacturing; and (3) module manufacturing.
Both the economic viability and energy payback time of photovoltaic (PV) systems are inextricably tied to
both the electrical performance and degradation rate of PV modules. Different module technologies exhibit
different properties in response to varying environmental conditions over time. The purpose of this study is
to quantify the effects of those differences on the life-cycle economical cost and energy payback time of
two fielded PV systems; one system comprised of polycrystalline silicon (c-Si) modules and one featuring
hydrogenated amorphous silicon (a-Si) modules. The DC operating current, DC operating voltage, AC
power, and conversion efficiency of each system have been monitored for a period of over four years, along
with plane-of-array (POA) irradiance, module temperature, and ambient temperature. Electrical
performance is evaluated in terms of final PV system yield (Y<sub>f</sub>), reference yield (Y<sub>r</sub>), and performance ratio
(PR), which are derived from the primary international standard used to evaluate PV system performance,
IEC 61724<sup>1</sup>. Degradation rates were evaluated over the four year period using regression analysis. The
empirically determined trends in long-term performance were then used to approximate the energy
produced by both system types under the same environmental conditions; most importantly, the same levels
of solar irradiation. Based on this modeled energy production and economic conditions specific to the state
of Florida, comparisons have been carried out for life-cycle costs and energy payback time.