Library · Signals, sensing & imaging
What Optoelectronic & Photovoltaic Probing got wrong, from 12 theses
Summary written by a model from the records below: The records evaluate experimental and analytical failures encountered during the probing and characterization of optoelectronic and photovoltaic systems. Across these studies, researchers experienced severe artifacts arising from probe-sample contact barriers, dynamic scanning response delays, measurement signal loss, and the breakdown of transport models. These records come from graduate theses, 2021 to 2025, each labeled with its degree where the repository states it, and each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Plus 10 problems the authors left open, listed at the end.
Failure modes, by theses reporting them
Select a mode to jump to its records.
Tip wear, contact barriers, and substrate constraints in electrical scanning probe microscopy
Scanning probe techniques suffered from rapid tip degradation, non-ideal interface barriers, and substrate-induced measurement blocks. Conductive AFM and scanning photocurrent microscopy encountered severe tip wear, surface oxidation, Schottky contact barriers with millisecond-to-second response times, and thick insulating diamond substrates preventing measurement.
Considered and rejected
Considered and rejected: Rejected using standard conductive AFM or SPCM due to non-ideal semiconductor-metal Schottky contact barriers and contact-limited millisecond-to-second response times
Imaging photo-carrier dynamics and correlated states in two-dimensional semiconductors · UT Austin · PhD
Considered and rejected
Considered and rejected: Backing plane electrodes on diamond for scanning probe microscopy, rejected because the thick insulating diamond substrate prevents conductive AFM (C-AFM) measurements.
Charge and Optical Stability of Color Centers in Diamond for Quantum Applications · University of Washington · PhD
Signal distortion and acquisition lag in high-speed and ultrafast scanning characterization
Fast scanning and time-resolved nanoscale probing suffered from instrumentation response limits and poor contrast. Switch response times, circuit capacitance, transducer vibrations, and reference standard impedance matching caused pulse distortion, missing pixel artifacts, and inadequate signal-to-noise ratios.
Tried and failed
photoconductively gated scanning tunneling microscopy applied to ultrafast time-resolved nanoscale measurements. Outcome: too slow. Reason: finite switch response time and circuit capacitance distorted electrical pulses, degrading temporal resolution
Ultrafast nanoscopy and multi-dimensional spectroscopy of processible photovoltaic materials · Imperial · PhD
Tried and failed
high-speed contact ultrasonic scanning applied to thin-film solar photovoltaic modules. Outcome: unstable. Reason: Transducer vibration and acquisition lag caused signal instability and missing pixel artifacts at higher scan speeds.
Ultrasonic guided waves for mechanical defects detection on thin-film solar photovoltaic modules · Georgia Tech · PhD
Tried and failed
scanning microwave microscopy admittance fitting applied to ultrathin 2D conductive films. Outcome: no signal. Reason: sample conductivity was too close to reference standard, leading to insufficient contrast and poor signal-to-noise ratio
QUANTITATIVE SCANNING MICROWAVE MICROSCOPY OF NANOELECTRONIC MATERIALS AND DEVICES · Cornell · PhD
Inaccuracies in electrical and electrochemical potential and carrier mobility extraction
Probing methods intended to track energy levels, charge transfer, and carrier mobility suffered from physical interference and charge neutrality effects. Open circuit potential failed to track minority carrier quasi-Fermi level splitting due to charge-neutral hole accumulation, optoelectrode charge-transfer resistance increased from polymer residue, and pulsed space-charge-limited current severely underestimated carrier mobilities.
Tried and failed
open circuit potential to track quasi-Fermi levels applied to semiconductor photoanodes during water oxidation. Outcome: no signal. Reason: hole accumulation is charge-neutral, preventing accurate tracking of minority carrier quasi-Fermi level splitting
Charge carrier accumulation and dynamics in metal oxide photoanodes · Imperial · PhD
Lost to a baseline
Charge-transfer resistance Rct of micro-/nano-optoelectrodes (190 kΩ) was higher than planar electrodes (81 kΩ) due to residual photoresist polymer residue.
