• Energy Research

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.

In this contribution, the impact of thermal stress on Cu(In,Ga)Se $_{2}$ (CIGSe) thin film photovoltaic devices is investigated. The tolerance of such devices to high temperatures is of particular interest for processing transparent conductive oxides (TCOs) in order to further close the gap to the theoretical efficiency limit and for their potential use as bottom devices in tandem applications in order to overcome the theoretical efficiency limit of single junction solar cells. When CdS-buffered CIGSe high efficiency solar cells are subjected to thermal stress, elemental interdiffusion of Na and Cd between the absorber and the window layers as well as chemical reactions at the CIGSe/CdS interface result in a degraded power conversion efficiency (PCE). Here, we compare the degradation mechanisms of CdS and GaO $_{x}$ buffered CIGSe solar cells under thermal stress. A model explaining the observed degradation behaviors is proposed.

AbstractPolycrystalline Cu(In,Ga)Se2 (CIGSe) thin‐film solar cells exhibit gradual onset in their external quantum efficiency (EQE) spectra whose shape can be affected by various CIGSe material properties. Apart from influences on the charge‐carrier collection, a broadening of the EQE onset leads to enhanced radiative losses in open‐circuit voltage (Voc). In the present work, Gaussian broadening of parameters describing the EQE onset of thin‐film solar cells, represented by the standard deviation, 𝜎total, was evaluated to study the impacts of the effective band‐gap energy, the electron diffusion length, and the Ga/In gradient in the CIGSe absorber. It is shown that 𝜎total can be disentangled into contributions of these material properties, in addition to a residual component 𝜎residual. Effectively, 𝜎total depends only on a contribution related to the Ga/In gradient as well as on 𝜎residual. The present work highlights the connection of this compositional gradient, the microstructure in the polycrystalline CIGSe absorber, and the luminescence emission with the residual component 𝜎residual. It is demonstrated that a flat band‐gap with no compositional gradient in the bulk of the CIGSe absorber is essential to obtain the lowest 𝜎total values and thus result in lower recombination losses and gains in Voc.

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].