This PDF file contains the front matter associated with SPIE Proceedings Volume 12660, including the Title Page, Copyright information, Table of Contents and Conference Committee list.

The lifetime of organic solar cells critically depends on the photochemical stability of the materials. To shed light on the photostability of novel Y-series electron acceptors, we investigate the evolution of optical properties and composition during one-sun illumination in ambient atmosphere of thin films of the small-molecule acceptor Y5 and its copolymers PF5-Y5 and PYT. We employ UV-vis, Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS), to assess changes in these properties as a function of illumination time. UV-Vis spectra show that PF5-Y5 undergoes rapid photobleaching, while the Y5 spectrum remains essentially unaffected even after 30 hours of exposure. The absorption spectrum of PYT, which contains a different co-mer than PF5-Y5, is only weakly affected. XPS C1s spectra of the PF5- Y5 film show a decreasing main peak and the development of a new component after 30 hours exposure, while the Y5 film surface composition remained intact. The photodegradation products of PF5-Y5 are characterized by the presence of new carbonyl groups, emerging as absorption bands in the FTIR spectra, while such spectral changes are absent for the Y5 film, indicating that Y5 is resistant to photooxidation, while PF5-Y5 undergoes photochemical reactions. The faster photodegradation of PF5-Y5 compared to Y5 and PYT raises the question about the role of the copolymer’s BDT moiety in the photooxidation. These new insights on the dependence of the photostability of acceptor molecules on their molecular structure are expected to contribute to the design of stable acceptor copolymers for organic solar cells with long operational lifetimes.

In this study, we focus on the precise control of electronic and ink properties for hole transport materials (HTM) and photoactive materials, consisting of p-type polymers (donors) and non-fullerene acceptors (NFA), to develop solution processable near-infrared (NIR) and short-wave infrared (SWIR) organic photodiodes(OPDs) with consistent performance over different batches. We observed fluctuations in the turn-on voltage of NIR-OPD devices when using different batches of our HTM. Regression analysis revealed a strong correlation between the turn-on voltage and specific factors in the polymer. By implementing an improved purification scheme, we successfully suppressed these fluctuations. Moreover, we investigated the impact of p-type polymer structure and properties on device performance and solubility in non-halogenated solvents. A trade-off between molecular weight and EQE of NIR-OPDs was identified in a commercially purchased polymer. However, by optimizing the synthesis pathway, we achieved compatibility between these parameters in our polymer and extended the ink storage period to over three months without compromising EQE and dark current. Additionally, we introduce a novel NFA, IR6, which exhibits an impressive EQE of 45% at 1100 nm with a dark current of 4 × 10 ⁻⁵ mA/cm⁻² . These advancements in precise material control and novel NFA offer promising prospects for the commercialization of solution-processable NIR-OPDs, making them viable candidates for high-performance near-infrared sensing applications.

The photonic luminescent solar concentrator (LSC), a flat light-refocusing device, has been proposed as a solution to unlock low-cost, high efficiency solar modules because of its potential to achieve concentrations much higher than traditional lenses [1]. Further, because of the inherent wavelength selectivity of the structure, using multiple wavelength LSCs could finally enable spectrum-splitting designs wherein the broadband solar spectrum is demultiplexed onto multiple bandgap cells (multijunction cell), enabling efficiencies exceeding 50% [2]. Here, we explore how the unique surface sensitivity of perovskite nanocrystals can be exploited to significantly increase the light trapping in LSC designs. Inorganic lead halide perovskites (CsPbX₃(X=halide)) have exhibited remarkable optical properties that make them well suited for LSCs, such as high quantum yields [3]. Further, the transition dipole moment of perovskite nanocrystals (governs directional emission) is highly controllable based on local environment [4]. We show how using bilayers of perovskite nanoparticles can enhance directional emission of perovskites for use in LSCs. UV-vis spectroscopy quantifies spectral interaction of these layers and TEM imaging shows particle packing and alignment. Films are characterized via back focal plane (Fourier) imaging, which quantifies the angle-resolved light emission pattern. Preliminary results show that 270 nm thick films of CsPbBr3 cubes (emission = 515 nm) emit light randomly, while 270 nm thick films of CsPbB3 cubes on top of a layer of CsPbBr₃ nanoplates (emission = 450 nm) have a higher dipole angle (40°), favoring total internal reflection modes. This change in alignment results in a trapping improvement of 4% [5].

We report two types of the tin-based solar cells, namely, lead-free tin perovskite solar cells (Sn-PVK-PV), tin lead alloyed perovskite solar cells (SnPb-PVK-PV). Tin oxide is well-known as the electron transport layer of solar cells such as Pb-PVK PV, dye-sensitized solar cells and organic solar cells. We found that SnOx works as the HTL of the Sn-PVK PV. The basic structure is as follows: FTO glass/SnOx/Sn-PVK/C60/BCP/Ag. Efficiency over 14% and the carrier dynamics are reported. All-perovskite tandem solar cells consisting of Pb-PVK-PV (top cell) and PbSn-PVK-PV (bottom cells) are reported. PbSn-PVK PV efficiency was improved by using hybrid SAM layers working as the HTL. The efficiency over 26% is reported.

Perovskite solar cells are ideal candidates for tandem solar cell technologies thanks to their bandgap tunability and high efficiency, but their stability needs to be improved for commercial applications. The operational stability of encapsulated PSCs with wide bandgaps suitable for regular and bifacial tandems was tested with 1-sun illumination and at different temperatures. For all temperatures, the decay in performance is due to a drop in current at MPP conditions, and XRD shows perovskite decomposition. Interestingly, open-circuit-voltage-decay measurements reveal a higher ion concentration for the degraded device, which correlates with the drop in current.