Optical Nanoantennas Integrated with 3D Microelectrode Arrays: Hybrid Photonic-Electronic Modalities for Nano-Bio Interfacing · Virginia Tech · Master's
Tried and failed
pulsed voltage space-charge-limited current measurements applied to carrier mobility extraction in mixed ionic-electronic conductors. Outcome: worse than baseline. Reason: extracted carrier mobilities were underestimated by orders of magnitude compared to established values
The properties and consequences of mobile ionic defects in metal halide perovskites · Imperial · PhD
Breakdown of theoretical transport models in high-mobility and disordered semiconductors
Theoretical charge transport formulations failed to capture the empirical behavior of organic semiconductors and nanotube networks. Polaron transport models could not account for band-like conduction along high-mobility axes, while disorder-based models could not simultaneously reproduce charge-density-dependent mobility and temperature-independent Seebeck coefficients.
Tried and failed
Polaron transport theory applied to high-mobility large-bandwidth organic crystals. Outcome: did not generalise. Reason: Fails to capture band-like charge transport characteristics in large-bandwidth organic semiconductors along high-mobility axes
Charge transport and device engineering for improvement of thin film transistor · UT Austin · PhD
Tried and failed
Disorder-based transport models applied to semiconducting polymers and carbon nanotube networks. Outcome: did not generalise. Reason: Failed to simultaneously fit mobility charge-density dependence and temperature-independent Seebeck coefficient
Charge and Thermoelectric Transport in Semicrystalline Conjugated Polymers and Single-Walled Carbon Nanotube Networks · Cambridge · PhD
Convergence and parameter overestimation failures in transport and impedance equivalent circuit modeling
Equivalent circuit and numerical modeling frameworks produced severe numerical divergence or unphysical electrical parameters. Drift-diffusion equivalent circuit simulations failed to converge under high carrier injection, and standard Randles circuits with constant resistance overestimated double-layer discharge rates by orders of magnitude.
Tried and failed
equivalent circuit modeling of drift-diffusion equations applied to semiconductor charge carrier transport simulation. Outcome: did not converge. Reason: excess carrier densities exceeded baseline substrate doping by two orders of magnitude
A novel approach for SPICE modeling of light and radiation effects in ICs · EPFL · PhD
Considered and rejected
Considered and rejected: Rejected standard Randles EC with constant Rct because it overestimates double-layer discharge rates by orders of magnitude compared to experiments.
Aspects of dynamics in proton exchange membrane water electrolysis · Leibniz Universität Hannover · PhD
Left open by the authors
Problems the authors named and did not get to.
Left open
Characterise electrolyte solution ions via ICP-MS to determine the exact redox reaction mechanism and two-phase discharge profile. Blocker: Requires wet-lab access, chemical samples, and an ICP-MS instrument
Ion-selective membranes for hydrogen-metal hybrid redox flow batteries · Imperial · Doctorate
Left open
Optimize VTD deposition parameters and precursor conversion to eliminate hysteresis and increase perovskite solar cell power conversion efficiency. Blocker: Requires physical vapor transport deposition hardware, chemical precursors, and photovoltaic characterization lab equipment.
Vapor Transport Deposition for Perovskite Solar Cells · MIT · PhD
Left open
Determine whether 2D perovskite capping layers are fundamentally essential or a transitory optimization trend for PSC technology. Blocker: Requires long-term photovoltaic device fabrication, experimental characterization, and physical wet lab testing
Interfacial Engineering: The Key to Boost Perovskite Solar Cells Performance and Stability · EPFL · PhD
Left open
Upscale perovskite photovoltaic device fabrication to larger substrates while suppressing J-V hysteresis and improving stability. Blocker: Requires a physical materials synthesis and device fabrication laboratory.
Low Dose Analytical Electron Microscopy of Hybrid Perovskite Photovoltaic Devices · Cambridge · PhD
Left open
Optimize transport layers, engineer perovskite interfaces, and apply passivation layers to minimize series resistance and charge recombination. Blocker: Requires a physical materials synthesis and device fabrication laboratory equipped for vapor deposition and perovskite processing.
