The energy costs associated with separating tightly bound excitons (photoinduced electron-hole pairs) and extracting free charges from highly disordered low-mobility networks represent fundamental losses for many low-cost photovoltaic technologies. We report a low-cost, solution-processable solar cell, based on a highly crystalline perovskite absorber with intense visible to near-infrared absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight. This "meso-superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages of more than 1.1 volts, despite the relatively narrow absorber band gap of 1.55 electron volts. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite.

https://science.sciencemag.org/content/sci/early/2012/10/03/science.1228604.full.pdf

Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

Many different photovoltaic technologies are being developed for large-scale solar energy conversion. The wafer-based first-generation photovoltaic devices have been followed by thin-film solid semiconductor absorber layers sandwiched between two charge-selective contacts and nanostructured (or mesostructured) solar cells that rely on a distributed heterojunction to generate charge and to transport positive and negative charges in spatially separated phases. Although many materials have been used in nanostructured devices, the goal of attaining high-efficiency thin-film solar cells in such a way has yet to be achieved. Organometal halide perovskites have recently emerged as a promising material for high-efficiency nanostructured devices. Here we show that nanostructuring is not necessary to achieve high efficiencies with this material: a simple planar heterojunction solar cell incorporating vapour-deposited perovskite as the absorbing layer can have solar-to-electrical power conversion efficiencies of over 15 per cent (as measured under simulated full sunlight). This demonstrates that perovskite absorbers can function at the highest efficiencies in simplified device architectures, without the need for complex nanostructures.

Efficient planar heterojunction perovskite solar cells by vapour deposition

Within the space of a few years, hybrid organic–inorganic perovskite solar cells have emerged as one of the most exciting material platforms in the photovoltaic sector. This review describes the rapid progress that has been made in this area.

The emergence of perovskite solar cells

Organic electronics are beginning to make significant inroads into the commercial world, and if the field continues to progress at its current, rapid pace, electronics based on organic thin-film materials will soon become a mainstay of our technological existence. Already products based on active thin-film organic devices are in the market place, most notably the displays of several mobile electronic appliances. Yet the future holds even greater promise for this technology, with an entirely new generation of ultralow-cost, lightweight and even flexible electronic devices in the offing, which will perform functions traditionally accomplished using much more expensive components based on conventional semiconductor materials such as silicon.

The path to ubiquitous and low-cost organic electronic appliances on plastic

Iron concentration imaging has been proven to be a very valuable analysis technique for silicon material characterization. We applied this method to determine the influence of a low temperature annealing after surface passivation on the interstitial iron concentration. The influence of hydrogen passivation induced by silicon nitride passivation is estimated by comparison of silicon nitride and aluminum oxide passivation. The second part of this work deals with systematic errors inherent to the iron concentration technique. Simulations show under which conditions errors occur due to the non-uniformity of carrier profiles.

Quantitative Iron Concentration Imaging

In this work we characterised recombination active defects in standard multicrystalline silicon block material by investigating the effect of a wet thermal oxidation step at 800 degC with fast temperature ramps on the effective lifetimes measured by the CDI and QSSPC methods. The average lifetime was significantly decreased by the oxidation step. An increase in the concentration of interstitial iron as well as an increase in the concentration of trapping centres after the oxidation step was observed. A detailed investigation revealed an increase in the recombination activity of grain boundaries. Modeling of measured carrier density profiles indicates that iron dissolves from precipitates in grain boundaries and diffuses into the grains during the process. It was found that iron represents a major part of the active defect concentration in the investigated multicrystalline material after the applied oxidation process

Redistribution of Recombination Active Defects and Trapping Effects in Multicrystalline Silicon After Wet Thermal Oxidation

In expectation of high potentials for cost reduction, many new approaches for thin film solar cell concepts achieved increased attention in the last time With improving efficiencies, the accurate determination of the solar cell parameters has received growing attention Calibration laboratories, such as the calibration laboratory of Fraunhofer ISE (ISE CalLab PV Cells), need to develop procedures to determine reliable solar cell parameters of such technologies, in accordance with standard testing conditions (STC, IEC 60904-3) A central requirement is the control of the junction temperature Many thin film technologies, such as organic solar cells, need to be encapsulated in order to protect the material from environmental influences This means that the junction temperature cannot be determined by direct probing, and other methods are required If the solar cell is additionally affected by light soaking, the VOC-method also cannot be performed to determine the junction temperature Model calculations were performed to predict the spatial and temporal distributions of changes in the temperature of an encapsulated thin film layer These are confirmed by experiments with specially prepared organic solar cells that also contained a temperature sensor and by infrared recordings Further experiments to understand the nature of light soaking and investigate the use of the VOC-method were performed

Determining the junction temperature for stc measurements of thin film solar cells

What photons tell us about solar cells – imaging diagnostic techniques

We introduce a novel application of modulated free carrier absorption (MFCA) for measuring minority carrier lifetimes in multicrystalline silicon with high spatial resolution. The improved lateral resolution compared to other contactless techniques allows the correlation between these lifetime maps and solar cell characteristics as well as microscopic properties, like dislocations, precipitates, oxygen concentration, etc. Comparisons of the lifetime maps measured on the starting material and light beam induced current (LBIC) maps exhibit a very good qualitative correlation of the structures observed in both cases. In addition, correlations to microscopic characteristics like high dislocation density in regions with low lifetimes are investigated and a comparison with spatially resolved FT-IR measurements of the interstitial oxygen concentration is performed.

Wilhelm Warta

Papers

Quantitative Iron Concentration Imaging

Redistribution of Recombination Active Defects and Trapping Effects in Multicrystalline Silicon After Wet Thermal Oxidation

Determining the junction temperature for stc measurements of thin film solar cells

What photons tell us about solar cells – imaging diagnostic techniques

Comparison of spatially resolved carrier lifetimes in mc-Si with solar cell and material characteristics