We demonstrate efficient solar cells based on an active layer of methylammonium lead iodide (MAPbI3) co-deposited via vapor transport deposition (VTD). In VTD organic and metal-halide precursor vapors are transported by carrier gas to a cooled substrate where film formation occurs. Our system design enables control over a range of process parameters allowing co-deposition and composition tuning of the final perovskite film. The impact of VTD processing conditions on film composition and solar cell performance will be discussed, with emphasis on tuning the lead iodide content in MAPbI3 films to realize power conversion efficiencies >10%.

The study of unstable interfaces in perovskite semiconductors requires crucial information on interfacial composition, chemical gradients, and impurity distribution. A versatile technique called TOF-SIMS can provide this information effectively. Solar cells employing methylammonium lead triiodide as the photoactive layer were fabricated, utilizing PEDOT:PSS or NiOx thin film as the hole transporting layer, and PCBM plus ZnO as the electron transporting layer. These inorganic and organic layers were deposited through magnetron sputtering and solution processing, respectively. To comprehensively examine each interface within the device structure, a detailed TOF-SIMS study was conducted.

We have demonstrated theoretically and experimentally that the current induced by an interference pattern moving at constant velocity can be used to determine the ion mobility and activation energy in perovskite semiconductors. The frequency dependence of the signal has features predicted by theory: the high-frequency peak corresponds to the electron/hole photoconductivity relaxation process, and the low-frequency peak occurs when the velocity of the interference pattern synchronizes with the ion motion; by determining the peak’s position, it becomes possible to estimate the ion mobility. The values of ion mobility and activation energy agree with the data reported in the literature.

Solar energy has been relevant in recent years as a renewable source. On one side, halide perovskites have played an essential role as semiconductors with photovoltaic applications. This work studied the effect of reaction temperature on the synthesis of CsPbBr₃ perovskite quantum dots (PQDs) by the hot injection method. In this case, CsPbBr₃ PQDs are very stable compared to other halide perovskites. The XRD analysis indicated three crystalline phases were obtained: cubic of CsPbBr₃, orthorhombic, and rhombohedral of Cs₄PbBr₆. At a temperature of 130 °C, the cubic phase predominates at 57%. When the temperature increases to 155 and 180 °C, the cubic phase is obtained to a lesser extent, with 33% and 10%, respectively, and the orthorhombic and rhombohedral phases increase. SEM reveals that particle size increased from 8 to 36 nm due to the reaction temperature. The UV-vis results showed that the absorption spectra had a redshift of the visible spectrum from an absorption band from 487 to 514 and 522 nm. Likewise, the PL spectra demonstrate a peak of 501 to 517 and 515 nm as a function of temperature increase, where the calculated Full Width at Half Maximum (FWHM) indicates the purity of the color emitted. Tauc plots of the CsPbBr₃ PQDs showed band gap energies between 1.64 to 2.37 eV, which means these PQDs are interesting in photovoltaics. On the other hand, solar cells were fabricated using CsPbBr₃ PQDs, with the following architecture: FTO/c-TiO2/m-TiO2/PQDs/spiro-OMeTAD/Ag. The photovoltaic parameters were determined, obtaining with J_sc (4.10·10^-6 mA·cm^-2), Voc (0.434 V), FF (30.56%), and PCE (5·10^-4 %). In conclusion, the obtained PVs indicated the charge transport within the solar device in ambient conditions.

The lead-free halide-based perovskite is widely used because of its superior performance, long carrier diffusion length, narrow band emission, and tuneable bandgap. However, improvement of carrier lifetime and stability is the prime challenge for such perovskites. Therefore, reduced graphene oxide (rGO) is used as an additive material in CsSnI3 pristine perovskites to improve the optical, electronic, and structural properties. In this work, we synthesized the perovskite and rGO nanocomposite using the hot injection technique. We have performed photoluminescence (PL), ultraviolet spectroscopy (UV-Vis), X-ray diffraction (XRD), and Transmission electron microscopy (TEM) to understand the effect of rGO in Perovskite. In PL, a peak is found at ~ 782 nm for as-synthesis perovskite and after the 1% rGO incorporation, the peak is shifted towards the higher wavelength around ~ 811 nm. In XRD, the multiple diffraction peaks for the CsSnI3 perovskite and rGO nanocomposite are observed at 27.46°, 39.41°, 48.48°, 56.93°, and 64.38°, which originated from the indexing planes of (221), (112), (540), (082), and (053), respectively. The dominant peak (221) shifts towards the higher angle (0.07°) after 5% rGO incorporation. The UV-Vis spectroscopy confirms bandgap reduction after rGO incorporation in pristine CsSnI3 perovskite. The bandgaps of 1.64 eV and 1.56 eV are calculated from Tauc’s plot for CsSnI3 and rGO/CsSnI3 nanocomposite, respectively. Therefore, the rGO incorporation in the pristine CsSnI3 perovskite demonstrates highly promising properties, which opens the gateway towards the improvement of optoelectronics device performance.

Based on a drift-diffusion simulator, 2D modeling of perovskite/Si tandem solar cell with tunnel junction is presented in this work. Current matching is explored between the two sub-cells. It is demonstrated that the basic tandem cell can achieve conversion efficiency as high as 28.27% with open-circuit voltage and short-circuit current density as 2.04 V and 16.18 mA/cm2 , respectively. As approaches for cell design optimization, the results are also analyzed versus the thickness and the minority carrier recombination lifetime of the perovskite layer. Efforts to incorporate coating, to consider texture effect for the bottom Si cell as well as to look for alternative electron transport layer for the top junction are also performed, presented and discussed. Efficiency as high as 36.40% is further projected.