Fabricating and Tailoring Halide Perovskites for Photovoltaic Applications · MIT · PhD
Left open
Investigate the mechanism of the persistent residual charge transfer state recombination in PbS:2,6-F-CA-/PDI beyond 1.8 ns using transient absorption spectroscopy. Blocker: Requires wet lab chemical synthesis and ultrafast transient absorption spectroscopy apparatus.
Designing nanocrystal donor : molecular acceptor interfaces for improved charge and energy transfer · UT Austin · PhD
Left open
Resolve S-shaped double diode degradation under thermal aging in polythiophene hole transport layers for perovskite solar cells. Blocker: Requires a wet chemistry and photovoltaic device fabrication/testing laboratory to synthesize and age devices.
Scalable Perovskite Thin-Film Photovoltaics · MIT · PhD
Left open
Optimize perovskite solar cell architectures using Me-4PACz hole transport layers, narrower bandgap absorbers below 1.63 eV, and anti-reflective coatings. Blocker: Requires a wet chemistry and vapor deposition laboratory to fabricate and test physical photovoltaic devices.
Vapor Deposition of Perovskite Solar Cells · EPFL · PhD
Left open
Optimize the thickness of the TiO2 layer in monolithic perovskite solar cells to enhance charge transfer. Blocker: Requires a wet lab and fabrication/characterization equipment for solar cells.
INDIGENOUS DEVELOPMENT OF DYE-SENSITIZED SOLAR CELLS AND PERFORMANCE EVALUATION UNDER TEXAS ENVIRONMENT · West Texas A&M University · Master's
Left open
Perform wavelength-dependent surface photovoltage measurements on the tetracene/passivation/silicon interface to determine interfacial charge transfer dynamics and polarity. Blocker: Requires fabricated physical photovoltaic bilayer samples and a surface photovoltage spectroscopy laboratory setup.
Who has worked on this
Authors of the public theses cited on this page, most-cited first.
- Louise Ilena Oldham · Imperial · PhD · 2025
Charge carrier accumulation and dynamics in metal oxide photoanodes - Tamar Kadosh Zhitomirsky · MIT · PhD · 2025
Fabricating and Tailoring Halide Perovskites for Photovoltaic Applications - Narumi Nagaya · MIT · PhD · 2025
Singlet exciton fission-enhanced silicon photovoltaics: Interfacial engineering, device design and spectroscopic technique development - Tobias Krenz · Leibniz Universität Hannover · PhD · 2025
Aspects of dynamics in proton exchange membrane water electrolysis - Haoqing Ning · Imperial · PhD · 2024
Ultrafast nanoscopy and multi-dimensional spectroscopy of processible photovoltaic materials - Xiaopeng Wang · Cornell · PhD · 2024
QUANTITATIVE SCANNING MICROWAVE MICROSCOPY OF NANOELECTRONIC MATERIALS AND DEVICES - Christian Bernat Pederson · University of Washington · PhD · 2024
Charge and Optical Stability of Color Centers in Diamond for Quantum Applications - Elieser A. Mejia · Virginia Tech · Master's · 2024
Optical Nanoantennas Integrated with 3D Microelectrode Arrays: Hybrid Photonic-Electronic Modalities for Nano-Bio Interfacing - Luke Petit · Imperial · Doctorate · 2023
Ion-selective membranes for hydrogen-metal hybrid redox flow batteries - Dicky Januarizky Silitonga · Georgia Tech · PhD · 2023
Ultrasonic guided waves for mechanical defects detection on thin-film solar photovoltaic modules - Ella Louise Wassweiler · MIT · PhD · 2023
Vapor Transport Deposition for Perovskite Solar Cells - Quentin Jean-Marie Armand Guesnay · EPFL · PhD · 2023
Vapor Deposition of Perovskite Solar Cells
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