• Energy Research

This article provides datasets containing three years worth of solar spectra for the optimum installation angle of 35° and the building-integrated-photovoltaics relevant vertical angle of 90°. These datasets were obtained by measuring the spectrally resolved solar spectra using a five minute interval, where two sets of spectrometers, which measure different ranges of the solar spectrum, were employed. In addition, a merged dataset of these two spectral measurements, related to every specific five minute interval measurement, is provided. An analysis and interpretation of the data using only year the 2020 is provided in "Measurement and analysis of annual solar spectra at different installation angles in central Europe" [1].

To achieve a monolithic series interconnection of tandem solar cell devices consisting of a perovskite top cell and a CIGSe bottom cell, a two-terminal interconnection scheme is introduced that includes an additional, fourth patterning step, the so-called iso-cut, which separates the window layer stack between the two solar cells. The implementation of this interconnection scheme requires a process development for a total of four structuring steps, which was achieved by systematically varying the laser parameters. Based on a detailed characterization of the individual scribe line properties with respect to their scribe line depth, morphology, electrical functionality, chemical composition and their influence on adjacent and underlying layers, the optimal patterning parameters and suitable process windows were derived for each step, which is a prerequisite for a loss-free monolithic series interconnection in a tandem module.

We investigate the performance of monolithic copper indium gallium selenide CIGS perovskite tandem solar cells with two different CIGS bottom device absorbers Cu In,Ga Se2 or Cu In,Ga S,Se 2 and with three different hole transporting layers HTLs NiOx SAM, NiOx Cu SAM and SAM alone. NiOx Cu is 2 wt copper doped nickel oxide and SAM is the MeO 2PACz [2 3,6 dimethoxy 9H carbazol 9 yl ethyl]phosphonic acid self assembled monolayer. The CIGSe is fabricated by physical vapor deposition PVD , has a Eg amp; 8764; 1.06eV, and a amp; 963;RMS,PVD amp; 8764; 65 nm, while the CIGSSe is fabricated by rapid thermal processing RTP , has a Eg amp; 8764; 1.01eV, and a amp; 963;RMS,RTP amp; 8764; 120 nm. While the current certified, 24.2 efficient, world record monolithic CIGSe perovskite tandem solar cell has previously been achieved with SAM as a stand alone HTL, this work investigates whether SAM can yield similarly high efficiencies also on industrially compatible, very rough RTP CIGSSe absorbers. We find that the devices with SAM as stand alone HTL suffer from severe FF and Voc losses and that NiOx Cu is needed to act as a shunt quenching layer below that SAM, ensuring conformal coverage of the rough bottom sub cell surface. Within this work the highest achieved in house measured PCEs for the RTP and PVD CIGS based tandems are 21.6 and 23.2 respectively, on a cell area of 1.08 cm2, both of which are obtained with NiOx Cu SAM as an HTL

The datasets provide three year-round worth of solar spectra for the optimum installation angle of 35° and the building-integrated-photovoltaics relevant vertical angle of 90°. The datasets were obtain measuring the spectrally resolved solar spectra in a five minute interval, using two sets of spectrometers which measure different ranges of the solar spectrum. In addition, the merge of these two spectra, related to every specific five minute interval measurement is provided. The data for each spectrometer and their merge are provided in compressed ZIP archives containing the CSV files related to a complete year of data for 2020, 2021 and 2022, respectively.

