This PDF file contains the front matter associated with SPIE Proceedings Volume 12881, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

III-V devices are used in countless applications due to their excellent physical properties. They could become more prevalent, especially in area-intensive applications such as solar power, if they can achieve significant cost decreases through increasing scale. The development of high-throughput growth systems can help to achieve this scale, leading to the use of III-V devices in areas where they are not currently economically feasible. Here, we describe a pilot-production, pseudo inline HVPE reactor with the potential to greatly increase the throughput of III-V devices. We show computational modeling results that both informed system design and the understanding of the impact of different process parameters on the deposition. We show the throughput possibilities of this reactor with an example solar cell device design but note that this system is agnostic to the device structure and can be used to increase the throughput of lasers, LEDs, transistors, and more III-V devices.

III-V compound semiconductors provide a high degree of flexibility in bandgap engineering and can be realized through epitaxial growth in high quality. This enables versatile spectral matching of photovoltaic absorber materials as well as the fabrication of complex layer structures of vertically stacked subcells and tunnel junctions. This work presents progress in two fields of applications of III-V photovoltaics: concentrator solar cells and photonic power converters. We present latest results in advancing solar energy conversion efficiencies to 47.6% based on a wafer-bonded four-junction concentrator solar cell. Furthermore, we provide an overview of the latest development results regarding photonic power converters, showcasing several record devices. We briefly introduce a new metallization technique using electro-plated silver for handling high currents and first 10-junction InGaAs devices for optical telecommunication wavelengths. Overall, this paper highlights the potential of III-V compound semiconductors in achieving high efficiencies and spectral matching, offering promising prospects for future applications.

In this paper, we present a detailed analysis of capacitance-based defect characterization techniques on antimony selenide solar cells. Based on capacitance deep level transient spectroscopy (C-DLTS) measurements, we detect two majority carrier traps; however, the common rate window analysis method is not able to provide physically valid values of the activation energy and apparent capture cross-section. In order to understand this effect, we carried out an extensive analysis based on the exponential fit method. We provide experimental evidence that (i) the Arrhenius plot extracted by the rate window analysis is not reliable, since the variation in capacitance transient amplitude is not caused by the variation in time constant of the exponential transient. This is because (ii) the amplitude of the capacitance transient is related to the amount of trapped charge, which changes significantly with temperature due to a temperature-assisted injection process, as confirmed by capacitance transient measurements carried out in the filling phase. Moreover, analysis of the transients with different filling time shows (iii) an additional contribution by minority carriers injected by the n-side of the junction. All the results are (iv) confirmed by analysis at various filling voltage.

Quantum dot intermediate band solar cells involve nanoscale and microscale physical mechanisms that ultimately decide the operation of the cell in the intermediate band or single gap regime and must be considered for a proper description of the device behavior. In this work we discuss material- and device-level guidelines aimed at demonstrating truly intermediate band operation of quantum dot solar cells with the aid of numerical simulations built upon a hybrid modeling approach. Semiclassical transport is coupled with charge carrier transfer mechanisms involving localized states, allowing to merge the nanoscale and microscale pictures at a computational cost compatible with the simulation of a real solar cell structure.

In this paper we introduce the PVRD-FASP solver for studying carrier and defect transport in CdTe solar cells on an equal footing by solving 1D and 2D drift-diffusion-reaction model equations. The diffusion constants and activation energies of the defect and the defect chemical reactions require reaction rate constants that are calculated using density functional theory (DFT). The PVRD-FASP solver can propose solutions that can reduce the development cost of thin-film photovoltaics (TFPV) because up- and down-stream process optimization, required due to complex interactions, is replaced by predictive modeling. An in-house implementation of a machine-learning approach for modeling of Cu diffusion in the CdTe absorber layer of the CdTe solar cell is also discussed.

