Zhaoning Song

Perovskite solar cells (PSCs) hold strong potential for efficient and cost-effective photovoltaic technology, yet their device performance and stability remain hindered by interfacial limitations. In particular, the hole transport material (HTM) that contacts both the perovskite and the front contact can often be a bottleneck for device efficiency and durability. To overcome these challenges, we design and synthesize a series of carbazole- and fluorene-based polymers via palladium-catalyzed Buchwald–Hartwig amination, incorporating tunable N,N-dimethyl aminopropyl (N) and butanoate (COOCH3) side chains. We systematically investigate how these polar side chains affect the electronic properties of the buried perovskite interface and the overall device performance. Our results show that both N and COOCH3-functionalized HTMs significantly enhance interfacial compatibility with wide-bandgap perovskites, facilitating superior perovskite film formation and more efficient charge extraction. This enhancement yields wide-bandgap PSCs with a champion power conversion efficiency (PCE) of ∼17%, comparable to devices using commercial poly-triarylamine (PTAA) HTMs. These findings highlight that targeted side-chain engineering offers a simple and effective strategy to optimize polymer HTMs for wide-bandgap PSCs, providing valuable insights for the future design of perovskite optoelectronic devices.

Power generation in space is currently dominated by expensive III–V multi-junction photovoltaic (PV) devices and cheap crystalline silicon (c-Si) PV devices. Both of these technologies degrade rapidly in proton-radiation-rich space environments, such as the Van Allen belt. The present study of cadmium selenide telluride- (CdSeTe-) based PV devices exposed to 150-to-1500 keV proton irradiation with fluences up to 9 × 10 ¹³ cm ⁻² reveal a more radiation-hard alternative to III–V and c-Si PV technologies. We report on measurement and analysis of current density vs voltage (JV), external quantum efficiency (EQE), external radiative efficiency, and capacitance vs voltage (CV) characteristics. JV characteristics of As-doped CdSeTe devices show 80% remaining power conversion efficiency (PCE) relative to unexposed controls when exposed to 650 keV protons at a fluence of 10 ¹² cm ⁻² . Under these same irradiation conditions, Cu-doped CdSeTe devices demonstrate an even better 95% PCE retention compared with unirradiated control devices. Evidence of radiation-induced absorber p-type doping compensation is observed in the glass-side EQE at 0 V and CV characteristics of most of the irradiated CdSeTe:As devices, but clear compensation is evident only for the most heavily irradiated CdSeTe:Cu devices. Elevated blue-green photocurrent in the film-side 0 V EQE suggests a buried junction in the most heavily irradiated CdSeTe:As devices. Although CdSeTe:Cu devices are the more resilient of the CdSeTe structures, both CdSeTe-based technologies are radiation-hard when compared to c-Si and III–V multi-junction PV.

This study presents a comparative analysis of the open circuit voltage behavior of perovskite vs gallium arsenide (GaAs) solar cells at low temperatures relevant to space applications. While GaAs solar cells demonstrate high power conversion efficiencies and superior environmental stability, their widespread adoption is limited by high manufacturing costs. In contrast, perovskite solar cells have emerged as a promising alternative due to their high efficiency, excellent optoelectronic properties, and low fabrication costs. To evaluate and compare their optoelectronic characteristics and voltage losses at low temperatures, we have characterized both devices using temperature-dependent current–voltage (J–V) and photoluminescence-based radiative efficiency measurements in the range of 300–160 K. GaAs devices exhibited a linear increase in open-circuit voltage (Voc) with decreasing temperature, consistent with theory. In contrast, perovskite devices showed suppressed Voc enhancements and an S-shaped J–V response below 240 K. Using temperature-dependent external radiative efficiency measurements, we show that temperature-dependent entropic losses related to nonradiative recombination are higher in perovskite devices compared to GaAs at high temperatures, but the gap between the two shrinks substantially at lower temperatures. These findings provide valuable insight into temperature-dependent Voc in perovskite solar cells, particularly relevant for space deployment applications.

In order to power spacecraft in low earth orbit (LEO), the assessment of performance and stability over a wider temperature range than that encountered terrestrially is required. To this end, state-of-the-art all-perovskite tandem solar cells, attractive for their high power to mass ratio and radiation tolerance, were subjected to temperature extremes from –100 to +100 °C while utilizing maximum power point tracking (MPPT) to assess the in-operando performance under simultaneous thermal cycling and AM0 illumination. These findings show that the wide band gap (WBG) subcell tuned to maximize power output with AM0 illumination undergoes severe phase segregation at temperatures above 50 °C, with only partial recovery within the 45-min dark cooling portion of the thermal cycling, resulting in greatly increased nonradiative recombination and current loss. Although carrier extraction is limited in the narrow band gap (NBG) mixed lead–tin perovskite subcell at low temperatures, this subcell is less prone to thermal instabilities under illumination, making it an attractive candidate for space power systems. Additionally, low-temperature photoluminescence (PL) and MPPT measurements are consistent with luminescence coupling between the WBG emission and NBG absorption, which is beneficial for increased power generation.

