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Nahar, Aayush

Publications and source records attributed to Nahar, Aayush.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Impacts of Non-Ideal Back Contact on Capacitance Measurements in CdTe Solar Cells

CdTe solar cells suffer from a non-ideal back contact which can strongly affect the equivalent circuit model and complicate capacitance measurements. Here, five different back contact materials are deposited on identical CdTe absorbers and their influence on capacitance measurements is characterized. A five-element equivalent circuit model is shown to represent a CdTe solar cell with a non-ideal back contact, and capacitance-frequency (C-f) measurements on each sample clearly show the influence of this contact. Capacitance-voltage (C-V) measurements on each sample show the influence of frequency on measured capacitance. In the AlGaOx/Au sample, temperature dependent C-fs show the back barrier height to be 240 meV, and ongoing measurements will give a comparison of back barrier heights for all samples. This study provides insight into the efficacy of various back contacts and highlights potential errors in the interpretation of capacitance measurements due to the presence of the back contact.

cadmium compounds↗
DOE OSTI2024

Optimization of Sb-doped CdSeTe Solar Cells

The effect of high-temperature annealing (HTA) treatments and Cd-excess during the in-situ doping of CdSeTe:Sb is investigated. Optimized treatments eliminate the wurtzite phase from the as-deposited CdSeTe layer, while facilitating Se intermixing and grain size enhancement before CdCl2 treatment. The improved device stack quality results in a VOC improvement of 250 mV. VOC is further improved by tuning the Cd/Sb flux ratio during CdSeTe:Sb deposition. The lowest defect concentration is achieved at Cd/Sb of 1.4:1, which produced the best VOC CdSeTe:Sb cell with VOC = 849mV, despite a decreased carrier concentration due to the harsh CdCl2 treatment.

14 SOLAR ENERGY↗
DOE OSTI2024

Impacts of Non-Ideal Back Contact on Capacitance Measurements in CdTe Solar Cells

CdTe solar cells suffer from a non-ideal back contact which can strongly affect the equivalent circuit model and complicate capacitance measurements. Here, five different back contact materials are deposited on identical CdTe absorbers and their influence on capacitance measurements is characterized. A five-element equivalent circuit model is shown to represent a CdTe solar cell with a non-ideal back contact, and capacitance-frequency (C-f) measurements on each sample clearly show the influence of this contact. Capacitance-voltage (C-V) measurements on each sample show the influence of frequency on measured capacitance. In the AlGaOx/Au sample, temperature dependent C-fs show the back barrier height to be 240 meV, and ongoing measurements will give a comparison of back barrier heights for all samples. This study provides insight into the efficacy of various back contacts and highlights potential errors in the interpretation of capacitance measurements due to the presence of the back contact.

14 SOLAR ENERGY↗
DOE OSTI2023

Pyrolyzer Assisted Vapor Transport Deposition of Antimony-doped Cadmium Telluride

A new method for in-situ Sb doping of CdTe that uses a modified vapor transport deposition system is described. This modification enables control of the Sb concentration with a pyrolysis stage to enhance the doping efficiency. CdTe:Sb films under different deposition conditions are characterized by SEM, XRD, and CV measurements for determining morphology, crystal structure, and hole concentration. Variations of the Sb dopant heater and pyrolyzer temperatures do not affect the CdTe morphology and crystal structure. However, CV measurements show that a higher dopant heater or pyrolyzer temperature leads to higher hole concentration. In this study, CdTe: Sb films achieve a hole concentration of 1016 cm-3 and 10% doping efficiency when the dopant heater is 600C and the pyrolyzer temperature is 1100C. This demonstrates a path to produce high hole concentration polycrystalline CdTe film with a low concentration of dopant-induced defect.

14 SOLAR ENERGY↗