In this work, PSC with three different HTL dopants have been analyzed. By means of current-voltage characterization under light and dark conditions, EQE characterization in continuous, and transmittance spectral characterization we demonstrate that: (i) PSCs show an EQE peak efficiency in excess of 80% with a sharp edge at 550 nm, (ii) they show hysteresis in their electrical behavior, possibly due to ionic conduction; (iii) they show a good stability to reverse voltages down to -2.25 V. Being transparent at wavelengths above 550nm makes them suitable for agrivoltaic applications.

Optical wireless optical power transmission (OWPT) is a promising technology for a variety of data communication and sensing applications. It has superb properties compared to conventional wired power transmission methods, such as faster communication rate, longer detection range, better heat management capability especially for compact systems, better durability in various operating conditions, enhanced safety, lighter weight of the module, and improved overall robustness of these devices. A typical OWPT module consists of a light emitting source, such as light-emitting diodes (LEDs), vertical-cavity surface-emitting lasers (VCSELs), or edge-emitting lasers (EELs) which convert the input electrical power at the source into optical power. The output optical power from the light source is transmitted through an intermediary medium (such as air, optical fiber, waveguide) to a detector at the receiving-end of the module. The detector is usually based on an array of series-connected photovoltaic (PV) cells, in which it converts the absorbed optical power back into the electrical power as the system output. In this paper, we will demonstrate the smallest-to-date micro-PV array that can be used as the detector in the OWPT modules. Each array consists of multijunction PV cells with active areas between 30-150μm and are fabricated on semi-insulating GaAs substrate and series-connected to each other to form an array in order to efficiently absorb a monochromatic light at the wavelength of ~850nm. The PV array can be used to convert the incoming optical power into electrical power with the desired output voltage and current levels. High-temperature operating lifetime tests demonstrate the reliability performance of these devices with different aperture sizes at elevated operating temperatures. Also, formation of photo-carriers in the substrate has been shown to form a leakage current path underneath the PV array, in which it could significantly impact the performance of these devices. These results demonstrate the feasibility of fabricating micro-PV arrays for use in optical wireless power transmission systems that can have a wide variety of applications in low-power sensing and energy storage application.

CIGS solar cells are promising light-receiving elements for optical wireless power transmission (OWPT) systems because they are inexpensive and receive light in the long wavelength range that is relatively safe for human eyes. A photoelectric conversion efficiency η_pv of the CIGS solar cell (10 mm x 10 mm) on a metal substrate was examined under a 1064 nm laser irradiation. We obtained η_pv values of 31.2% and 26.8% under a 1064 nm laser irradiation of 0.9 W/cm² (84 mW) and 2.6 W/cm² (244 mW), respectively. In anticipation of social implementation, we also demonstrated the influence of the size of the laser irradiation area on the conversion efficiency of CIGS solar cells. The photoelectric conversion efficiency did not change when the irradiated area was varied. These results could expand the possibility of applying CIGS solar cells to OWPT systems.

Since optical wireless power transmission (OWPT) transmits light and generates power at remote targets, determining the position and attitude of the photovoltaic device (PV) from the transmitter is essential before power transmission. PV is robustly detected in various background illuminations utilizing the proposed differential absorption imaging, utilizing the intrinsic nature of PV as a semiconductor. In this method, images are captured using the absorbable and non-absorbable wavelengths of PV, and it is detected from the differential image of these wavelengths. Position estimation was investigated using stereo imagery with a set of conditions implying consistency between images captured by two independent sensors on the left and right. There is a minimum exposure time of the image sensor to ensure that these consistency conditions converge to certain values. It is strongly correlated with the positioning accuracy of the targets and also depends on the attitude angle of the target. Using these features of the minimum exposure time, the position and attitude of the targets were determined even in the case of an incomplete target image. There are diffuse and non-diffuse (specular) options for the reflection of the rear surface of the PV, and positioning accuracy is affected by these reflection characteristics. Experiments were conducted on a 33 × 23-inch optical bench. In the case of a specular target, although positioning accuracy was affected by attitude, its position was estimated within about a 2-inch error in a 20-degree full angular range, while its attitude was estimated within about a 10-15 degree error in a 60-degree full angular range.