Deployment of photovoltaics in space requires devices that combine high‐efficiency, low areal mass, and resilience to harsh environments. Historically, high‐efficiency multijunction III–V materials have dominated space power systems; however, their high cost and limited manufacturing throughput motivate the exploration of scalable alternatives. While CdTe‐based thin‐film photovoltaics offer an attractive option, their performance on non‐conventional substrates can suffer from front contact instability under higher‐temperature processing. Here, the role of front contact chemistry in limiting cell performance is investigated using CdTe‐based devices fabricated on 150 μm thick Ceria‐doped space‐qualified 0214 Corning glass. A matrix of four transparent conducting oxides (TCOs: CTO, AZO, ITO, IZO) combined with two n‐type emitters (MZO, IGO) reveals chemical stability at the front interface—rather than absorber composition alone—governs recombination losses, voltage deficits, and device reproducibility. Chemically stable front contact combinations suppress elemental diffusion and interfacial degradation, resulting in significantly improved carrier lifetimes and junction quality. These insights are validated through record‐certified Cd(Se,Te) cell efficiencies of 18.4% under AM1.5G and 16.2% under AM0 illumination on ultra‐thin glass. Beyond CdTe, this work provides a general framework for the rational selection of TCO/emitter interfaces in superstrate thin‐film photovoltaics, including emerging technologies like metal halide perovskites, while enabling high‐efficiency, lightweight photovoltaics for space applications.

Here, we present the fabrication of a high‐quality Sb ₂ S ₃ absorber layer enabled by a thioacetamide (TA) based dual sulfur source combined with electron transport layer (ETL) chlorination. The chlorination, viz. CdCl ₂ heat treatment (CHT) is applied to CdS deposited over an industrially relevant inline‐processed SnO ₂ /FTO substrate. A systematic investigation of TA and CHT effects, focusing on oxygen, sulfur, and chlorine chemistry, shows that incorporating TA as an additional sulfur source significantly enhances the absorber microstructure by promoting larger grains, suppressing hk0 orientations, and improving grain growth along hk1 orientation while reducing trap density in the Sb ₂ S ₃ films. Simultaneously, ETL CHT enhances the structural, interface, and optoelectronic properties of CdS, improving the Sb ₂ S ₃ absorber quality as measured by average grain size and the preferred hk1 orientation. Most importantly, ETL CHT processing substantially reduces the absorber's oxygen content, thereby lowering the overall oxygen/sulfur ratio and suppressing deleterious SbO _x formation. The TA and ETL CHT combine to enable a PCE of 8.24% with a V _OC ‐deficit <950 mV. These findings demonstrate a promising, low‐temperature synthesis route to reduce oxygen content, helping to overcome a long‐standing barrier in achieving higher PCE.

Anisotropic optical properties of single crystal Al2O3 and atomic layer deposited (ALD) thin film alumina have been studied from 0.42 meV to 8.5 eV using spectroscopic ellipsometry. Generalized spectroscopic ellipsometry is used to obtain the complex dielectric function (ɛ = ɛ1 ± iɛ2) and complex refractive index (N = n + ik) spectra of Al2O3 single crystals for electric fields oscillating parallel (extraordinary) and perpendicular (ordinary) to the optic axis from the terahertz (THz) to vacuum ultraviolet (VUV) spectral ranges. Spectra in ɛ in the infrared (IR) spectral range show four transverse optical (TO) phonon modes at 385.5, 441.1, 568.6, and 633.1 cm−1 and four longitudinal optical (LO) phonon modes at 386, 481.5, 629, and 903.34 cm−1 along the ordinary direction. Two TO modes at 400.1 and 583.9 cm−1 and two LO phonon modes at 510.79 and 887.209 cm−1 are observed in the extraordinary direction. Birefringence is ∼0.011 in the near-IR to VUV and ∼0.34 in the THz spectral ranges. The refractive index (n) for amorphous ALD thin film alumina is smaller than that obtained for both directions of single crystal alumina, except from ∼6.8 to 7.6 eV where n for ALD alumina is greater due to an absorption onset at lower photon energies and Kramers–Kronig consistency. The single IR vibrational mode observed at 586 cm−1 for the ALD film is broader and has a smaller amplitude than that for all TO phonon modes observed for single crystal alumina along both principal directions.