Abstract We present monolithic copper–indium–gallium–diselenide (Cu(In,Ga)Se2, CIGSe)-perovskite tandem solar cells with air- or N2-transferred NiO x :Cu with or without self-assembled monolayer (SAM) as a hole-transporting layer (HTL). A champion efficiency of 23.2%, open-circuit voltage (V o c ) of 1.69 V, and a fill factor (FF) of 78.3% are achieved for the tandem with N2-transferred NiO x :Cu + SAM. The samples with air-transferred NiO x :Cu + SAM have V o c and FF losses, while those without SAM are heavily shunted. We find via x-ray and UV photoelectron spectroscopy that the air exposure leads to non-negligible loss in the Ni2+ species and changes in the NiO x :Cu’s work function and valence band maxima, both of which can negatively impact the V o c and the FF of the tandems. Furthermore, by performing dark lock-in thermography, photoluminescence (PL), and scanning electron microscopy studies, we are able to detect various morphological defects in the tandems with poor performance, such as ohmic shunts originating from defects in the bottom CIGSe cell, or from cracking/delaminating of the perovskite top cell. Finally, by correlating the detected shunts in the tandems with PL-probed bottom device, we can conclude that not all defects in the bottom device induce ohmic shunts in the tandems since the NiO x :Cu + SAM HTL bi-layer can decouple the growth of the top device from the rough, defect-rich and defect-tolerant bottom device and enable high-performing devices.

Laser-based patterning for serial interconnection of chalcopyrite (i.e., Cu(In ${}_{\rm{x}},\text{Ga}_{\rm{1-x}}$ )Se2 or CIGSe) solar cells was obtained by 1) laser ablation using picosecond (ps) pulses, 2) local phase transformation using nanosecond (ns) laser pulses, and 3) conventional needle-based patterning. All three patterning approaches cause a modification of the material properties in the vicinity of the actual P2 scribing lines, which affects and limits the electrical functionality of the interconnection, and thus has to be considered for positioning the P3 scribe. Thus, the extension and the properties of the affected zone aside the P2 scribe was investigated through spectral and spatial photoluminescence (PL). From the depletion of the PL intensity when approaching the scribing line and a peak shift analysis it is concluded that the laser-affected zone is distinctively larger than visual inspections suggest. Even putatively ultrashort, nonthermal ps pulses cause material modifications which might be facilitating recombination losses and thus limiting solar cell efficiencies. For ps laser patterning the affected area is even larger than for the ns laser patterning, due to a modification of the band structure and to thermal decomposition. Evolving subpeaks at the low energy tails are found to originate from Cu-related flat defect levels, i.e., Cu vacancies ( $V_{{\rm{Cu}}}$ ) and antisites (Cu In), created upon laser impact. These findings provide insights into laser-based material modification and provide beneficial information for minimizing the dead area resulting from laser-based monolithic interconnection.

The solar spectra in outdoor installations is very seldom equal to that under standard test conditions. This points to the importance of measuring, analyzing and understanding the implications of solar spectra variations with respect to the performance of solar cells. In this work, we present and analyze one year of sun spectra measured at two different angles in central Europe, where the spectrometers were installed at the optimum inclination angle and in vertical orientation, the latter being relevant for building integrated photovoltaics. We report for the first time the differences between the two inclination angles in terms of key performance indicators, such as average photon energy, blue fraction and spectral factor. Moreover, we show the impact of these spectral changes on the maximum current density of ideal single junction and tandem devices in tilted and vertical orientations. Red shifted solar spectra were more often found at the vertical installation in comparison to the optimum installation angle, which translated into up to 30 lower current mismatch losses in idealized tandem devices throughout the year

Abstract This work presents the validation of a heuristic model, which predicts the electrical characteristics of CIGSSe thin film solar modules. This model is based on four-coefficient equations, used to determine electrical parameters from photovoltaic devices such as open circuit voltage, short circuit current, current at maximum power point and maximum power point. The coefficients are obtained numerically by fitting these equations to measured datasets related to various irradiances and module temperatures. These four coefficients or predictors per parameter can then be used to calculate a parameter at different conditions. The datasets employed in this work were obtained from thin film CIGSSe modules, measured under both controlled laboratory and operating outdoor conditions. The validation of the model is performed by comparing the presented approach to well-known established models and methods for module power rating including the international standards IEC and SAPM. The comparison is performed using statistical analysis, comparing the deviation between the predicted and the measured output power. Furthermore, the possibility of evaluating the temperature coefficients through this model is also explored. The proposed model has been applied and validated yielding high correlation coefficients for CIGSSe modules for energy rating, power output forecasting and temperature coefficient calculation.